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Purpose: Registry data shows that less surgeons are resurfacing the patella during total knee arthroplasty (TKA). This tendency highlights the importance of matching trochlear and native patellar anatomy. Currently, there is a lack of consensus on implant design that best accommodates native patellae. The objective of this study was to compare the trochlear morphology of a large selection of contemporary TKA designs with the native trochlear anatomy., Methods: Three-dimensional models of 13 femoral component designs from seven manufacturers and 37 healthy human femora (average age: 31.2 ± 13.4 years) were reconstructed. The trochlear morphology, including trochlear length, sulcus angle, trochlear groove angle, and height and width of the medial and lateral facets, was measured along the trochlea at 15° increments., Results: The prosthetic trochlea was shorter and shallower compared to the native trochlea (p < 0.01). The native trochlea was bilinear and had a medial orientation proximally, whereas all asymmetrical TKA designs had a laterally oriented trochlea, resulting in opposite trochlear groove orientation (TKA, 5.8 ± 3.7°; native -3.1 ± 4.1°, p < 0.001). In addition, a strong correlation (R 2  = 0.89) was found in TKA models between the heights of the medial and lateral facets, which was not observed for the native femora (R 2  = 0.06)., Conclusion: This study highlights that the lateral trochlear orientation in existing TKA models is not anatomical. Given the rising trend in patellar non-resurfacing during TKA, further studies are necessary to improve trochlear design that better accommodates the native patellar morphology., Competing Interests: Declarations. Conflict of interest: Dr. David Rodriguez-Quintana is a speaker and paid consultant for Zimmer Biomet. Dr. Shuyang Han serves on the editorial board of the Journal of Arthroplasty and BMC Musculoskeletal Disorders. Dr. Han is also a committee member for the Orthopaedic Trauma Association. All other authors (Gattu, Doherty, He, Ismaily, Lanfermeijer, Pletka) declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Ethical approval: All procedures involving human participants were in accordance with the ethical standards of the institutional and/or national research committee, as well as the 1964 Helsinki Declaration and its subsequent amendments or equivalent ethical standards., (© 2024. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Purpose: The medial synovial fold of the posterior cruciate ligament is one of the synovial plicae of the knee joint. The objective of this study was to assess the necessity of reporting the appearance of the medial synovial fold of the posterior cruciate ligament on magnetic resonance imaging of the knee joint and its correlation with side and sex., Methods: Patients with normal knee structure on magnetic resonance imaging (MRI) scans between 2018 and 2023 were included in this retrospective study. MRI scans of the knee joints were retrospectively reviewed by two musculoskeletal radiologists independently. The medial synovial fold of the posterior cruciate ligament was divided into three types according to the imaginary line drawn between the lateral border of the medial femoral condyle and the medial tibial intercondylar tubercle., Results: The study included 1147 patients, of whom 478 (41.7%) were female and 669 (58.3%) were male. Among these patients, 580 (50.6%) had a right knee scan, and 567 (49.4%) had a left knee scan. The age range was 15-35 years for both sexes. The frequency of the medial synovial fold types in all patients was as follows: Type A (30.1%), Type B (55.4%) and Type C (14.5%). There was a high level of agreement between the observers. There was a statistically significant difference in the frequency of medial synovial fold types between sexes, with men exhibiting a greater prevalence., Conclusion: Magnetic resonance imaging (MRI) of the knee joint revealed the medial synovial folds of the posterior cruciate ligament (PCL). The most common was Type B (55.4%), followed by Type A (30.1%) and Type C (14.5%) among the MSF types. No statistically significant difference was found between the right and left knees for any of the MSF types., (© 2024. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

In designing femoral components, which restore native (i.e., healthy) knee kinematics, the flexion-extension (F-E) axis of the tibiofemoral joint should match that of the native knee. Because the F-E axis is governed by the curvature of the femoral condyles in the sagittal plane, the primary objective was to determine the variation in radii of curvature. Eleven high accuracy three-dimensional (3D) femur models were generated from ultrahigh resolution CT scans. The sagittal profile of each condyle was created. The radii of curvature at 15 deg increments of arc length were determined based on segment circles best-fit to ±15 deg of arc at each increment. Results were standardized to the radius of the best-fit overall circle to 15 deg-105 deg for the femoral condyle having a radius closest to the mean radius. Medial and lateral femoral condyles exhibited multiradius of curvature sagittal profiles where the radius decreased at 30 deg flexion by 10 mm and at 15 deg flexion by 8 mm, respectively. On either side of the decrease, radii of segment circles were relatively constant. Beyond the transition angles where the radii decreased, the anterior-posterior (A-P) positions of the centers of curvature varied 4.8 mm and 2.3 mm for the medial and lateral condyles, respectively. A two-radius of curvature profile approximates the radii of curvature of both native femoral condyles, but the transition angles differ with the transition angle of the medial femoral condyle occurring about 15 deg later in flexion. Owing to variation in A-P positions of centers of curvature, the F-E axis is not strictly fixed in the femur., (Copyright © 2024 by ASME.)

Background: The literature does not clearly convey the relationship between eminential morphometry and non-contact anterior cruciate ligament (ACL) ruptures. This study attempts to reveal whether there is a relationship between non-contact ACL ruptures and eminential morphometry., Methods: Knee magnetic resonance images (MRIs) taken for the various indications between January 2022 and June 2023 were retrospectively scanned. The patients were categorized into 2 groups: those with an ACL rupture and those with an intact ACL. For each patient, eminential angle 1, eminential angle 2, medial eminential height, lateral eminential height, total eminential height, eminential width, and the ratio of tibial plateau width and eminential width to the tibial plateau width were measured by 2 different orthopedists. Patients whose MRIs were used for measurement were evaluated and grouped according to their age, sex, and injury side., Results: In total, 400 MRIs of 400 patients were included in the study. While 200 patients had an ACL rupture, 200 had an intact ACL. The total eminential height in the ACL rupture group was measured at 16.1 ± 2.6 mm and 15.5 ± 2.7 mm (p = 0.035) in the ACL intact group. Eminental width in the ACL rupture group was measured at 12.1 ± 1.9 mm and 13.0 ± 2.0 mm in the ACL intact group (p = 0.0001). The tibial plateau width was 75.4 ± 15.7 mm in the ACL rupture group and 73.6 ± 5.8 mm in the ACL intact group (p = 0.002). According to the logistic regression analysis, the p-value for males was 0.0001, and for eminential width, the p-value was 0.0001., Conclusions: A significant difference was found between the ACL rupture and the ACL intact groups regarding eminential height, eminential width, and tibial plateau width parameters. Being male and having a low eminential width were identified as independent risk factors for non-contact ACL., Trial Registration: Not applicable., (© 2024. The Author(s).)

Knee arthroplasty technique is constantly evolving and the opportunity for surgeons to practice new techniques is currently highly dependent on the availability of cadaveric specimens requiring certified facilities. The high cost, limited supply, and heterogeneity of cadaveric specimens has increased the demand for synthetic training models, which are currently limited by a lack of biomechanical fidelity. Here, we aimed to design, manufacture, and experimentally validate a synthetic knee surgical training model which reproduces the flexion dependent varus-valgus (VV) and anterior-posterior (AP) mechanics of cadaveric knees, while maintaining anatomic accuracy. A probabilistic finite element modeling approach was employed to design physical models to exhibit passive cadaveric VV and AP mechanics. Seven synthetic models were manufactured and tested in a six-degree-of-freedom hexapod robot. Overall, the synthetic models exhibited cadaver-like VV and AP mechanics across a wide range of flexion angles with little variation between models. In the extended position, two models showed increased valgus rotation (<0.5°), and three models showed increased posterior tibial translation (<1.7 mm) when compared to the 95% confidence interval (CI) of cadaveric measurements. At full flexion, all models showed VV and AP mechanics within the 95% CI of cadaveric measurements. Given the repeatable mechanics exhibited, the knee models developed in this study can be used to reduce the current reliance on cadaveric specimens in surgical training., (© 2024 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals LLC on behalf of Orthopaedic Research Society.)

Background: The coronal plane alignment of the knee (CPAK) classification system divides coronal knee anatomy into 9 phenotypes, suggesting different soft tissue balancing is needed for optimal outcomes. We investigated the interplay between CPAK phenotypes and gap stress curves throughout the knee's range of motion, aiming to understand their impact on total knee arthroplasty balancing., Methods: There were 1,112 total knee arthroplasty cases from 2 imageless robotic assisted navigation systems using posterior stabilized implants that were classified into CPAK phenotypes. Medial and lateral initial gap values were measured throughout the knee flexion-extension arc, gap curve morphologies were generated, and mediolateral (ML) gap balance was calculated for each phenotype. The most common phenotypes were included in this study, CPAK I to VI., Results: Each phenotype exhibited a distinct gap curve morphology. Type I maintained the largest ML gap difference (-3.6 to -2.1), with the medial compartment tightest in extension. Type II showed relative laxity in the lateral compartment compared to the medial gap (-1.0 to -1.9), with the medial compartment tightening through flexion. Type III had a looser medial and tighter lateral compartment in extension that inverts to a tighter medial compartment in deep flexion (2.1 to -0.8), while Type IV showed a decreasing compartment difference with increased flexion (-3.7 to 0.6). Type V had fluctuating tightness (-0.6 to 1.8), and Type VI had the medial compartment tightening more with flexion (0.6 to 1.8)., Conclusions: The distinct stress curves and ML gap behavior provide a "fingerprint" for each corresponding CPAK phenotype. Investigating these morphologies can help determine the best phenotype-specific treatments, including alignment strategy, implant selection, and gap balance, for optimal functional and patient outcomes., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background and Objective: The BOne Strength (BOS) score is a CT-based tool to assess fracture risk for patients with femoral bone metastases using finite element (FE) models. Until now, the knee joint center (KJC) and centers of the condyles (CoCs) were needed to create the FE model, hence BOS scores of incompletely scanned femurs could not be calculated. In this study, a statistical shape model (SSM) was used to align FE models of femurs with a removed knee anatomy. The aim was to determine the effect of using an SSM with different proximal femur fractions on KJC and CoC locations, and on the BOS score., Methods: QCT scans of 117 femurs were used to generate patient-specific FE models of the proximal femur. These models were aligned using the knee joint center (KJC), center of condyles (CoC) and femoral head center. The femurs were artificially shortened by removing 30 %, 50 % or 70 % of the femur. A recently developed SSM was used to reconstruct the distal femur. For each of the femur fractions, the difference between the original and SSM-reconstructed KJC and CoC were determined and the BOS scores were calculated., Results: Although the individual differences between the original and SSM-reconstructed KJC and CoC location could be large, the effect on the individual BOS scores was limited. The SSM-reconstructed BOS scores were highly correlated to the original BOS scores., Conclusion: Using SSM to align femurs with a removed knee anatomy resulted in varying estimation of knee anatomy between patients but relatively accurate BOS scores., Competing Interests: Declaration of competing interest None declared., (Copyright © 2024. Published by Elsevier B.V.)

Introduction: The current study, which delves into proximal tibia morphometric parameters in a Greek sample, not only analyzes whether specific linear distance ratios are consistent but also paves the way for a potential novel metric system for knee arthroplasty imaging studies using constant ratios. These findings could have significant implications for future enlarged research and clinical practice., Methods: A total of 38 dried tibiae were evaluated by two independent investigators. The following distances were measured with a digital Vernier sliding caliper: (1) the mediolateral distance of the proximal surface (A), (2) the anteroposterior distance of the proximal surface (B), (3) The longitudinal length of the bone (C), (4) the line connecting the anterior margin of the proximal surface with the highest peak of the tibia tuberosity (D), (5) the depth of the proximal margin of the medial articular facet (AF) (medial plateau) (E) and (6) the depth of the proximal margin of the lateral AF (lateral plateau) (F)., Results: The A, B, C, D, E, and F mean distances were 71.3 mm, 47.4 mm, 340.2 mm, 37.1 mm, 42 mm, and 35.9 mm. Reliability analysis for each observer on all measurements revealed an interclass correlation (ICC) score of 0.975 (observer 1) and 0.971 (observer 2). The ratio A/B was 1.5, A/C was a constant 0.2, and D/C was 0.1. The ratio E/F was 1.2. The six measurements (A-F) showed excellent inter-observer reliability (all ICC values > 0.990)., Conclusions: The study established constant ratios of the studied linear distances around the proximal tibia. Considering these ratios, asymmetrical tibial components in knee arthroplasty seem to replicate the native anatomy more closely. Furthermore, the distance from the anterior margin of the proximal surface to the tibial tuberosity peak, constituting one-tenth of the longitudinal length of the tibia, shows promise as a metric system for imaging studies, especially in assessing lesions around tibial components., (© 2024. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Purpose: The suprapatellar bursa is located in the proximal deep layer of the patella and is thought to reduce tissue friction by changing from a single-membrane structure to a double-membrane structure during knee joint motion. However, the dynamics of the suprapatellar bursa have only been inferred from positional relationships, and the actual dynamics have not been confirmed., Methods: Dynamics of the suprapatellar bursa during knee joint motion were observed in eight knees of four Thiel-fixed cadavers and the angle at which the bursa begins to show a double membrane was revealed. The flexion angles of knee joints were measured when the double-membrane structure of the suprapatellar bursa began to appear during knee joint extension., Results: The suprapatellar bursa changes from a single membrane to a double-membrane structure at 91 ± 4° of flexion, when the knee joint is moved from a flexed position to an extended position., Conclusion: The suprapatellar bursa may be involved in limitations to knee joint range of motion and pain at an angle of approximately 90°. Further studies are needed to verify whether the same dynamics are observed in living subjects., (© 2024. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Background: Dissatisfaction after total knee arthroplasty (TKA) ranges from 15 to 30%. While patient selection may be partially responsible, morphological and reconstructive challenges may be determinants. Preoperative computed tomography (CT) scans for TKA planning allow us to evaluate the hip-knee-ankle axis and establish a baseline phenotypic distribution across anatomic parameters. The purpose of this cross-sectional analysis was to establish the distributions of 27 parameters in a pre-TKA cohort and perform threshold analysis to identify anatomic outliers., Methods: There were 1,352 pre-TKA CTs that were processed. A 2-step deep learning pipeline of classification and segmentation models identified landmark images and then generated contour representations. We used an open-source computer vision library to compute measurements for 27 anatomic metrics along the hip-knee axis. Normative distribution plots were established, and thresholds for the 15th percentile at both extremes were calculated. Metrics falling outside the central 70th percentile were considered outlier indices. A threshold analysis of outlier indices against the proportion of the cohort was performed., Results: Significant variation exists in pre-TKA anatomy across 27 normally distributed metrics. Threshold analysis revealed a sigmoid function with a critical point at 9 outlier indices, representing 31.2% of subjects as anatomic outliers. Metrics with the greatest variation related to deformity (tibiofemoral angle, medial proximal tibial angle, lateral distal femoral angle), bony size (tibial width, anteroposterior femoral size, femoral head size, medial femoral condyle size), intraoperative landmarks (posterior tibial slope, transepicondylar and posterior condylar axes), and neglected rotational considerations (acetabular and femoral version, femoral torsion)., Conclusions: In the largest non-industry database of pre-TKA CTs using a fully automated 3-stage deep learning and computer vision-based pipeline, marked anatomic variation exists. In the pursuit of understanding the dissatisfaction rate after TKA, acknowledging that 31% of patients represent anatomic outliers may help us better achieve anatomically personalized TKA, with or without adjunctive technology., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Anatomic referencing in total knee arthroplasty places the femoral component flush to the anterior cortex while maintaining posterior condylar offset (PCO). The intent of this study was to evaluate how component position influences the femoral component size., Methods: Digital surface models were created using 446 femora from an established computed tomography database. Virtual bone resections, component sizing, and component placement were performed assuming neutral (0°) flexion and neutral (3°) rotation relative to the posterior condyles. The appropriately sized femoral component, which had 2 mm of incremental size, was placed flush with the anterior cortex for optimal restoration of the PCO. Sizing and placement were repeated using 3 and 6° flexion and 0, 5, and 7° external rotation (ER)., Results: At 0° flexion, decreasing ER from 3 to 0° resulted in an average decreased anterior-posterior height (APH) of 1.9 mm, corresponding to a component size decrease of 1 for 88% of patients. At 7° ER, component size increased by an average of 2.5 mm, corresponding to a size increase for 80% of patients. Flexing the femoral component to 3° with ER at 3° resulted in a decrease in APH of 2.2 mm (1 size decrease in 93% of patients). At 3° flexion and 3° ER, 86% had the same component size as at 0° flexion and 0° ER. Increasing ER at 3° flexion increased APH by 1.2 mm at 5° and 3.1 mm at 7° on average, relative to 3° ER. Increasing flexion from 3 to 6° extended this effect., Conclusions: Flexion decreases the APH when the ER is held constant. The ER of the femoral component increases the APH across all tested flexion angles, causing an increase in the ideal femoral component size to maintain PCO. With anatomic referencing, alterations in femoral component positioning and subsequent changes in component size can be accounted for., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Statistical shape models (SSMs) are useful tools in evaluating variation in bony anatomy to assess pathology, plan surgical interventions, and inform the design of orthopaedic implants and instrumentation. Recently, by considering multiple bones spanning a joint or the whole lower extremity, SSMs can support studies investigating articular conformity and joint mechanics. The objective of this study was to assess tradeoffs in accuracy between SSMs of the femur or tibia individually versus a combined joint-level model. Three statistical shape models were developed (femur-only, tibia-only, and joint-level) for a training set of 179 total knee arthroplasty (TKA) patients with osteoarthritis representing both genders and several ethnicities. Bone geometries were segmented from preoperative CT scans, meshed with triangular elements, and registered to a template for each SSM. Principal component analysis was performed to determine modes of variation. The statistical shape models were compared using measures of compactness, accuracy, generalization, and specificity. The generalization evaluation, assessing the ability to describe an unseen instance in a leave-one-out analysis, showed that errors were consistently smaller for the individual femur and tibia SSMs than for the joint-level model. However, when additional modes were included in the joint-level model, the errors were comparable to the individual bone results, with minimal additional computational expense. When developing more complex SSMs at the joint, lower limb, or whole-body level, the use of an error threshold to inform the number of included modes, instead of 95 % of the variation explained, can help to ensure accurate representations of anatomy., Competing Interests: Competing interests William Fugit and Riza Bayoglu have no conflicts of interest. Luke Aram was an employee of DePuy Synthes. Peter Laz received institutional research support from DePuy Synthes., (Copyright © 2024. Published by Elsevier Ltd.)

Purpose: The purpose of this study was to determine whether significant differences exist when comparing posterior tibial slope (PTS) measured using increasing lengths of the tibia to determine the anatomical axis., Methods: Patients with full-length weight-bearing tibial radiographs were retrospectively identified from 2014 to 2022 at a single institution. Patients were excluded if there was any previous history of lower extremity fracture or osteotomy. The anatomical axis of the tibia was determined using the full length of tibial radiographs, and the "reference PTS" was measured using this axis. Using the same radiograph, the PTS was measured using four different anatomical axes at standardized tibial lengths. While the center of the proximal circle remained constant at 5-cm below the tibial plateau, the center of the distal circle was drawn at four points: a) overlapping circles; b) 10-cm distal to the tibial plateau; c) 15-cm distal to the tibial plateau; d) half the length of the tibia, measured from the tibial plateau to the tibial plafond. Bivariate correlation and frequency distribution analysis (measurements >2-degrees from reference PTS) were performed between the reference PTS and PTS measured at each of the four other lengths., Results: A total of 154 patients (39.8 ± 17.4 years old, 44.2% male) were included in the final analysis. Measurements at each of the four tibial lengths were all significantly different from the reference PTS (p < 0.001). The correlation strength improved with increasing tibial length (overlapping: R = 0.681, 10-cm: R = 0.821, 15-cm: R = 0.937, and half-tibia: R = 0.963). The number of PTS measurements >2-degree absolute difference from the reference PTS decreased with increasing tibial length (overlapping: 40.3%, 10-cm: 24.0%, 15-cm: 26.0%, and half-tibia: 18.8%)., Conclusion: Assessment of PTS is dependent on the length of the tibia utilized to obtain the anatomical axis. Accuracy and precision of PTS measurements improved with increasing length of tibia used to determine the anatomical axis., Study Design: Case series., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Measurements of knee cartilage thickness derived from MR images are attractive biomarkers for osteoarthritis research. Although some cross-sectional multivendor studies exist, none have employed fully automatic three-dimensional MRI analysis. Our objective was to evaluate the variations in knee cartilage thickness measurements obtained using automated methods and MRI instruments from five different vendors., Methods: The subjects were 10 healthy volunteers aged 22-60 years. MRI models with 3 Tesla strength from five different companies were used. Cartilage thickness was quantified fully automatically for seven regions. We hypothesized that "the MRI model influences cartilage thickness measurements." Inter-measurement error, defined as the absolute difference between the targeted and median thicknesses determined by the five MRI models, was analyzed using histograms. The factors generating the largest inter-measurement error were also examined., Results: No exceptional trends attributable to a specific instrument model were observed, and the p-value from the Kruskal-Wallis test exceeded 0.05 in all seven regions. Therefore, the study hypothesis was rejected. Of the 350 measurements, the inter-measurement error was ≤0.05 mm in 53 %, ≤0.10 mm in 75 %, and ≤0.20 mm in 95 %. Analysis of the medial tibial cartilage, which had the largest inter-measurement error, revealed mis-extraction of synovial fluid as cartilage., Conclusions: The choice of MRI model did not influence cartilage thickness measurements. Overall, 95 % of the inter-measurement errors were within 0.20 mm. The greatest error resulted from mis-extracting synovial fluid as cartilage., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Ichiro Sekiya reports financial support was provided by Fujifilm Holdings Corporation. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Objective: Obtaining an optimal knee skyline view is challenging due to inaccuracies in beam projection angles (BPAs) and soft tissue obscuring bony landmarks. This study aimed to assess the impact of BPA deviations on patellofemoral index measurements and assessed the anterior border of the proximal tibia as an anatomic landmark for guiding BPAs., Materials and Methods: This retrospective study consisted of three parts. The first was a simulation study using 52 CT scans of knees with a 20° flexion contracture to replicate the skyline (Laurin) view. Digitally reconstructed radiographs simulated neutral, 5° downward, and 5° upward tilt BPAs. Five patellofemoral indices (sulcus angle, congruence angle, patellar tilt angle, lateral facet angle, and bisect ratio) were measured and compared. The second part was a proof of concept study on 162 knees to examine patellar indices differences across these BPAs. Lastly, the alignment of the anterior border of the proximal tibia with the BPA tangential to the patellar articular surface was tested from the CT scans., Results: No significant differences in patellofemoral indices were found across various BPAs in both the simulation and proof of concept studies (all p > 0.05). The angle between the anterior border of the proximal tibia and the patellar articular surface was 1.5 ± 5.3°, a statistically significant (p = 0.037) yet clinically acceptable deviation., Conclusion: Patellofemoral indices in skyline view remained consistent regardless of BPA deviations. The anterior border of the proximal tibia proved to be an effective landmark for accurate beam projection., (© 2024. The Author(s).)

One of the critical steps in total knee arthroplasty is femoral component positioning and sizing. Historically, there was wider variability between femoral component sizes, necessitating the concepts of anterior referencing (AR) and posterior referencing (PR). With the introduction of smaller increments between sizes, the concept of anatomic referencing has been introduced to replace AR and PR. The intent of this study was to validate the concept of anatomic referencing and show that with 2 mm increments in femoral sizes, the femoral component can be placed flush to the anterior cortex while maintaining posterior condylar offset (PCO). Digital surface models were created using 515 femurs from an established computed tomography database. Virtual bone resections, component sizing and placement were performed assuming neutral mechanical axis and a cartilage thickness of 2 mm. The appropriately sized femoral component, which had 2 mm incremental sizes, was placed flush with the anterior cortex with restoration of the PCO. The anterior-posterior distance from the posterior surface of the component to the medial and lateral surfaces of the posterior condylar cartilage were measured. The medial condyle was the limiting condyle in the majority of cases (73%). The average medial gap after appropriate femoral component matching was 0.6 mm (0.39-1.41 mm) across all sizes. The overall average condylar gap was 1.02 mm. The most common femoral component was a size 7 (57.2 mm) and the average femoral AP width was 55.9 mm. Anatomic referencing with an implant system that has 2-mm increments in femoral component sizing provides an alternative to AR and PR without compromise. Anatomic referencing allows for perfect alignment of the anterior flange of the femoral component to the anterior cortex of the femur while restoring the native PCO to within 1 mm. This avoids having to choose between AR or PR when in between femoral sizes., Competing Interests: J.B. reports being a board member of Orthopaedic Research Society. Stocks Zimmer Biomet. G.R.S. reports royalties from Zimmer Biomet. Consulting fee from Zimmer Biomet, 3M KCI, and Canary. Payment or honoraria from Zimmer Biomet and 3M KCI. Participation on a Advisory Board of Canary and Enhanced Medical Nutrition. Stocks of ROM Tech, KAT Robotics, and Enhanced Medical Nutrition., (Thieme. All rights reserved.)

The posterolateral region of the knee has a complex and diverse anatomy. Hydrarthrosis of the knee can potentially communicate with other parts of the joint space. The joint fluid distribution reflects anatomical communications between synovial spaces. To observe the continuity between the knee joint cavity and the surrounding bursa, we devised a dissection method with a new injection agent, an eosin-containing congealed liquid that spreads uniformly over the entire space. The purpose of this study was to perform a detailed examination of the subpopliteal recess (SPR) where a bursa connects to the knee joint capsule. We also reported the advantages of this new injection agent compared with conventional materials (latex and epoxy resin). Twenty-two formalin-fixed cadavers (34 knees), two N-vinyl-pyrrolidone (NVP)-fixed cadavers (4 knees), and two cadavers (3 knees) fixed by Thiel's method were used. After filling the knee joint space and SPR with eosin congealed liquid, the specimens were dissected to investigate the morphology of the SPR. In addition, three different types of injection agents were assessed. The SPR extended distally along the popliteus tendon. The SPR length was 22.64 ± 11.38 mm from the upper end of the lateral tibial condyle to the lower end of the depression. The existence of a fabellofibular ligament made the SPR significantly longer, but abrasion of the femoral articular cartilage did not affect the SPR. Furthermore, the relationship between the popliteus muscle and the SPR was classified into three types (types 1-3). Types 2 and 3 in which the SPR extended to the proximal tibiofibular joint may cause instability of the knee joint. The eosin congealed liquid was highly useful in many aspects, such as fluidity and injection workability. The new dissection method with eosin congealed liquid provides insights into the anatomy of the posterior lateral knee, which are useful for radiological diagnoses and clinical treatments., (© 2024 American Association of Clinical Anatomists and British Association of Clinical Anatomists.)

Background: The morphology of the trochlear compartment of total knee arthroplasty (TKA) prostheses is a major determinant of postoperative patello-femoral kinematics, particularly with unresurfaced patellae. The objective of this study was to quantify and compare the trochlear morphology of a large series of contemporary and legacy TKA designs., Methods: The 3-dimensional surface models of 22 femoral components (13 contemporary and 9 legacy) were created using high-resolution laser scanning. The trochlear profile of each component was analyzed from proximal to distal in 15° increments around the trochlear axis. In each profile, the following variables were measured: sulcus angle, medio-lateral deviation of the sulcus, the height and width of the facets, and the trochlear groove orientation., Results: In the contemporary group, the sulcus angle decreased progressively along the trochlear arc to varying degrees, except for 2 symmetrical designs, whereas the sulcus angle of the legacy designs showed considerable variability. The height of the medial facet was very strongly correlated with that of the lateral facet in the contemporary group (R 2  = 0.89), whereas the correlation was weak for the legacy designs (R 2  = 0.36). Moreover, the trochlear sulcus deviated laterally from distal to proximal in 10 contemporary designs and 7 legacy designs, resulting in a trochlear groove orientation of 4.2 to 11.1° and 4.3 to 10.5°, respectively. In the remaining 5 designs (3 contemporary and 2 legacy), the sulcus was vertical., Conclusions: There is more consistency in trochlear morphology of contemporary TKA designs compared to that of legacy designs, yet there are still large variations between different designs., (Published by Elsevier Inc.)

The purpose of this study was to reveal the correlation between anteromedial (AM) and posterolateral (PL) femoral tunnel lengths in anatomical double-bundle anterior cruciate ligament (ACL) reconstruction and body size and knee morphology. Thirty-four subjects undergoing anatomical double-bundle ACL reconstruction were included in this study. Preoperative body size (height, body weight, and body mass index) was measured. Using preoperative magnetic resonance imaging (MRI), quadriceps tendon thickness and the whole anterior-posterior length of the knee were measured. Using postoperative computed tomography (CT), axial and sagittal views of the femoral condyle were evaluated. The correlation between measured intraoperative AM and PL femoral tunnel lengths, and body size and knee morphology using preoperative MRI and postoperative CT parameters was statistically analyzed. Both AM and PL femoral tunnel lengths were significantly correlated with height, body weight, posterior condylar length, and Blumensaat's line length. These results suggest that the femoral ACL tunnel length created using a transportal technique can be estimated preoperatively by measuring the subject's body size and/or the knee morphology using MRI or CT. For clinical relevance, surgeons should be careful to create femoral tunnel of sufficient length when using a transportal technique, especially in knees of subjects with smaller body size and knee morphology. Level of evidence is III., Competing Interests: None declared., (Thieme. All rights reserved.)

Kinematic tracking of native anatomy from stereo-radiography provides a quantitative basis for evaluating human movement. Conventional tracking procedures require significant manual effort and call for acquisition and annotation of subject-specific volumetric medical images. The current work introduces a framework for fully automatic tracking of native knee anatomy from dynamic stereo-radiography which forgoes reliance on volumetric scans. The method consists of three computational steps. First, captured radiographs are annotated with segmentation maps and anatomic landmarks using a convolutional neural network. Next, a non-convex polynomial optimization problem formulated from annotated landmarks is solved to acquire preliminary anatomy and pose estimates. Finally, a global optimization routine is performed for concurrent refinement of anatomy and pose. An objective function is maximized which quantifies similarities between masked radiographs and digitally reconstructed radiographs produced from statistical shape and intensity models. The proposed framework was evaluated against manually tracked trials comprising dynamic activities, and additional frames capturing a static knee phantom. Experiments revealed anatomic surface errors routinely below 1.0 mm in both evaluation cohorts. Median absolute errors of individual bone pose estimates were below 1.0 ∘ or mm for 15 out of 18 degrees of freedom in both evaluation cohorts. Results indicate that accurate pose estimation of native anatomy from stereo-radiography may be performed with significantly reduced manual effort, and without reliance on volumetric scans., (© 2024. The Author(s) under exclusive licence to Biomedical Engineering Society.)

Purpose: To analyse the reliability of ultrasound-guided measurement of the cartilage thickness at the medial femoral condyle in athletically active children and adolescents before and after mechanical load in relation to age, sex and type of sport., Methods: Three successive measurements were performed in 157 participants (median/min-max age: 13.1/6.0-18.0 years, 106 males) before and after mechanical load by squats at the same site of the medial femoral condyle by defined transducer positioning. Test-retest reliability was examined using Cronbach's α $\alpha $ calculation. Differences in cartilage thickness were analysed with respect to age, sex and type of practiced sports, respectively., Results: Excellent reliability was achieved both before and after mechanical load by 30 squats with a median cartilage thickness of 1.9 mm (range: 0.5-4.8 mm) before and 1.9 mm (0.4-4.6 mm) after mechanical load. Male cartilages were thicker (p < 0.01) before (median: 2.0 mm) and after (2.0 mm) load when compared to female cartilage (before: 1.6 mm; after: 1.7 mm). Median cartilage thickness was about three times higher in karate athletes (before: 2.3 mm; after: 2.4 mm) than in sports shooters (0.7; 0.7 mm). Cartilage thickness in track and field athletes, handball players and soccer players were found to lay in-between. Sport type related thickness changes after mechanical load were not significant., Conclusion: Medial femoral condyle cartilage thickness in childhood correlates with age, sex and practiced type of sports. Ultrasound is a reliable and simple, pain-free approach to evaluate the cartilage thickness in children and adolescents., Level of Evidence: Level III., (© 2024 The Authors. Knee Surgery, Sports Traumatology, Arthroscopy published by John Wiley & Sons Ltd on behalf of European Society of Sports Traumatology, Knee Surgery and Arthroscopy.)

Background: The intercondylar notch (ICN) is an important element of knee morphometry, in close relation to the anterior cruciate ligament (ACL). To find the average are of the anterior notch in each ICN specific shape (A-, W-, or U-shape). Methods: Magnetic resonance imaging (MRI) scans were independently analyzed by two experts, one orthopedic surgeon and one imaging physician. In all cases, the following measurements were done according to the existing definitions: ICN type, aICN area. Results: 65 cases (A-35.4%, W-26.2%, U-38,5%) were included in study; A and W notch types have smaller aICN areas, while U-type notch has bigger aICN area. Conclusion: The anterior intercondylar notch area varies significantly for each specific shape (A-, W, or U-shape), and does not corelates with height. This needs to be considered during ACL reconstruction, when choosing graft size., (Celsius.)

Finite element studies of the tibiofemoral joint have increased use in research, with attention often placed on the material models. Few studies assess the effect of meniscus modelling assumptions in image-based models on contact mechanics outcomes. This work aimed to assess the effect of modelling assumptions of the meniscus on knee contact mechanics and meniscus kinematics. A sensitivity analysis was performed using three specimen-specific tibiofemoral models and one generic knee model. The assumptions in representing the meniscus attachment on the tibia (shape of the roots and position of the attachment), the material properties of the meniscus, the shape of the meniscus and the alignment of the joint were evaluated, creating 40 model instances. The values of material parameters for the meniscus and the position of the root attachment had a small influence on the total contact area but not on the meniscus displacement or the force balance between condyles. Using 3D shapes to represent the roots instead of springs had a large influence in meniscus displacement but not in knee contact area. Changes in meniscus shape and in knee alignment had a significantly larger influence on all outcomes of interest, with differences two to six times larger than those due to material properties. The sensitivity study demonstrated the importance of meniscus shape and knee alignment on meniscus kinematics and knee contact mechanics, both being more important than the material properties or the position of the roots. It also showed that differences between knees were large, suggesting that clinical interpretations of modelling studies using single geometries should be avoided., (© 2024. The Author(s).)

Aim: To evaluate whether deep learning reconstruction (DLR) can accelerate the acquisition of magnetic resonance imaging (MRI) sequences of the knee for clinical use., Materials and Methods: Using a 1.5-T MRI scanner, sagittal fat-suppressed T2-weighted imaging (fs-T2WI), coronal proton density-weighted imaging (PDWI), and coronal T1-weighted imaging (T1WI) were performed. DLR was applied to images with a number of signal averages (NSA) of 1 to obtain 1DLR images. Then 1NSA, 1DLR, and 4NSA images were compared subjectively, and by noise (standard deviation of intra-articular water or medial meniscus) and contrast-to-noise ratio between two anatomical structures or between an anatomical structure and intra-articular water., Results: Twenty-seven healthy volunteers (age: 40.6 ± 11.9 years) were enrolled. Three 1DLR image sequences were obtained within 200 s (approximately 12 minutes for 4NSA image). According to objective evaluations, PDWI 1DLR images showed the smallest noise and significantly higher contrast than 1NSA and 4NSA images. For fs-T2WI, smaller noise and higher contrast were observed in the order of 4NSA, 1DLR, and 1NSA images. According to the subjective analysis, structure visibility, image noise, and overall image quality were significantly better for PDWI 1DLR than 1NSA images; moreover, the visibility of the meniscus and bone, image noise, and overall image quality were significantly better for 1DLR than 4NSA images. Fs-T2WI and T1WI 1DLR images showed no difference between 1DLR and 4NSA images., Conclusion: Compared to PDWI 4NSA images, PDWI 1DLR images were of higher quality, while the quality of fs-T2WI and T1WI 1DLR images was similar to that of 4NSA images., (Copyright © 2024 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.)

Background and Objectives: Bone age determination is a valuable method for forensic and disaster identifications of unknown human remains, as well as for medical and surgical procedural purposes. This retrospective research study aimed to determine the age based on epiphyseal fusion stages and investigate differences related to gender. Materials and Methods: X-rays of the knee were collected from medical imaging centers in hospitals in the south of Jordan and examined by two observers who determined the bone epiphyseal phase of closure for the femur, tibia, and fibula bone ends close to the knee based on a three-stage classification. Results: The main results revealed that females showed earlier epiphyseal union (Stage II) at the lower end of the femur and the upper ends of the tibia and fibula compared to males. In males, the start of complete union (Stage III) at knee bones was seen at the age of 17-18 years, while in females, it was seen at the age of 16-17 years. Additionally, knee bones showed complete union in 100% of males and females in the age groups 21-22 years and 20-21 years, respectively. Although females showed an earlier start and end of epiphyseal complete union than males, analysis of collected data showed no significant age differences between males and females at the three stages of epiphyseal union of the knee bones. Conclusions: Findings of the radiographic analysis of bone epiphyseal fusion at the knee joint are a helpful method for chronological age determination. This study supports the gender and ethnicity variation among different geographical locations. Studies with a high sample number would be needed to validate our findings.

This paper is the second in a two-part series that charts the evolution of appendicular musculature along the mammalian stem lineage, drawing upon the exceptional fossil record of extinct synapsids. Here, attention is focused on muscles of the hindlimb. Although the hindlimb skeleton did not undergo as marked a transformation on the line to mammals as did the forelimb skeleton, the anatomy of extant tetrapods indicates that major changes to musculature have nonetheless occurred. To better understand these changes, this study surveyed the osteological evidence for muscular attachments in extinct mammalian and nonmammalian synapsids, two extinct amniote outgroups, and a large selection of extant mammals, saurians, and salamanders. Observations were integrated into an explicit phylogenetic framework, comprising 80 character-state complexes covering all muscles crossing the hip, knee, and ankle joints. These were coded for 33 operational taxonomic units spanning >330 Ma of tetrapod evolution, and ancestral state reconstruction was used to evaluate the sequence of muscular evolution along the stem lineage from Amniota to Theria. The evolutionary history of mammalian hindlimb musculature was complex, nonlinear, and protracted, with several instances of convergence and pulses of anatomical transformation that continued well into the crown group. Numerous traits typically regarded as characteristically "mammalian" have much greater antiquity than previously recognized, and for some traits, most synapsids are probably more reflective of the ancestral amniote condition than are extant saurians. More broadly, this study highlights the utility of the fossil record in interpreting the evolutionary appearance of distinctive anatomies., (© 2023 American Association for Anatomy.)

Objectives: This study aimed to explore the use of Gerdy's tubercle (GT) as an innovative and dependable anatomical landmark for the proximal tibial cut in total knee arthroplasty (TKA) in cases with extensive knee degeneration., Materials and Methods: One hundred dry tibia bones and 10 formalin-fixed cadaveric knee specimens of both sexes were examined. A Zimmer NexGen tibial cutting guide and a Mitutoyo digital caliper were utilized to align the guide with the tibia's mechanical axis. The procedure was replicated on cadaver knees using a standardized medial parapatellar arthrotomy approach. Measurements included the distance from GT superior border to the resection line and the length of the tibia. A radiological study involving magnetic resonance imaging examinations of 48 patients, which were evaluated focusing on the upper border of GT and the least degenerated segment of the posterolateral part of the lateral tibial condyle, was conducted., Results: Anatomical measurements of GT and proximal tibial areas in 110 specimens showed slight but consistent variations with cadaver measurements. Magnetic resonance imaging analysis of 48 patients revealed notable sex differences in the distance between the superior border of GT and the tibia's posterolateral surface. There was also a significant negative correlation between the distance from GT to the posterolateral corner and cartilage thickness., Conclusion: Proper alignment in TKA is crucial for success, but identifying an extra-articular landmark for horizontal tibial resection remains challenging, particularly in severely arthritic knees. This study introduces GT as a novel anatomical landmark for TKA, offering a more reliable reference for achieving desired joint levels in knees with significant degenerative changes.

Objective: The study aims to evaluate the accuracy of an MRI-based artificial intelligence (AI) segmentation cartilage model by comparing it to the natural tibial plateau cartilage., Methods: This study included 33 patients (41 knees) with severe knee osteoarthritis scheduled to undergo total knee arthroplasty (TKA). All patients had a thin-section MRI before TKA. Our study is mainly divided into two parts: (i) In order to evaluate the MRI-based AI segmentation cartilage model's 2D accuracy, the natural tibial plateau was used as gold standard. The MRI-based AI segmentation cartilage model and the natural tibial plateau were represented in binary visualization (black and white) simulated photographed images by the application of Simulation Photography Technology. Both simulated photographed images were compared to evaluate the 2D Dice similarity coefficients (DSC). (ii) In order to evaluate the MRI-based AI segmentation cartilage model's 3D accuracy. Hand-crafted cartilage model based on knee CT was established. We used these hand-crafted CT-based knee cartilage model as gold standard to evaluate 2D and 3D consistency of between the MRI-based AI segmentation cartilage model and hand-crafted CT-based cartilage model. 3D registration technology was used for both models. Correlations between the MRI-based AI knee cartilage model and CT-based knee cartilage model were also assessed with the Pearson correlation coefficient., Results: The AI segmentation cartilage model produced reasonably high two-dimensional DSC. The average 2D DSC between MRI-based AI cartilage model and the tibial plateau cartilage is 0.83. The average 2D DSC between the AI segmentation cartilage model and the CT-based cartilage model is 0.82. As for 3D consistency, the average 3D DSC between MRI-based AI cartilage model and CT-based cartilage model is 0.52. However, the quantification of cartilage segmentation with the AI and CT-based models showed excellent correlation (r = 0.725; P values < 0.05)., Conclusion: Our study demonstrated that our MRI-based AI cartilage model can reliably extract morphologic features such as cartilage shape and defect location of the tibial plateau cartilage. This approach could potentially benefit clinical practices such as diagnosing osteoarthritis. However, in terms of cartilage thickness and three-dimensional accuracy, MRI-based AI cartilage model underestimate the actual cartilage volume. The previous AI verification methods may not be completely accurate and should be verified with natural cartilage images. Combining multiple verification methods will improve the accuracy of the AI model., (© 2024. The Author(s).)

Background: The goal was to determine the thickness and width of the knee joint meniscus at their different regions. The objective was to compare the dimensions at these regions and over the right- and left-sided specimens., Methods: The present study included 50 adult cadaveric knee joints, and 100 menisci (50 medial menisci and 50 lateral menisci) were studied. The meniscus was distributed into anterior, middle and posterior parts. Thickness and width at the mid-point of these three parts were determined by using the Vernier caliper., Results: The breadth of the medial meniscus was 8.38 ± 1.64 mm, 7.68 ± 1.92 mm and 13.93 ± 2.69 mm at the anterior, middle and posterior one-third regions. Same measurements for the lateral menisci at these regions were 9.84 ± 1.78 mm, 8.82 ± 2.01 mm and 10.18 ± 2.23 mm, respectively. The thickness of the medial meniscus was 4.49 ± 0.78 mm, 4.07 ± 0.81 mm and 4.79 ± 0.93 mm at these regions. The lateral meniscus thickness was 3.82 ± 0.69 mm, 4.43 ± 0.98 mm and 4.36 ± 0.8 mm, respectively., Conclusion: It is believed that this data is enlightening to the arthroscopic surgeon during the meniscus transplantation either by using synthetic material or allograft as the proper sizing of the meniscus is important to prevent complications due to inaccurate sizing., Competing Interests: No competing interests were disclosed., (Copyright: © 2024 Murlimanju BV et al.)

Purpose: Only a few reports have been published so far on factors that predict postoperative coronal alignment after unicompartmental knee arthroplasty (UKA). The purpose of this study is to clarify the relationship between the arithmetic hip-knee-ankle angle (aHKA) and postoperative coronal alignment after medial fixed-bearing UKA., Methods: One hundred and one consecutive patients (125 knees) who underwent medial fixed-bearing UKA were assessed. Pre- and postoperative coronal HKA angles, lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), and the thickness of the tibial and femoral bone cut were measured. aHKA was calculated as 180° - LDFA + MPTA. Correlations between postoperative HKA angle and aHKA, LDFA, and MPTA were investigated by single regression analysis. After the patients were divided into three groups according to the postoperative HKA angle, i.e., HKA angle > 180°, 175° < HKA angle ≤ 180°, and HKA angle ≤ 175°, aHKA, LDFA, MPTA, preoperative HKA angle, and the thickness of the distal femoral as well as tibial bone cut were compared among the three groups., Results: aHKA and MPTA were positively correlated with postoperative HKA angle, while no correlation was found between postoperative HKA angle and LDFA. Among the three groups classified by postoperative HKA angle, significant differences were found in aHKA, MPTA, and preoperative HKA angle, while no significant difference was found in LDFA and the amount of distal femoral and tibial osteotomies., Conclusions: aHKA was correlated with postoperative HKA angle after medial fixed-bearing UKA, which was probably due to the influence of MPTA., (© 2023. The Author(s).)

Purpose: To study the morphology and the morphometry of the oblique popliteal ligament (OPL)., Methods: Thirty cadaver knees were dissected to study the morphology and morphometry of the OPL. For the measurement of the morphology of the OPL a standard tape and the vernier callipers were used., Result: Out of 30 specimens 14 were Y shaped, 10 were band shaped, and 6 were Z shaped observed. Total length was measured on both the limbs, on the right side it was 4.5 ± 0.4 cm and on the left side 4.5 ± 0.5 cm was recorded. Width at the medial attachment was also measured on both the limbs, on the right side it was 4.6 ± 0.5 cm and on the left side 4.7 ± 0.5 cm was recorded. And width at the lateral attachment was recorded too, on the right side it was 4 ± 0.3 cm and on the left side it was 4 ± 0.3 cm. Width at the midpoint was recorded as on the right side 3.5 ± 0.2 cm and on the left side 3.5 ± 0.2 cm., Conclusion: The OPL is a thick ligament that arises as an extension of the semimembranosus, and it exists in various morphology which includes band, Y, Z, complex shapes., (© 2024. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

The suprapatellar fat pad is an adipose tissue located in the anterior knee whose role in osteoarthritis is still debated. Considering that anatomy drives function, the aim of this histotopographic study was to investigate the specific morphological features of the suprapatellar fat pad versus the infrapatellar fat pad in the absence of osteoarthritis, for a broad comparative analysis. Suprapatellar fat pad and infrapatellar fat pad tissue samples (n = 10/group) underwent microscopical/immunohistochemical staining and transmission electron microscopy analysis; thus, tissue-specific characteristics (i.e., vessels and nerve endings presence, lobuli, adipocytes features, septa), including extracellular matrix proteins prevalence (collagens, elastic fibers), were focused. Multiphoton microscopy was also adopted to evaluate collagen fiber orientation within the samples by Fast Fourier Transform (coherency calculation). The absence of inflammation was confirmed, and comparable counted vessels and nerve endings were shown. Like the infrapatellar fat pad, the suprapatellar fat pad appeared as a white adipose tissue with lobuli and septa of comparable diameter and thickness, respectively. Tissue main characteristics were also proved by both semithin sections and transmission electron microscopy analysis. The suprapatellar fat pad adipocytes were roundish and with a smaller area, perimeter, and major axis than that of the infrapatellar fat pad. The collagen fibers surrounding them showed no significant difference in collagen type I and significantly higher values for collagen type III in the infrapatellar fat pad group. Regarding the septa, elastic fiber content was statistically comparable between the two groups, even though more represented by the suprapatellar fat pad. Total collagen was significantly higher in the infrapatellar fat pad and comparing collagen type I and type III they were similarly represented in the whole cohort despite collagen type I appearing to be higher in the infrapatellar fat pad than in the suprapatellar fat pad and vice versa for collagen type III. Second harmonic generation microscopy confirmed through coherency calculation an anisotropic distribution of septa collagen fibers. From a mechanical point of view, the different morphological characteristics determined a major stiffness for the infrapatellar fat pad with respect to the suprapatellar fat pad. This study provides, for the first time, a topographic description of the suprapatellar fat pad compared to the infrapatellar fat pad; differences between the two groups may be attributed to a different anatomical location within the knee; the results gathered here may be useful for a more complete interpretation of osteoarthritis disease, involving not only cartilage but the whole joint., (© 2023 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.)

Mechanical alignment (MA) and its tenets have been considered essential for total knee arthroplasty (TKA) success since they were introduced in 1973. However, over time, there have been colossal advances in our knowledge and understanding of the anatomy and kinematics of the knee, as well as in surgical precision and implants. However, the MA systematic principles of prosthetic arthroplasty and implant position related to the lower-extremity mechanical axis, have only recently been called into question. The high rates of dissatisfaction and residual pain reported after MA TKA prompted this questioning, and that leaves plenty of room for improvement. Despite the general consensus that there is great variability between patients' anatomy, it is still the norm to carry out a systematic operation that does not consider individual variations. Evolving to a more personalized arthroplasty surgery was proposed as a rational and reasonable option to improve patient outcomes. Transitioning to a personalized TKA approach requires questioning and even disregarding certain MA TKA principles. Based on current knowledge, we can state that certain principles are erroneous or unfounded. The aim of this narrative review was to discuss and challenge 10 previously accepted, yet we believe, flawed, principles of MA, and to present an alternative concept, which is rooted in personalized TKA techniques., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Purpose: The anterior flange height of the current femoral component increases with an increasing distal femoral anteroposterior dimension. During total knee arthroplasty (TKA), we have observed that a large femur may have a thinner anterior condyle, whereas a small femur may have a thicker anterior condyle. The first purpose of this study was to examine whether the femoral anterior condyle height decreases as the distal femoral anteroposterior size increases and whether gender differences exist in anterior condyle height., Methods: A total of 1218 knees undergoing TKA intraoperative and computed tomography scans from 303 healthy knees were used to measure the anterior lateral condylar height (ALCH), anterior medial condylar height (AMCH), and the lateral anteroposterior (LAP) and medial anteroposterior (MAP) dimensions of distal femurs. The LAP and MAP measurements were used for adjustments to determine whether gender differences exist in anterior condyle heights. Linear regression analysis was performed to determine correlations between ALCH and LAP or between AMCH and MAP., Results: There were significant differences between males and females in ALCH in both the CT and TKA groups and AMCH in the CT group (all P<0.01). After adjusting for LAP and MAP, there were significant gender differences in the lateral and medial condylar heights in both groups (P<0.01). There were significant negative correlations between ALCH and LAP values and between AMCH and MAP values in both CT and TKA measurements, with the LAP and MAP values increasing as ALCH and AMCH decreased., Conclusions: The results demonstrate that femoral anterior condylar height decreased with increasing anteroposterior dimension in both the medial and lateral condyle. In addition, this study also showed that anterior condylar heights are highly variable, with gender differences. The data may provide an important reference for designing femoral anterior flange thickness to precisely match the natural anterior condylar anatomy., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Yang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Objectives: This study aims to evaluate the inter-observer reliability of fibula-condyle-patella angle measurements and to compare it with other measurement techniques., Patients and Methods: Between January 01, 2023 and January 31, 2023, a total of 108 patients (20 males, 88 females; mean age: 47.5±12.0 years; range, 18 to 72 years) who underwent X-rays using the fibula-condyle-patella angle, Insall-Salvati, Caton-Deschamps, Blackburne-Pell, and plateau-patella angle (PPA) methods were retrospectively analyzed. Knee lateral radiographs taken in at least 30 degrees of flexion and appropriate rotation were scanned. All measurements were made by two orthopedic surgeons who were blinded to measurement methods., Results: Right knee patellar height measurements were conducted in 56 patients, while left knee patellar heights were assessed in 52 patients. The highest inter-observer concordance was found in the fibula-condyle-patella angle. The second highest concordance was found in the Insall-Salvati. The highest concordance correlation was found with PPA in the measurements of both researchers., Conclusion: The fibula-condyle-patella angle is a reliable technique with a good inter-observer reliability for measuring patellar height. We believe that this study will inspire future research to establish comprehensive reference values for clinical applications.

Purpose: Patient-specific alignment (PSA) technique tries to achieve balanced gaps and simultaneously rebuild the individual bony phenotype. The hypothesis was: PSA technique achieves balanced knees in a high percentage with more anatomical resections than adjusted mechanical alignment (AMA)., Methods: Three hundred sixty-seven patients underwent navigated total knee arthroplasty (TKA) with a tibia-first gap-balanced PSA technique. Resection boundaries for medial proximal tibia angle (MPTA) of 86-92°, mechanical lateral distal femoral angle (mLDFA) of 86-92°, and hip-knee-ankle angle (HKA) of 175-185° were defined. Preoperative and intraoperative parameters of HKA, MPTA, mLDFA, and gap widths were recorded. Depending on the coronal deformity, the patients were divided into three groups: varus HKA < 178°; straight 178-182° and valgus HKA > 182°. The stability was analysed by assessing the difference between medial and lateral extension and flexion gaps as well as between flexion and extension gaps. All PSA measurements were compared with data from a previously published AMA series., Results: PSA achieved balanced gaps in extension, flexion and between flexion/extension in over 90% of cases, being similar to AMA. In PSA, MPTA and mLDFA were restored within 1°, except in extreme varus (MPTA difference 2°) and valgus knees (mLDFA difference 3°). This was caused by the defined boundaries of the alignment technique. This individualised reconstruction led to significantly more anatomical resections of all tibia and femur resections., Conclusion: A tibia-first, gap-balanced PSA technique achieves balanced joints in more than 90% of cases. By maintaining preoperative MPTA and mLDFA to a high extent, far more anatomical resections, compared to AMA were performed. Future studies need to be conducted to investigate whether those promising intraoperative results correlate with postoperative patient outcomes and whether patients outside the 5° corridor have higher failure rates., Level of Evidence: Level III, retrospective cohort study., (© 2024 European Society of Sports Traumatology, Knee Surgery and Arthroscopy.)

Purpose: To determine the effect of saucerization surgery on knee joint morphology associated with a complete discoid lateral meniscus (DLM) using magnetic resonance (MR) imaging., Methods: This retrospective study included cases had undergone saucerization surgery for symptomatic DLM between 2007 and 2022. All cases were divided into two by age group: < 12 (U13) and > 13 (O13). The cases in the match group were randomly selected from preoperative cases in the O13 group matched with the age at the final follow-up (F/U) of cases in the U13 group. The following morphological parameters were evaluated using MR images preoperatively and at the final postoperative F/U in each group: anterior obliquity of the lateral tibial plateau (AOLTP), posterior obliquity of the lateral tibial plateau (POLTP), and the lowest point of the lateral femoral condyle (LPLFC). Each parameter was compared between the U13 preoperative (pre-OP) group and the O13 pre-OP group, the preoperative and final follow-up in the U13, and the U13 group at the final F/U and the match group preoperatively., Results: A total of 77 cases were evaluated. 31 cases were in the U13 pre-OP group and 46 were in the O13 pre-OP group. With a minimal F/U of 2 years, 27 cases in the U13 group and 36 in the O13 group were included. The mean F/U period was 4.6 years in the U13 group and 3.2 years in the O13 group. 32 cases were included in the match group. In the match group, the inclination of the POLTP was significantly larger (P = 0.042) and the LPLFC was more lateral (P = 0.0034) than at the final F/U in the U13 group., Conclusions: Saucerization surgery for DLM in juvenile patients can prevent progression to the characteristic bone morphology DLM. These results could help the surgeon making the decision when the surgery would be performed for symptomatic DLM patients., Level of Evidence: Retrospective comparative study; level of evidence, 3., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background Anatomic variations have been implicated as one of the intrinsic causes of injuries to the cruciate ligaments which can induce a functional deficiency to the knee. Narrow cruciate ligament widths as well as narrow femoral intercondylar notch widths can increase the risk of these ligaments rupturing. Objective To correlate the width of the femoral intercondylar notch (ICN) with anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) widths on MRI of the knee joint. Method A total of 46 patients who met the inclusion criteria were evaluated. Intercondylar notch was identified on coronal T1W images while anterior cruciate ligament and posterior cruciate ligament were identified on proton density coronal images. All the widths were measured in the same plane at a mid-coronal level where anterior cruciate ligament and posterior cruciate ligament cross each other. Result Our result showed a significant correlation between the widths of intercondylar notch and anterior cruciate ligament (r = 0.68, p < 0.001) and between intercondylar notch width (INW) and posterior cruciate ligament width (r = 0.65, p < 0.001). Overall, the mean intercondylar notch width measured was 17.5 ±2.5 mm (range 11.8 to 21.8 mm), the mean anterior cruciate ligament width was 5.9 ±1.3 mm (range 3.3 to 8.6 mm), and the mean posterior cruciate ligament width was 8.9 ±1.5 mm (range 5.9 to 11.8 mm). A statistically significant difference was observed between males and females for mean widths of intercondylar notch (p < 0.001) and posterior cruciate ligament (p=0.01). However, no statistically significant difference was seen for anterior cruciate ligament width (p=0.07) between the two genders. Conclusion Measurement of the femoral intercondylar notch width can be used as an indicator of anterior cruciate ligament and posterior cruciate ligament widths which can further assist to identify the individuals who are more susceptible to cruciate ligament injuries.

The knee joint capsules composed of a fibrous layer and a synovial layer. The knee meniscus consists of the superficial network, lamellar layer, tie fibre and circumferential bundles. However, the continuous structure of the knee joint capsule and meniscus has not been reported. Fetal and adult pigs were used to investigate the structural relationship between the stifle joint capsule and meniscus based on the gross anatomy and histological findings. In the gross anatomical examination, the joint capsule appeared to have separated attachments to the meniscus, except for the lower aspect of the popliteal hiatus. Histologically, the lower half of the popliteal hiatus was found to have separated attachments, with vessels running between the attachments of the joint capsules. The synovial layer of the joint capsule continued to the superficial network, and the fibrous layer of the joint capsule continued to the lamellar layer and tie fibres. There were two routes of arterial entry into the meniscus: intracapsular and intercapsular. It appeared that the presence of separated attachments of the joint capsule was necessary to allow the intercapsular route. This study clarified for the first time the routes of feeding vessels entering the meniscus and proposed to call this entry point the meniscus hilum. We consider that this detailed anatomical information is important for understanding the continuation between the joint capsule and the meniscus., (© 2023 The Authors. Anatomia, Histologia, Embryologia published by Wiley-VCH GmbH.)

Ligamentum Mucosum(LM) is a ligamentous structure within the synovial layer of the knee joint capsule. For a long time LM was perceived as the vestigial remnant from the embryological development of the knee. Being treated as an irrelevant structure LM was often the first victim of shaver during arthroscopy. However, last years have shown increased interest in this structure due to its potentially significant clinical role. Our aim was to classify LM based on its morphological characteristics and examine its microanatomy using immunohistochemical analysis to reveal the potential clinical value for surgeons. We have examined sixteen fresh frozen lower limbs, 6 females (mean age 83.1 ± 3.4 years) and 10 males (mean age 84.2 ± 6.8 years). Classical histological H+E stain was routinely conducted. Subsequently, CD31 antibody (DAKO, Monoclonal Mouse Anti-Human, Clone JC70A) was used to mark vascular epithelium. Monoclonal Mouse Anti-Human Neurofilament Protein (NFP) antibody (DAKO, Clone 2F11) was used to expose the nerves. Moreover, we have conducted arthroscopic visualizing and suturing LM to the torn ACL during routinely performed arthroscopic suturing of the ACL. The dissection process has revealed that LM was present only in 75% of cases. Histological examination confirmed the presence of longitudinal collagen fiber bundles in all samples. Tiny nerves were confirmed by NFP, along the subsynovial layer in all samples. CD-31 immunostain revealed the presence of many vascular vessels along the entire ligament, especially well developed at its distal end. Our study has revealed that LM contains rich vascular network. Thus, it may be a donor for the revascularization process after ACL tear or reconstruction which may improve the recovery. Another great advantage of the LM is the presence of nerves along the subsynovial layer, hopefully they may serve as the source of reinnervation and hence better clinical outcome. Based on our results we believe that seemingly irrelevant LM may be very useful during surgical procedures in the knee region. Suturing LM to the ACL may not only prevent the infrapatellar fat pad from subluxation but also improve the blood flow and reinnervation of the injured ACL. Until now there are only a few studies examining microanatomy of the LM. This basic knowledge may serve as the foundation for surgical procedures. Hopefully our findings may be useful for surgeons while planning surgical procedures or clinicians while diagnosing patients who suffer anterior knee pain., Competing Interests: Declaration of Competing Interest The authors declare that they have no competing interests., (Copyright © 2023 Elsevier GmbH. All rights reserved.)

Medial meniscal extrusion (MME) is a structural abnormality that leads to early knee osteoarthritis; however, its formation remains debated. For anatomical consideration of the mechanism underlying MME formation, we examined the capsular attachment on the posteromedial tibia and its layered association with the semimembranosus. Fourteen knees of eight body donors were analyzed in this study; six knees were grouped for macroscopic analysis, whereas four knees each were grouped for histological and phosphotungstic acid-enhanced micro-computed tomography analyses. The capsular attachment varied in width according to location and was not distant from the articular cartilage and posterior root. A portion of the posteromedial joint capsule formed the semimembranosus tendinous sheath. The dense fibrous membrane superficial to the semimembranosus, which was continuous from its tendinous sheath, existed as one of the layers of the joint capsule. The aforementioned findings were confirmed in all specimens. Based on the capsular attachment and its layered association with the semimembranosus, the conventional posteromedial knee ligaments may be only a part of the joint capsule divided into two layers by the semimembranosus. If the coordinated action of the joint capsule and semimembranosus partially contributes to the medial meniscus stability, such a structural problem may affect MME formation., (© 2023. The Author(s).)

Anterior cruciate ligament (ACL) injuries commonly lead to translational and rotational tibiofemoral instability. The morphology of the medial tibial eminence (MTE) has received increased attention regarding its role in tibiofemoral stability in ACL-injured knees. Therefore, quantification of MTE dimensions on clinical imaging may help clinicians predict knee stability after ACL injury. Although magnetic resonance imaging (MRI) is routinely obtained in patients with ACL injuries, whether the dimensions of the MTE can be accurate quantified on MRI is unknown. The purpose of this study was to assess the degree of correlation between measurements of MTE height and width on computed tomography (CT) versus MRI. An institutional picture archiving and communication system imaging database was used to identify patients aged between 15 and 60 years who received concurrent MRI and CT of the same knee within a 1-year interval. Knees with significant arthrosis, deformity, intraarticular fracture, or hardware-related artifact that obscured visualization of the MTE were excluded. Mean differences and interstudy agreement between CT and MRI MTE measurements were compared using concordance correlation coefficient ( r c ) and Bland-Altman analysis. A total of 41 knees in 38 patients (mean age, 37 years; 82% male) were analyzed. Interrater reliability for CT and MRI measurements was high (intraclass correlation coefficient = 0.740-0.954). On coronal CT and MRI, mean MTE height measurements were 10.4 ± 1.9 and 10.4 ± 1.8 mm, respectively; mean MTE width measurements were 14.6 ± 3.6 and 14.2 ± 3.0 mm, respectively. On sagittal CT and MRI, mean MTE height measurements were 11.6 ± 1.7 and 11.7 ± 1.7 mm, respectively; mean MTE width measurements were 36.5 ± 4.8 and 36.2 ± 5.0 mm, respectively. Good agreement was observed between CT and MRI measurements of MTE height and width on coronal and sagittal planes ( r c  = 0.947-0.969). Measurements of MTE height and width were similar on MRI relative to CT on both coronal and sagittal planes. MRI may be suitable for characterizing the dimensions of the MTE when clinically evaluating patients with ACL injuries, potentially allowing for individualized patient care., Competing Interests: None declared., (Thieme. All rights reserved.)

Objective: To review the research progress of injection sites of local infiltration analgesia (LIA) in total knee arthroplasty (TKA)., Methods: The relevant domestic and foreign literature in recent years was extensively reviewed. The neuroanatomy of the knee, and the research progress of the selection and the difference of effectiveness between different injection sites of LIA in clinical studies were summarized., Results: Large concentrations of nociceptors are present throughout the various tissues of the knee joint. Patellar tendon, subpatellar fat pad, lateral collateral ligament insertions, iliotibial band insertions, suprapatellar capsule, and posterior capsule were more sensitive to pain. Most current studies support injections into the lateral capsule, collateral ligament, retinaculum, quadriceps tendon, fat pad, and subcutaneous tissue. Whether to inject into the back of the knee and subperiosteum is controversial., Conclusion: The relative difference of knee tissue sensitivity to pain has guiding significance for the selection of LIA injection site after TKA. Although researchers have conducted clinical trials on injection site and technique of LIA in TKA, there are certain limitations. The optimal scheme has not been determined yet, and further studies are needed.

Purpose: The purpose of this systematic review and meta-analysis was to investigate the variability in tibial geometric ratios among knees of different sexes and races to determine whether commercially-available tibial baseplates accommodate the morphologic diversity. The hypothesis was that anthropometric studies report considerable variability of tibial geometric ratios among sexes and races., Methods: This systematic review and meta-analysis was performed according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) criteria. Two authors independently conducted an electronic search using MEDLINE ® and Embase ® on 28 January 2021 for clinical studies reporting on tibial geometric ratios. Tibial geometric ratios, as reported by the clinical studies, were represented by plotting their means and two standard deviations for comparison to two symmetric and two asymmetric commercially-available tibial baseplates., Results: A total of 27 articles that reported on a combined total of 20,944 knees were eligible for data extraction. Variation in tibial aspect ratios was equal among sexes. The greatest variation in aspect ratio was observed among East Asians, followed by Caucasians, African-Americans, Indian and Middle Easterns. The variation in tibial asymmetry ratio was larger among men compared to women. The greatest variation in asymmetry ratio was observed among African-Americans, followed by Caucasians, East Asians, Indian and Middle Easterns. Bone-implant mismatch of > 3 mm overhang or > 4 mm under-coverage with four commercially-available tibial baseplates occurred in large proportions of knees due to variations in aspect ratio (in 17-100% of knees) and asymmetry ratio (in 7-100% of knees)., Conclusion: Anthropometric studies reported considerable inter-individual variability of tibial geometric ratios, which exceeded effects of sexual dimorphism and racial diversity. Bone-implant mismatch may be unavoidable in a large proportion of knees, when considering that a surgeon generally only uses one or a few TKA brands. These findings support the drive towards patient-specific implants to potentially achieve accurate bone-implant fit by implant customisation., Level of Evidence: IV., (© 2021. European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Purpose: The aim of this study was to analyze and quantify the changes in native coronal alignment of a population of TKA patients according to different alignment goals., Methods: Five hundred and twenty TKAs were analyzed. The following angles were measured using an image-free navigation system prior to prosthetic implantation: medial femorotibial mechanical angle without stress and with maximum manual stress to reduce the deformity, medial distal femoral mechanical angle, medial proximal tibial mechanical angle. The native angles were derived from the osteoarthritic knee angles using a validated correction technique, and the overall, femoral and tibial coronal phenotypes were defined. Five different coronal alignment techniques were simulated: mechanical (MA), restricted mechanical (RMA), anatomical (AA), kinematic (KA) and restricted kinematic (RKA). The overall, femoral and tibial coronal phenotypes were compared before and after TKA. The primary endpoint was the binary criterion of whether or not TKA restored the natural overall phenotype. Secondary endpoints were the binary criteria of whether or not the natural femoral and tibial phenotypes were restored by TKA. The rates of restored and non restored phenotypes were compared with a Chi-square test at a 0.05 level of significance, with post hoc tests between all pairs of techniques at a 0.01 level of significance., Results: The overall phenotype was restored significantly differently by the five alignment techniques: 15% for MA, 23% for RMA, 2% for AA, 100% for KA and 79% for RKA (p < 0.001). There was a significant difference between each of the technique pairs (p < 0.01 to p < 0.001), except for the mechanical alignment-restricted mechanical alignment pair. The femoral phenotype was restored significantly differently by the five alignment techniques: 37% for MA, 58% for RMA, 19% for AA, 100% for KA and 85% for RKA (p < 0.001). The tibial phenotype was restored significantly differently by the five alignment techniques: 36% for MA, 36% for RMA, 17% for AA, 100% for KA and 88% for RKA (p < 0.001). There was a significant difference between each pair of techniques for both femoral and tibial phenotypes (p < 0.01 to p < 0.001)., Conclusion: Except for the kinematic alignment technique, the various alignment techniques induce significant changes in the pre-arthritic anatomy of the TKA patient. The surgeon must be aware of these modifications. The clinical relevance of this alteration still needs to be defined., Level of Evidence: III., (© 2022. The Author(s) under exclusive licence to European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA).)

Introduction: A discoid lateral meniscus (DLM) is associated with increased risk for meniscal tears and progression of knee joint osteoarthritis. Our aim was to differentiate knee joint morphology between patients with and without a DLM, as a function of skeletal maturity, using magnetic (MR) imaging., Materials and Methods: This was a retrospective analysis of MR images of the knee for 110 patients, 6-49 years of age. Of these, 62 were in the open physis group (38 with a DLM) and 48 in the closed physis group (23 with a DLM). The following morphological parameters were measured: anterior obliquity of the lateral tibial plateau (AOLTP), posterior obliquity of the lateral tibial plateau (POLTP), the lowest point of the lateral femoral condyle (LPLFC), and the posterior lateral condylar angle (PLCA)., Results: Regardless of skeletal maturity, a DLM was associated with a greater inclination of the POLTP, lateralization of the LPLFC, and smaller PLCA (p < 0.001 for all compared to that of the control group). In the DLM group, the inclination of the AOLTP and the POLTP were significantly smaller (p < 0.001) and the LPLFC was more lateral (p < 0.001) in the closed physis group than in the open physis group. In the control group, the inclination of the POLTP was larger (p < 0.001) and the PLCA smaller (p = 0.019) in the open than in the closed physis group., Conclusions: We identified a characteristic knee morphology among patients with a complete DLM using MR imaging, which was observed before physeal closure and persisted after skeletal maturity was attained. We also noted lateralization of the LPLFC in the presence of a DLM, with an increase in lateralization with skeletal maturation., Level of Evidence: Case-control study, III., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

This study aimed to investigate the relationship between body mass index (BMI), age, and sex and morphological risk factors that may cause internal knee injuries. The magnetic resonance images of 728 participants who met the inclusion criteria and had a mean age of 34.4 ± 6.8 years were analyzed retrospectively. Demographic differences were analyzed by measuring 17 morphological parameters known to be associated with internal knee injuries. Men had a higher anterior cruciate ligament length (ACLL), anterior cruciate ligament width, (ACLW) lateral femoral condylar width (LFCW), medial femoral condylar width (MFCW), lateral femoral condylar depth (LFCD), distal femoral width (DFW), and intercondylar femoral width (IFW) than women (P < .05). By contrast, the medial meniscus bone angle (MMBA) was lower in men than in women (P < .05). Women aged 31 to 40 years had a lower Insall-Salvati index (ISI) and lateral tibial posterior slope (LTPS) than those aged 21 to 30 years (P < .05), whereas men aged 31 to 40 years had a lower ISI than those aged 21 to 30 years (P < .05). Women with BMI ≥ 30 had a higher LFCW and MFCW but a lower ISI than those with BMI < 30 (P < .05). Men with BMI ≥ 30 had a higher LFCW, MFCW, DFW, and MMBA than those with BMI < 30 (P < .05). The use of value ranges structured according to demographic characteristics, rather than a single value range for all patient groups, may contribute to the evaluation and treatment of the morphological features that are thought to be effective in the development of internal knee injuries. These values may also shed light on future radiological risk scoring systems and artificial intelligence applications in medicine., Competing Interests: The authors have no funding and conflicts of interest to disclose., (Copyright © 2023 the Author(s). Published by Wolters Kluwer Health, Inc.)

The ligamentum mucosum (LM) is a ligamentous structure within the synovial layer of the knee joint capsule. For a long time LM was perceived as the vestigial remnant from the embryological development of the knee. However, last years have shown increased interest in this structure due to its potentially significant clinical role. Fifty-one, 12 females (mean age 83.1 ± 3.4 years) and 39 males (mean age 84.2 ± 6.8 years) fixed in 10% formalin were examined. Upon dissection, the following morphological features of the LM were assessed: the types of LM, morphometric measurement and histological analysis of each type. The LM was present in 66.7% of all examined specimens. Three different types were recognized: Type I (55.9%)-single band with attachment to the intercondylar notch, Type IIa-bifurcated ligament with attachment to the anterior cruciate ligament, Type IIb-bifurcated ligament with both attachments to the intercondylar notch, Type III-double ligament with two independent bands and attachments to the intercondylar notch and to the knee joint capsule. The LM is variable and probably evolutionary changes are the reason. In our study we propose the new clinically useful classification supported by its anatomical and histological characteristics. Type IIa seems to be the most important from the clinical point of view, as it may be responsible for clinical issues and should be paid attention while diagnosing patients suffering from anterior cruciate ligament torn or anterior knee pain., (© 2022 American Association of Clinical Anatomists and British Association of Clinical Anatomists.)

Detailed knowledge of anatomy helps to understand pathologic processes. This article focuses on the anatomy and functionality of the knee, with emphasis on recently studied concepts and anatomic features that have an association with the development of pathology. The most common anatomic variants posing a challenge for diagnosis and other common findings in asymptomatic patients are reviewed. Good understanding of the different surgical procedures helps in providing as much information as possible to guarantee a positive outcome, improving prognosis. We review what are the commonly expected postsurgical appearances and the most common postsurgical complications., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Objective: Total knee arthroplasty has been popular in recent years. Morphometry of proximal tibia is important for surgeons to perform successful total knee arthroplasty. Aim of this study was to reappraise the proximal tibia morphometry., Methods: In this study, 57 human dry tibia were evaluated. Anteroposterior and mediolateral dimensions of tibial condyles, maximum width of superior articular surface and length of tibia were measured. Furthermore, morphometric measurements of the intercondylar area and Gerdy's tubercle (infracondylar tibial tubercle) were done. All measurements were performed by two observers using a digital caliper., Results: Mean anteroposterior and mediolateral dimensions of medial tibial condyle were found 39.76 and 23.27 mm, respectively. Mean anteroposterior and mediolateral dimensions of lateral tibial condyle were measured 34.72 and 21.83 mm, respectively. Mean anteroposterior dimension of intercondylar area was 41.62 mm. Shape of the Gerdy's tubercle was oval in 76.8%, irregular in 12.5%, and triangular in 10.7%. Texture of the tubercle was smooth in 85.7% and rough in 14.3%. Mean superoinferior and mediolateral dimensions of Gerdy's tubercle were 12.28 and 10.27 mm, respectively. Anteroposterior and mediolateral dimensions of tibial condyles were significantly higher (p < 0.05) for the medial condyle. Positive and statistically significant correlations were found between the tibial length and the other parameters (p < 0.05, r > 0.40)., Conclusion: The morphometric data of tibial plateau are important for surgeons during total knee arthroplasty. The superoinferior and mediolateral dimensions of the Gerdy's tubercle, the distance between Gerdy's tubercle and tibial tuberosity, the distance between Gerdy's tubercle and lateral tibial plateau were measured for the first time in our study. The data obtained from this study can be used as a guideline in designing tibial component of the total knee prosthesis in Turkish population. In arthroplasty, patient-specific prosthetic implants may eradicate implant mismatch in the near future., (© 2023. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)