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Purpose: To analyze, quantify, and redefine the anatomy of the peripheral attachments of the lateral meniscal body to further understand how the structures might play a part in preventing meniscal extrusion and how it might be applied to surgical techniques., Methods: Ten nonpaired fresh-frozen cadaveric knees without prior injury, a surgical history, or gross anatomic abnormality were included. There were 5 right and 5 left knees, and 50% were from male donors and 50% were from female donors. All the dissections were performed by a group of 3 experts in knee surgery (2 knee surgeons and 1 anatomy professor who oversaw the design of the dissection protocol and guided this protocol). The main peripheral structures associated with the lateral meniscus body were dissected to determine the insertion, size, thickness, and location of the lateral meniscotibial ligament (LMTL), popliteofibular ligament (PFL), and popliteomeniscal ligament (PML). The distance to various landmarks in the lateral compartment was also determined using an electronic caliper. Moreover, a histopathologic study was carried out., Results: The average thickness of the LMTL was 0.62 ± 0.18 mm (95% confidence interval [CI], 0.49-0.75 mm); that of the PFL-PML area was 1.05 ± 0.27 mm (95% CI, 0.85-1.24 mm). The anteroposterior distance measured 15.80 ± 4.80 mm (95% CI, 12.40-19.30 mm) for the LMTL and 10.40 ± 1.70 mm (95% CI, 9.21-11.63 mm) for the PFL-PML area. The anteroposterior distance of the whole menisco-tibio-popliteus-fibular complex (MTPFC) was 28.20 ± 4.95 mm (95% CI, 24.70-31.70 mm). The average distance from the MTPFC to the posterior horn of the lateral meniscal root was 29.30 ± 2.29 mm (95% CI, 27.60-30.90 mm), whereas that to the anterior horn was 32.00 ± 4.80 mm (95% CI, 28.60-35.50 mm). The average distance from the tibial insertion of the LMTL to the articular surface was 5.59 ± 1.22 mm (95% CI, 4.72-6.46 mm). In all the anatomic components of the knee, a consistent morphologic and histologic pattern was observed between the fibers of the LMTL, PFL, and PML and those of the lateral meniscal body, making up the proposed MTPFC., Conclusions: A consistent anatomic pattern has been identified between the lateral meniscal body and the LMTL, PFL, and PML, forming an interconnected complex that would seem appropriate to denominate the MTPFC. A precise study of this region and appropriate nomenclature for it could contribute to a better understanding of the mechanism of lateral meniscal injuries at this level, as well as the development of surgical techniques to treat these lesions and prevent extrusion., Clinical Relevance: This study contributes to the understanding of the lateral meniscal body attachments and the functions they serve. This will lead to improvements in the treatment of lesions in this region, including the development of surgical techniques., (Copyright © 2020 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the effect of the location of the femoral tunnel on 3-dimensional (3D) computed tomography (CT) upon the postoperative tunnel widening after anterior cruciate ligament (ACL) reconstructions., Methods: Inclusion criteria were patients who underwent hamstring ACL reconstructions using an adjustable-loop cortical suspension device, underwent 3D CT at the day after surgery, and were followed for a minimum of 2 years after surgery. Exclusion criteria were patients with combined ligament injury and reinjury after reconstruction. Using 3D CT, the center of the femoral tunnel aperture was located on a standardized grid system. The center of the ACL footprint was defined from the literature. The femoral tunnel location was classified as anatomic if it located within 2 standard deviations of the center position. If it was outside the 2 standard deviations, the tunnel was classified as nonanatomic. The patients were divided into either anatomic or nonanatomic groups. Femoral tunnel angles on both sagittal and coronal planes were measured. Both femoral and tibial tunnels measured on anteroposterior and lateral radiographs at immediate postoperative day and at 2 years after surgery. Postoperative knee stability and patient-reported outcomes were evaluated., Results: There were 37 patients in anatomical group and 52 patients in nonanatomical group among enrolled 87 patients. There were no differences in demographics between the 2 groups. There were no differences in the femoral tunnel angles and postoperative tunnel widening between the 2 groups. A higher position correlated to the femoral tunnel widening at 2 years postoperatively. Postoperative knee stability and patient-reported outcomes showed no statistically significant differences between the 2 groups., Conclusions: There was no significant difference in postoperative tunnel widening or clinical outcomes between anatomic and nonanatomic femoral tunnel location after hamstring ACL reconstructions. A higher position correlated to the femoral tunnel widening at 2 years postoperatively., Level of Evidence: Level III, Retrospective comparative study., (Copyright © 2019 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Improved understanding of the anatomy and biomechanics of the posterior cruciate ligament (PCL) has led to the evolution and improvement of anatomic-based reconstructions. The PCL is composed of the larger anterolateral bundle (ALB) and the smaller posteromedial bundle (PMB). On the femoral side, the ALB spans from the trochlear point to the medial arch point on the roof of the notch, while the PMB occupies the medial wall from the medial arch point to the most posterior aspect of the articular cartilage. Because of these broad and distinct attachments, the bundles have a load-sharing, synergistic and codominant relationship. Both restrict posterior translation; however, the ALB has a proportionally larger role in restricting translation throughout flexion, whereas the PMB has a role comparable to that of the ALB in full extension. In addition, the PMB resists internal rotational at greater flexion angles (> 90°). Consequently, it is difficult to restore native kinematics with a single graft. Biomechanical analysis of single- versus double-bundle PCL reconstructions (SB PCLR vs DB PCLR) demonstrates improved restoration of native kinematics with a DB PCLR, including resistance to posterior translation throughout flexion (15°-120°) and internal rotation in deeper flexion (90°-120°). Similarly, clinical research demonstrates excellent outcomes following DB PCLR, including functional outcomes comparable to those of anterior cruciate ligament reconstructions, with no significant differences between isolated and multiligament PCL injuries. Compared to SB PCLR, systematic review has demonstrated the superiority of DB PCLR based on objective postoperative stress radiography and International Knee Documentation Committee scores in randomized trials. In addition to reconstruction techniques, recent research has identified other factors that impact kinematics and PCL forces, including decreased tibial slope, which leads to increased graft stresses, and incidence of native PCL injuries. As the understanding of these other contributing factors evolves, so will surgical and treatment algorithms that will further improve patients' outcomes., (Copyright © 2019 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To describe the morphology and distribution of the anterolateral ligament of the knee (ALL) nerve endings, aiming to understand the interaction between the proprioceptive system and knee mechanics., Methods: Twenty ALLs were obtained from fresh frozen cadavers. The ligaments were measured, weighed, and cut. Sections (10 μm) were prepared in hematoxylin and eosin-stained slides to analyze tissue integrity, and 50-μm sections were subjected to immunofluorescence with the protein gene product 9.5 as primary antibody and Alexa Fluor 488 as secondary antibody, followed by microscopic analysis., Results: The ALL was identified in 100% of the dissections, exhibiting a mean (± standard deviation) length of 4.0 ± 0.4 cm, a mean width of 5.5 ± 0.8 mm, and a mean weight of 0.9 ± 0.2 g. The histological sections in hematoxylin and eosin showed dense, well-organized collagen and the presence of vascular tissue. All the specimens analyzed contained type I (Ruffini-like) mechanoreceptors and free nerve endings (type IV), varying from parallel to intertwined fibers. Unclassified nerve endings with different irregular shapes were also found. The neural elements occupied 0.6% ± 0.3% of the ligament area, and most were observed near the origin of ALL insertions., Conclusion: The ALL exhibits a peripheral nerve structure, primarily type I and IV mechanoreceptors. These findings suggest that the ALL is important for the proprioception and anterolateral stabilization of the knee., Clinical Relevance: It is important to understand ALL innervation and infer how an injury could compromise the proprioceptive role of the lateral compartment, as the ligaments contribute dynamically to stability through proprioceptive control of muscle forces. The findings confirm that the ALL is highly innervated by mechanoreceptors and may have a proprioceptive role in conjunction with the lateral collateral ligament in the lateral region of the knee., (Copyright © 2019 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To compare the elongation patterns of the anterior and posterior borders of the anterolateral ligament (ALL) at varying knee flexion angles with the knee in a neutral position without any external forces and with external forces applied, including anterior-posterior translation, internal-external rotation, and varus-valgus angulation., Methods: Eight cadaveric knees were tested in a custom knee testing system. Elongation of the anterior and posterior borders of the ALL was measured using a MicroScribe 3DLX system at knee flexion angles of 0°, 30°, 60°, and 90° and after the application of internal-external rotation, anterior-posterior translation, and varus-valgus angulation., Results: The anterior border showed a slight noncontinuous increase in percentage elongation (0.8% ± 2.2%) whereas the posterior border showed a continuous decrease in percentage elongation (-12.0% ± 2.8%) as knee flexion increased (P < .001). Apart from the elongation of the posterior border at 90° of knee flexion, internal rotation, varus angulation, and anterior translation resulted in a significant increase in the percentage elongation of the anterior and posterior borders at each flexion angle compared with external rotation, valgus angulation, and posterior translation, respectively., Conclusions: The ALL shows different elongation patterns between the anterior and posterior borders, with a continuous decrease in the percentage elongation of the posterior border as knee flexion increases., Clinical Relevance: This study presents useful evidence to resolve the uncertainty regarding the change in length of the ALL at various degrees of knee flexion. This information may be helpful for deciding the optimal knee flexion angle during ALL graft fixation. The findings from this study suggest that graft fixation during ALL reconstructions should be performed at close to full extension of the knee., (Copyright © 2019 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To conduct a systematic literature review to search for studies on the anatomy of the anterolateral ligament (ALL) of the knee, presenting the most accepted findings, as well as the evolution of anatomic information on this structure., Methods: We reviewed the PubMed, MEDLINE, and ClinicalKey databases for anatomic studies on the ALL, involving cadaveric, histologic, and biochemical dissection and/or anatomic imaging. The primary data researched were the presence of the ligament; measures of length, width, and thickness; ligament path; insertions; number of bands; histologic assessment; and innervation., Results: We identified 53 studies. The ALL was found in 82.87% of adult dissections (more easily visualized in fresh cadavers), 74.07% of fetal dissections, and 84.80% of magnetic resonance imaging (MRI) studies. In 29 articles, the ALL was found in 100% of cases. There are 3 ALL insertion points: femoral, tibial, and meniscal. Histologic sections showed dense, well-organized collagen fibers, with an average of 121 fibroblasts/mm 2 in adults, in addition to the presence of vascular and nervous tissue. MRI was shown to be a good examination tool to visualize the ALL, primarily in the coronal plane and with T2-weighted images., Conclusions: The ALL is a distinct structure in the anterolateral portion of the knee. It exhibits typical ligament characteristics and can be visualized on imaging examinations, especially MRI. It has a femoral attachment near the lateral epicondyle, with a trend in recent years showing it to be located posterior and proximal to it, following an anteroinferior trajectory, with an insertion into the lateral meniscus and proximal tibia at the midpoint between the fibular head and Gerdy tubercle. Among the studies, the length of the ALL varied from 30.41 to 59.0 mm, the width ranged between 4.0 and 7.0 mm, and the thickness ranged between 1.0 and 2.0 mm., Clinical Relevance: During the past few years, much controversy has been raised about the correct anatomy of the ALL. The main clinical relevance of this study is not only to end the discussion about the ALL's existence but also to clarify and synthesize the main evidence on the ALL's anatomy, mainly the currently most accepted attachments according to the recent literature, to enable more precise development of biomechanical settings and surgical techniques., (Copyright © 2019 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Paul Segond was a French surgeon who was in practice at the end of the 19th century. A prodigious anatomist, scientist, and surgeon in his day, he is best known for his treatise on the origin of traumatic hemarthrosis of the knee following injury. In this detailed description of the anatomy of the anterolateral aspect of the knee, he describes "a pearly, resistant, fibrous band that is placed under extreme tension when the knee is forcefully rotated internally," which has more recently been described as the anterolateral ligament or a capsular thickening contributing to the anterolateral complex of the knee. His work goes on to speculate about the role of this structure in controlling internal rotation of the knee. The original study was published in French in 1879. Although this work is widely cited, one must question whether many of the citing authors have actually had the opportunity to read it. As such, we sought to unlock this treasure by translating the original study into English and exposing this illuminating, forward-thinking and historical tour de force to the broader orthopaedic community., (Copyright © 2019 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: This study attempted to define a reproducible "safe zone" based on extra- and intra-articular knee anatomy for placing one or 2 accessory portals in the lateral tibiofemoral compartment for posterolateral region viewing., Methods: Standard portals were created in 10 cadaveric knees to enable posterolateral region arthroscopic lateral tibiofemoral joint compartment viewing. After identifying the lateral knee surface tissue "soft spot," an accessory posterolateral portal (A) was created using an 18-gauge spinal needle and 4-mm cannula under direct visualization of a 70° arthroscope through the anteromedial portal. A second accessory portal (B) was then created 1 cm posterior and 1 cm superior to portal A. Accessory portal locations were measured relative to capsular fold and popliteus tendon locations. Distances from the peroneal nerve, lateral collateral ligament, popliteus tendon, and the biceps tendon were determined. Statistical analysis compared portal location differences from key anatomical structures (P < .05)., Results: Accessory portal A (mean ± 95% confidence interval) was located 8.8 ± 2.7 mm from the popliteus tendon, 11.6 ± 2.7 mm from the lateral collateral ligament (LCL), 26.8 ± 2.3 mm from the peroneal nerve, and 4.9 ± 2.5 mm from the biceps tendon. Accessory portal B was located 17.3 ± 2.8 mm from the popliteus tendon, 20 ± 2.8 mm from the LCL, 30.3 ± 3.3 mm from the peroneal nerve, and 7.0 ± 4.8 mm from the biceps tendon. Accessory portal B was located a greater distance from the LCL and the popliteus tendon than portal A (P < .0001)., Conclusions: Using intra- and extra-articular anatomic landmarks, both accessory portals could be safely placed in the lateral tibiofemoral joint compartment to enable posterolateral region viewing. Accessory portals used individually or in combination may enable easier posterolateral region viewing for arthroscopic repair of lateral tibiofemoral compartment structures., Clinical Relevance: Lateral tibiofemoral compartment portals can be safely created to enable improved visibility for complex arthroscopic procedures in the posterolateral viewing region., (Copyright © 2018 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To explore the association between the magnetic resonance imaging (MRI)-measured intercondylar notch dimensions, including the intercondylar notch width (NW) and intercondylar notch width index (NWI), and the risk of anterior cruciate ligament (ACL) injury by performing a meta-analysis of studies that relied on the multiplanar imaging and soft-tissue visualization strengths of MRI., Methods: The MEDLINE, Embase, and SportDiscus databases were searched from inception to March 2017. Observational studies reporting on the associations of the NWI and NW with ACL injury were retrieved. A random-effects model was used to calculate the overall weighted mean difference (WMD) between the ACL injury group and control group., Results: A total of 20 studies were included in this meta-analysis. The combined data showed that subjects with ACL injury, as compared with the control group, had a significantly decreased NW (pooled WMD, -1.53 [95% confidence interval, -1.81 to -1.25]; P < .00001) and NWI (pooled WMD, -0.02 [95% confidence interval, -0.03 to -0.01]; P < .00001). Similar findings were observed in subgroup analyses in terms of different injury mechanisms. No significant difference in NWI was found in the axial view. A significantly decreased NW and NWI were found in other plane views. The sensitivity analyses after the exclusion of studies enrolling only athletes or skeletally immature subjects reached similar outcomes. The Begg rank correlation test showed no publication bias., Conclusions: With the accumulation of evidence, this meta-analysis concluded that the NW and/or NWI measured by MRI was significantly lower in ACL-injured patients than in control subjects. For persons with a narrow intercondylar notch, preventive measures can be prepared for the prevention of ACL injuries., Level of Evidence: Level III, meta-analysis of Level II and III studies., (Copyright © 2018. Published by Elsevier Inc.)

Purpose: To describe the anatomy (quantitative macroscopic and histologic), radiographic parameters of the insertions, and biomechanical characteristics of the medial ligamentous restrictors of the patella (medial patellofemoral ligament [MPFL], medial patellotibial ligament [MPTL], and medial patellomeniscal ligament [MPML]) in cadaveric knees. Because the MPTL and the MPML are not as well known as the MPFL, they were the focus of this study., Methods: MPFLs, MPTLs, and MPMLs from 9 knees were dissected. Histologic evaluations were conducted. Length, width, and insertion relations with anatomic references were determined. Metallic spheres were introduced into the insertion points of each ligament, and anteroposterior and lateral radiographs were taken. The distances of the insertions from the baselines were measured on radiographs. Tensile tests of the ligaments were performed., Results: All the samples showed dense connective tissue characteristic of ligaments. The MPTL was inserted into the proximal tibia (13.7 mm distal to the joint line) and in the distal end of the patella (3.6 mm proximal to the distal border). The MPTL had a length of 36.4 mm and a width of 7.1 mm. The MPML was inserted into the medial meniscus and distally in the patella (5.7 mm proximal to the distal border). Per radiography, on the anteroposterior view, the tibial insertion of the MPTL was 9.4 mm distal to the joint line and in line with the medial border of the medial spine. On the lateral view, the patellar insertions of the MPTL and MPML were 4.8 and 6.6 mm proximal to its distal border, respectively. The MPTL was stiffer than the MPFL (17.0 N/mm vs 8.0 N/mm, P = .024) and showed less deformation in the maximum tensile strength (8.6 mm vs 19.3 mm, P = .005)., Conclusions: The MPTL inserts into the proximal tibia and into the distal pole of the patella. The MPML inserts into the medial meniscus and into the distal pole of the patella. They present with identifiable anatomic and radiographic parameters. Grafts commonly used for ligament reconstructions should be adequate for reconstruction of the MPTL., Clinical Relevance: The study contributes to the anatomic, radiographic, and biomechanical knowledge of the MPTL to improve the outcomes of its reconstruction., (Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To determine the static stabilizing effects of different anatomical structures of the posterolateral corner (PLC) of the knee in the lateral collateral ligament (LCL)-intact state., Methods: Thirteen fresh-frozen human cadaveric knees were dissected and tested using an industrial robot with an optical tracking system. Kinematics were determined for 134 N anterior/posterior loads, 10 N m valgus/varus loads, and 5 N m internal/external rotatory loads in 0°, 20°, 30°, 60°, and 90° of knee flexion. The PLC structures were dissected and consecutively released: (I) intact knee joint, (II) with released posterior cruciate ligament (PCL), (III) popliteomeniscal fibers, (IV) popliteofibular ligament, (V) arcuat and popliteotibial fibers, (VI) popliteus tendon (PLT), and (VII) LCL. Repeated-measures analysis of variance was performed with significance set at P < .05., Results: After releasing the PCL, posterior tibial translation increased by 5.2 mm at 20° to 9.4 mm at 90° of joint flexion (P < .0001). A mild 1.8° varus instability was measured in 0° of flexion (P = .0017). After releasing the PLC structures, posterior tibial translation further increased by 2.9 mm at 20° to 5.9 mm at 90° of flexion (P < .05) and external rotation angle increased by 2.6° at 0° to 7.9° at 90° of flexion (P < .05, vs II). Varus stability did not decrease. Mild differences between states V and VI were found in 60° and 90° external rotation tests (2.1° and 3.1°; P < .05)., Conclusions: The connecting ligaments/fibers to the PLT act as a primary static stabilizer against external rotatory loads and a secondary stabilizer against posterior tibial loads (when PCL is injured). After releasing these structures, most static stabilizing function of the intact PLT is lost. The PLC has no varus-stabilizing function in the LCL-intact knee., Clinical Relevance: Anatomy and function of these structures for primary and secondary joint stability should be considered for clinical diagnostics and when performing surgery in the PLC., (Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To describe the proximity of the lateral critical structures (peroneal nerve [PN], popliteus tendon [PT], lateral collateral ligament [LCL], and articular cartilage [AC]) to the femoral tunnel for outside-in all-epiphyseal anterior cruciate ligament (ACL) reconstruction in reference to knee flexion angle., Methods: All-epiphyseal ACL reconstructions were performed in 12 human cadaveric knees using arthroscopy and outside-in drilling for anatomic femoral tunnel placement that was ensured by identifying the center of the total ACL footprint. Fluoroscopy was used to confirm tunnel position and reconstructions were performed with quadrupled semitendinosus and gracilis autograft with Xtendobutton (Smith & Nephew, Andover, MA) fixation on the femoral side. After reconstruction, the lateral side of the knee was dissected and the LCL, PT, distal and posterior AC, and the PN were identified. The distances of these structures from the center of the exiting femoral tunnel were then measured using a digital caliper at 0°, 30°, 60°, 90°, and 120° of knee flexion. Any gross damage to these structures caused by the femoral drilling was also noted. Data were compiled and the mean and standard deviations (SD) of the distances from the pin to the structures of interest were calculated. The normality of the data at each flexion angle was assessed using Shapiro-Wilk tests (P > .05), and the relationship between flexion angle and average distance was evaluated using repeated measures analysis of variance (P < .05). Any significant relationships were then evaluated using paired t-tests (P < .05) with a Benjamini-Hochberg adjustment for each possible pair of flexion angles. Averages, SD, and P values are reported. A post hoc power analysis was performed., Results: The violation of the LCL was noted in 3 specimens and that of the PT in 1 specimen as a result of femoral tunnel drilling at flexion angles ranging from 90° to 120°. The distance between the PT and the femoral tunnel also decreased significantly (P < .001) with knee flexion with average distances to the center of 8.07 mm at 0°, 7.75 mm at 30°, 6.33 mm at 60°, 4.12 mm at 90°, and 1.89 mm at 120°. The mean ± SD for distances from the femoral tunnel to the center of the PT at 0° was 8.07 ± 7.15, at 30° 7.75 ± 6.66, at 60° 6.33 ± 6.79, at 90° 4.12 ± 5.71, and at 120° 1.89 ± 5.56. As the knee was progressively flexed, the distance between the LCL and the femoral tunnel decreased significantly (P < .001) with an average distance of 6.52 mm at 0°, 6.26 mm at 30°, 4.23 mm at 60°, 2.38 mm at 90°, and 0.4 mm at 120°. The mean ± SD for distances from the femoral tunnel to the center of the LCL at 0° was 6.52 ± 5.93, at 30° 6.26 ± 7.32, at 60° 4.23 ± 7.82, 90° 2.38 ± 7.31, and at 120° 0.4 ± 7.01. The PN was remote from the femoral tunnel at all flexion angles with a mean distance of 42.83 to 59.22 mm. The PN to guide pin distance increased significantly with progressive knee flexion (P < .001). The AC was not damaged in all specimens., Conclusions: The LCL and PT are at significant risk during percutaneous femoral drilling for all-epiphyseal anatomic ACL reconstruction using an outside-in technique. This risk was maximized at 120° flexion and minimized in full extension. These findings suggest that the optimal position for femoral drilling in all-epiphyseal ACL reconstruction is full or near-full extension of the knee that can be accomplished by placing the knee in 30° of flexion (after using fluoroscopic guidance to pass the guide pin past the lateral critical structures) to visualize the footprint of the ACL., Clinical Relevance: Information garnered from this study may help clinicians better understand the risk to the lateral critical structures when an outside-in femoral tunnel is not drilled in the appropriate degree of knee flexion., (Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To characterize the tensile and histologic properties of the anterolateral ligament (ALL), inferior glenohumeral ligament (IGHL), and knee capsule., Methods: Standardized samples of the ALL (n = 19), anterolateral knee capsule (n = 15), and IGHL (n = 13) were isolated from fresh-frozen human cadavers for uniaxial tensile testing to failure. An additional 6 samples of the ALL, capsule, and IGHL were procured for histologic analysis and determination of elastin content., Results: All investigated mechanical properties were significantly greater for both the ALL and IGHL when compared with capsular tissue. In contrast, no significant differences between the ALL and IGHL were found for any property. The elastic modulus of ALL and IGHL samples was 174 ± 92 MPa and 139 ± 60 MPa, respectively, compared with 62 ± 30 MPa for the capsule (P = .001). Ultimate stress was significantly lower (P < .001) for the capsule, at 13.4 ± 7.7 MPa, relative to the ALL and IGHL, at 46.4 ± 20.1 MPa and 38.7 ± 16.3 MPa, respectively. The ultimate strain at failure was 37.8% ± 7.9% for the ALL and 39.5% ± 9.4% for the IGHL; this was significantly greater (P = .041 and P = .02, respectively) for both relative to the capsule, at 32.6% ± 8.4%. The strain energy density was 7.8 ± 3.1 MPa for the ALL, 2.1 ± 1.3 MPa for the capsule, and 7.1 ± 3.1 MPa for the IGHL (P < .001). The ALL and IGHL consisted of collagen bundles aligned in a parallel manner, containing elastin bundles, which was in contrast to the random collagen architecture noted in capsule samples., Conclusions: The ALL has similar tensile and histologic properties to the IGHL. The tensile properties of the ALL are significantly greater than those observed in the knee capsule. CLINICAL RELEVANCE: The ALL is not just a thickening of capsular tissue and should be considered a distinct ligamentous structure comparable to the IGHL in the shoulder. The tensile behavior of the ALL is similar to the IGHL, and treatment strategies should take this into account., (Copyright © 2017 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To determine the location and variability of the anterolateral ligament (ALL) femoral origin., Methods: The ALL was dissected and examined in 52 embalmed specimens, and the femoral origin was isolated. The presence of a bony or soft-tissue attachment, the relation to the lateral collateral ligament, the average diameter of the proximal origin, and the specific location of the origin relative to the lateral femoral epicondyle were recorded., Results: The ALL was present in all 52 specimens, with a mean diameter of 11.85 mm, and was consistently attached to bone in all specimens. The ALL consistently overlapped the lateral collateral ligament near its attachment, with the location of the origin directly on the lateral epicondyle in 12 specimens (23%), with a shared lateral femoral condyle and with the origin slightly posterior and proximal to the lateral epicondyle in 30 specimens (58%), and with the origin completely posterior and proximal to the lateral epicondyle in 10 specimens (19%)., Conclusions: The ALL showed a consistent bony origin overlapping the lateral collateral ligament in all specimens, with some variability in the femoral attachment, ranging from directly on the lateral epicondyle to posterior to the lateral epicondyle., Clinical Relevance: The identification and description of the femoral origin of the ALL are crucial in understanding its role in the stability of the knee, as well as determining the appropriate position for the femoral origin placement in ALL reconstruction., (Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To identify the radiographic position of the origin and insertion of the anterolateral ligament (ALL) of the knee on a lateral radiograph., Methods: Twelve unpaired, fresh-frozen cadaveric knees were dissected to expose the ALL. The origin and insertion of the ALL on each cadaver were then tagged using 2-mm radiopaque beads. True lateral fluoroscopic views of the knee were then obtained, and the distance from known radiographic landmarks was recorded by 2 reviewers., Results: The origin of the ALL was found at a distance that is 37.0 ± 9.2% of the total anterior-posterior length of the femoral condyle from the posterior edge as measured along Blumensaat's line. The insertion was located at a distance that is 56.1 ± 6.9% of the total length of the tibial plateau from the posterior edge. The origin of the ALL is 5 mm posterior to a line from the posterior femoral cortex and 9 mm distal to a line along Blumensaat's line. The insertion is 4 mm anterior to the 50% mark of the anterior-posterior width of the tibia, 14 mm distal to the articular surface., Conclusions: The origin and insertion of the ALL can be accurately identified using intraoperative fluoroscopy., Clinical Relevance: Determining radiographic parameters for the ALL will assist in developing accurate surgical techniques for ALL reconstruction., (Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To categorize and summarize up-to-date anterior cruciate ligament (ACL) research published in Arthroscopy and The American Journal of Sports Medicine and systematically review each subcategory, beginning with ACL anatomy., Methods: After searching for "anterior cruciate ligament" OR "ACL" in Arthroscopy and The American Journal of Sports Medicine from January 2012 through December 2014, we excluded articles more pertinent to ACL augmentation; open growth plates; and meniscal, chondral, or multiligamentous pathology. Studies were subcategorized for data extraction., Results: We included 212 studies that were classified into 8 categories: anatomy; basic science and biomechanics; tunnel position; graft selection; graft fixation; injury risk and rehabilitation; practice patterns and outcomes; and complications. Anatomic risk factors for ACL injury and post-reconstruction graft failure include a narrow intercondylar notch, low native ACL volume, and increased posterior slope. Regarding anatomic footprints, the femoral attachment is 43% of the proximal-to-distal lateral femoral condylar length whereas the posterior border of the tendon is 2.5 mm from the articular margin. The tibial attachment of the ACL is two-fifths of the medial-to-lateral interspinous distance and 15 mm anterior to the posterior cruciate ligament. Anatomic research using radiology and computed tomography to evaluate ACL graft placement shows poor interobserver and intraobserver reliability., Conclusions: With a mind to improving outcomes, surgeons should be aware of anatomic risk factors (stenotic femoral notch, low ligament volume, and increased posterior slope) for ACL graft failure, have a precise understanding of arthroscopic landmarks identifying femoral and tibial footprint locations, and understand that imaging to evaluate graft placement is unreliable., Level of Evidence: Level III, systematic review of Level III evidence., (Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To systematically review current literature on the anterolateral ligament (ALL) of the knee., Methods: We searched the PubMed/Medline database for publications specifically addressing the ALL. We excluded studies not written in English, studies not using human cadavers or subjects, and studies not specifically addressing the ALL. Data extraction related to the incidence, anatomy, morphometry, biomechanics, and histology of the ALL and its relation to the Segond fracture was performed., Results: The incidence of the ALL ranged from 83% to 100%, and this range occurs because of small discrepancies in the definition of the ALL's bony insertions. The ALL originates anterior and distal to the femoral attachment of the lateral collateral ligament. It spans the joint in an oblique fashion and inserts between the fibular head and Gerdy tubercle on the tibia. Exact anatomic and morphometric descriptions vary in the literature, and there are discrepancies regarding the ALL's attachment to the capsule and lateral meniscus. The ALL is a contributor to tibial internal rotation stability, and histologically, it exhibits parallel, crimped fibers consistent with a ligamentous microstructure. The footprint of the ALL has been shown to be at the exact location of the Segond fracture., Conclusions: The ALL is a distinct ligamentous structure at the anterolateral aspect of the knee, and it is likely involved in tibial internal rotation stability and the Segond fracture., Level of Evidence: Level IV, systematic review of anatomic and imaging studies., (Copyright © 2015 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this systematic review was to evaluate the anatomic structure and function of the anterolateral ligament (ALL) of the knee., Methods: The Medline, Embase, and Cochrane databases were screened for all studies related to the ALL of the knee. Two reviewers independently reviewed all eligible articles and the references of these articles. Inclusion and exclusion criteria were applied to all searched studies. Quality assessment was completed for the included studies., Results: Nineteen studies were identified for final analysis. Pooled analysis identified the ALL in 430 of 449 knees (96%) examined. The ligament was found to originate from the region of the lateral femoral epicondyle and insert on the proximal tibia midway between the Gerdy tubercle and the fibular head. The ALL was found to be 34.1 to 41.5 mm in length, 5.1 to 8.3 mm in width above the lateral meniscus, and 8.9 to 11.2 mm in width below the lateral meniscus. By use of magnetic resonance imaging, the ALL was identified in 93% of knees examined (clinical, 64 of 70; cadaveric, 16 of 16). In one case study the ligament was clearly visualized by ultrasound examination. Histologic analysis across 3 studies showed characteristics consistent with ligamentous tissue. Though not shown in biomechanical studies, it is hypothesized that the ALL provides anterolateral stability to the knee, preventing anterolateral subluxation of the proximal tibia on the femur. One study identified a network of peripheral nerves, suggesting a proprioceptive function of the ALL., Conclusions: This systematic review shows the ALL to be a distinct structure with a consistent origin and insertion sites. The ALL is an extra-articular structure with a clear course from the lateral femoral epicondyle region, running anteroinferiorly, to the proximal tibia at a site midway between the Gerdy tubercle and the head of the fibula. The function of this ligament is theorized to provide anterolateral knee stability., Level of Evidence: Level IV, systematic review of cadaveric and imaging studies., (Copyright © 2015 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to summarize the past 10 years of orthopaedic literature to better delineate the femoral origin of the posterior cruciate ligament (PCL)., Methods: A PubMed search was conducted by 2 independent reviewers (M.P., M.V.) using the search terms "posterior cruciate ligament" or "PCL," "femur" or "femoral," and "anatomy" or "origin" or "footprint." Cadaveric and radiographic studies performed between January 1, 2003, and November 30, 2013, were analyzed., Results: Aggregate data from radiographic parameters indicate that the anatomic origin of the anterolateral bundle lies 40% of the distance from the anterior articular surface of the femur and 14.5% of the tangent distance from the Blumensaat line toward the intercondylar notch. The origin of the posteromedial bundle lies 56% from the anterior surface and 36.5% of the tangent distance toward the notch. On the basis of cadaveric data, the center of the anterolateral bundle is 8 mm from the anterior surface (27.5% of the Blumensaat line), 4.7 mm tangent from the Blumensaat line toward the notch (22.5% of the tangent distance), and 3.6 mm from the medial intercondylar ridge; the center of the posteromedial bundle is 11.9 mm from the anterior articular surface (42.5%), 10.9 mm along the tangent line (57.5%), and 3.1 mm from the medial intercondylar ridge., Conclusions: We were able to precisely delineate the femoral origin of the PCL through our systematic review., Clinical Relevance: Our systematic review may assist arthroscopic knee surgeons in placing anatomic tunnels during reconstruction of the PCL., (Copyright © 2015 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of our study was to investigate the relation between posterior tibial slope and anterior cruciate ligament (ACL) rupture in patients with open physes., Methods: A retrospective case-control study was performed comparing skeletally immature patients with an ACL rupture with an age-matched control group. Posterior tibial slope was measured on plain lateral radiographs in both groups by blinded readers, at 2 separate time intervals, using a previously examined and accepted technique., Results: Thirty-two patients were included in the study group (mean age, 13 years; age range, 9 to 17 years) and compared with 32 patients in the control group (mean age, 13 years; age range, 9 to 16 years). The mean posterior tibial slope in the ACL-injured population was 10.0° ± 3° versus 8.5° ± 3° in the control group (P = .0128). Statistical significance was seen in comparisons of slope measurements between the ACL-injured and control groups for 2 of the 3 readers (readers 1 and 3) at both time points (P = .0348 and P = .0051 for reader 1 and P = .0009 and P = .0059 for reader 3). Intrarater reliability proved superior with values correlating with moderate to good reliability, whereas inter-rater reliability values corresponded with fair to moderate reliability. The average posterior tibial slope was 9.5° (range, 3° to 14°) for female patients and 9.8° (range, 2° to 16°) for male patients., Conclusions: On the basis of the results of this study, the data support the notion that a moderate association may exist between an increased posterior tibial slope and ACL injury in pediatric patients with open physes., Level of Evidence: Level III, case-control study., (Copyright © 2015 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to evaluate the shape of the native anterior cruciate ligament (ACL) along its length in relation to the posterior cruciate ligament (PCL) and compare it with the size of the 3 commonly used autografts (bone-patellar tendon-bone [BPTB], single-bundle hamstring, and double-bundle hamstring)., Methods: With the knee in extension, we filled the intercondylar notch with paraffin, fixing the cruciate ligaments in their natural position, in 8 cadaveric specimens. The ACL-PCL tissue specimen, embedded in paraffin, was removed en bloc. Gross sections were prepared in the coronal plane and were evaluated histologically. The width, thickness, and cross-sectional area of both the ACL and PCL were determined. The dimensions of the semitendinosus tendon (ST), gracilis tendon (GT), and BPTB grafts were measured and compared with those of the native ACL., Results: The PCL occupies the largest part of the intercondylar area, leaving only a small space for the ACL in knee extension. The ACL midsubstance has a width of 5 mm, resembling a band shape. Only before its tibial insertion does the ACL fan out and take the form of its tibial attachment. The BPTB graft has a thickness of 5.8 mm, whereas the ST and GT grafts have a thickness of 6.25 mm and 4.5 mm, respectively, and are comparable to the midsubstance of the ACL but undersized in the tibial insertion (P = .0016 for BPTB graft, P = .002 for ST graft, and P = .0003 for GT graft). A quadruple-looped ST-GT graft, with a diameter of 8 mm, is oversized in the midsubstance (P = .0002) but fits better in the tibial attachment., Conclusions: The ACL midsubstance has a width of 5 mm, resembling a band shape. Before its tibial insertion, the ACL fans out like a trumpet, taking the form of its wide tibial attachment., Clinical Relevance: The dimensions of the native ACL have to be considered in graft selection for anatomic ACL reconstruction., (Copyright © 2013 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to review the anatomy of the quadriceps tendon and provide guidelines for harvesting the quadriceps tendon for anterior cruciate ligament (ACL) reconstruction., Methods: Eleven cadaveric knees were dissected, and the quadriceps tendon was analyzed. Multiple measurements of length, depth, and width were taken in a standardized manner for each cadaver and recorded., Results: The quadriceps tendon superficial morphology showed 2 distinct peaks, with the maximum length correlating with the lateral peak. The mean tendon peak length was 88.3 ± 8.4 mm (range, 78.3 to 99.7 mm). The mean width of the quadriceps tendon at its insertion onto the patella was 43.3 ± 5.8 mm (range, 34.3 to 54.1 mm). The quadriceps tendon was noted to be asymmetric, with the maximum tendon length located at 61.6% ± 4.1% of the width from the medial border of the quadriceps tendon insertion. This point was also the maximum tendon depth at insertion., Conclusions: Quadriceps free tendon graft harvesting should begin by locating the apex (maximum length) of the quadriceps tendon (61% of the distance from the patella's medial edge). The surgeon should then harvest a 10-mm-wide graft centered about 2 mm medial to this point, using the depth of a No. 10 scalpel blade (7 mm) as a guide to thickness to harvest an optimal quadriceps free tendon graft for ACL reconstruction., Clinical Relevance: This anatomic study identifies the site of harvest of a quadriceps free tendon autograft (without a patellar bone block) to maximize the length and bulk of the graft for its use in ACL reconstruction., (Copyright © 2012 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to systematically review current arthroscopic and related literature and to characterize the anatomic centrum of the anterior cruciate ligament (ACL) tibial footprint., Methods: On January 31, 2011, 2 independent reviewers performed a Medline search using the terms "anterior cruciate ligament" or "ACL," "tibia" or "tibial," and "anatomy" or "footprint." We included anatomic, cadaveric, and radiographic studies of adult, human, ACL tibial anatomy. Studies not published in the English language, studies published before January 1, 2000, and review articles were excluded. References of included articles were also searched according to our inclusion/exclusion criteria. Included studies were subjectively synthesized, to define the anatomic centrum of the ACL tibial footprint., Results: The Medline search produced 1,224 articles. After application of our inclusion and exclusion criteria and additional search of article references, 19 articles were included and systematically reviewed. With regard to arthroscopically relevant landmarks, (1) in the anterior-to-posterior plane, the anatomic centrum of the ACL tibial footprint as a whole is 15 mm anterior to the posterior cruciate ligament (PCL), the anatomic centrum of the anteromedial bundle is 20 mm anterior to the PCL, and the anatomic centrum of the posterolateral bundle is 11 mm anterior to the PCL and (2) in the medial-to-lateral (ML) plane, the anatomic centrum of the ACL tibial footprint as a whole is two-fifths the ML width of the interspinous distance, the anatomic centrum of the anteromedial bundle is one-half the ML width of the interspinous distance, and the anatomic centrum of the posterolateral bundle is one-fourth the ML width of the interspinous distance., Conclusions: Our results show that the anatomic centrum of the ACL tibial footprint is 15 mm anterior to the PCL and two-fifths the ML width of the interspinous distance., Clinical Relevance: This systematic review of basic science studies may have clinical relevance for surgeons who believe that anatomic ACL reconstruction can result in improved outcomes., (Copyright © 2012 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the posterior septum of the knee and determine the presence of a safe zone that could be removed, without significant damage to blood vessels and nerves., Methods: Nineteen fresh unpaired adult human cadaveric knees, with no macroscopic degenerative or traumatic changes, were used in this study. Microscopic evaluation was performed by analysis of H&E, CD-34, and S-100 staining., Results: The posterior septum of the knee is rich in type II and type IV mechanoreceptors and blood vessels. The superior half has a greater number of blood vessels (21.52 ± 6.36 v 12.05 ± 4.1, P < .001), higher-caliber vessels (2.2 ± 0.89 μm v 1.41 ± 0.45 μm, P < .006), and a greater number of mechanoreceptors per field (type II, 1.8 ± 1.8 v 0.42 ± 1, P = .04; type IV, 22.6 ± 14 v 14.5 ± 9.4, P = .04) than the inferior half of the septum., Conclusions: This study has shown that the posterior septum of the knee is highly vascularized and has a great number of type II and IV mechanoreceptors. The presence of these structures is significantly higher in the superior half of the septum., Clinical Relevance: If debridement of the posterior septum is necessary, it should be done at the inferior aspect so that a greater number of blood vessels and mechanoreceptors can be preserved., (Copyright © 2012 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: Using 3-dimensional high-resolution magnetic resonance imaging (MRI), we sought to compare femoral and tibial tunnel position and resultant graft obliquity with single-bundle anterior cruciate ligament (ACL) reconstruction using transtibial (TT) or anteromedial (AM) portal femoral tunnel reaming techniques., Methods: Thirty patients were prospectively enrolled after primary, autogenous bone-patellar tendon-bone ACL reconstruction by 2 groups of high-volume, fellowship-trained sports medicine surgeons. With the TT technique, an external starting point was used to maximize graft obliquity and femoral footprint capture. By use of high-resolution MRI and imaging analysis software, bilateral 3-dimensional knee models were created, mirrored, and superimposed. Differences between centroids for each femoral and tibial insertion, as well as corresponding ACL/graft obliquity, were evaluated with paired t tests and 2-sided Mann-Whitney nonparametric tests, with P < .05 defined as significant., Results: No significant differences were observed between groups in position of reconstructed femoral footprints. However, on the tibial side, AM centroids averaged 0.8 ± 1.9 mm anterior to native ACL centroids, whereas the TT group centered 5.23 ± 2.4 mm posterior to native ACL centroids (P < .001). Sagittal obliquity was closely restored with the AM technique (mean, 52.2° v. 53.5° for native ACL) but was significantly more vertical (mean, 66.9°) (P = .0001) for the TT group., Conclusions: In this clinical series, AM portal femoral tunnel reaming more accurately restored native ACL anatomy than the TT technique. Although both techniques can capture the native femoral footprint with similar accuracy, the TT technique requires significantly greater posterior placement of the tibial tunnel, resulting in decreased sagittal graft obliquity. When a tibial tunnel is drilled without the need to accommodate subsequent femoral tunnel reaming, more accurate tibial tunnel position and resultant sagittal graft obliquity are achieved., Level of Evidence: Level III, retrospective comparative study., (Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To define a neurovascular safety zone for proper placement of at least 2 posteromedial (PM) portals and to describe a safe intra-articular entrance point based on the location of the PM capsular folds., Methods: Arthroscopy was performed on 10 fresh-frozen cadaveric knees. With the knee flexed 90°, PM portals were created under direct visualization with a 70° arthroscope. The anatomic soft spot between the PM edges of the femoral condyle and the proximal tibia was palpated, and 18-gauge spinal needles were inserted into the joint followed by 5.0-mm cannulas. The PM capsular folds were used to guide portal locations. Four portals (A, B, C, and D) were created in each of the first 3 knees. Portal position was described in relation to the soft spot: through the soft spot (A), 1 cm superior (B), 1 cm posterior (C), and 1 cm inferior (D). Dissection was performed along the path of the cannulas., Results: In the first 3 knees, the most inferior portal (D) always overlapped the course of the saphenous nerve, and the posterior portal (C) always pierced the gastrocnemius musculotendinous junction. Therefore these portals were eliminated from further study for safety reasons, and in the final 7 knees, we studied only the remaining 2 portal placements (A and B). Portals A and B were found to be the safest, with at least 1.5 cm of clearance between the portals and the saphenous nerve in all specimens., Conclusions: At least 2 PM portals can be safely placed in the knee. The soft spot is an appropriate landmark to ensure safe portal entry. The PM capsular folds can help guide intra-articular placement so that damage to surrounding structures can be avoided., Clinical Relevance: We believe that 2 portals would be beneficial when performing complex arthroscopic procedures involving the PM compartment of the knee., (Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to objectively evaluate the anatomic and biomechanical outcomes of anterior cruciate ligament (ACL) reconstruction with transtibial versus anteromedial portal drilling of the femoral tunnel., Methods: Ten human cadaveric knees (5 matched pairs) without ligament injury or pre-existing arthritis underwent ACL reconstruction by either a transtibial or anteromedial portal technique. A medial arthrotomy was created in all cases before reconstruction to determine the center of the native ACL tibial and femoral footprints. A 10-mm tibial tunnel directed toward the center of the tibial footprint was prepared in an identical fashion, starting at the anterior border of the medial collateral ligament in all cases. For transtibial femoral socket preparation (n = 5), a guidewire was placed as close to the center of the femoral footprint as possible. With anteromedial portal reconstruction (n = 5), the guidewire was positioned centrally in the femoral footprint and the tunnel drilled through the medial portal in hyperflexion. An identical graft was fixed and tensioned, and knee stability was assessed with the following standardized examinations: (1) anterior drawer, (2) Lachman, (3) maximal internal rotation at 30°, (4) manual pivot shift, and (5) instrumented pivot shift. Distance from the femoral guidewire to the center of the femoral footprint and dimensions of the tibial tunnel intra-articular aperture were measured for all specimens. Statistical analysis was completed with a repeated-measures analysis of variance and Tukey multiple comparisons test with P ≤ .05 defined as significant., Results: The anteromedial portal ACL reconstruction controlled tibial translation significantly more than the transtibial reconstruction with anterior drawer, Lachman, and pivot-shift examinations of knee stability (P ≤ .05). Anteromedial portal ACL reconstruction restored the Lachman and anterior drawer examinations to those of the intact condition and constrained translation with the manual and instrumented pivot-shift examinations more than the native ACL (P ≤ .05). Despite optimal guidewire positioning, the transtibial technique resulted in a mean position 1.94 mm anterior and 3.26 mm superior to the center of the femoral footprint. The guidewire was positioned at the center of the femoral footprint through the anteromedial portal in all cases. The tibial tunnel intra-articular aperture was 38% larger in the anteroposterior dimension with the transtibial versus anteromedial portal technique (mean, 14.9 mm v 10.8 mm; P ≤ .05)., Conclusions: The anteromedial portal drilling technique allows for accurate positioning of the femoral socket in the center of the native footprint, resulting in secondary improvement in time-zero control of tibial translation with Lachman and pivot-shift testing compared with conventional transtibial ACL reconstruction. This technique respects the native ACL anatomy but cannot restore it with a single-bundle ACL reconstruction. Eccentric, posterolateral positioning of the guidewire in the tibial tunnel with the transtibial technique results in iatrogenic re-reaming of the tibial tunnel and significant intra-articular aperture expansion., Clinical Relevance: Anteromedial portal drilling of the femoral socket may allow for improved restoration of anatomy and stability with ACL reconstruction compared with conventional transtibial drilling techniques., (Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: This study aimed to review the isometric point of the posterior cruciate ligament (PCL) based on insertional locations identified in recent anatomic studies by use of a 3-dimensional knee model., Methods: Ten living subjects with healthy knees were evaluated. High-resolution computed tomography scans were performed at 3 positions of 0°, 90°, and 135°, and 3-dimensional knee images were constructed. Customized software was used to define tibial and femoral insertion points of the PCL, based on recently described anatomy. The femoral attachment site of the PCL was divided into 4 sectors (labeled A through D), and the tibial attachment site was divided into 6 sectors (labeled 1 through 6). Twenty-four virtual PCL bundles were created between these sectors, and their length was measured in the 3 knee flexion positions., Results: In 0° and 90° of knee flexion, the virtual bundle showing the least amount of length change (1.10 ± 0.66 mm) was at sector D-6, that is, a posteromedial bundle inserting into the most posterior femoral sector (sector D) and the most distal tibial sector (sector 6). This change was not significantly different compared with all other virtual bundles with tibial points connected to femoral sector D (P > .05). An isometric position for the PCL (length change <2 mm) could not be found in 135° of knee flexion because of lengthening of all virtual bundles., Conclusions: Our data suggest that the femoral attachment point is more important than the tibial attachment point: any of the 6 tibial bundles attached to the most posterior femoral sector had similar isometric properties., Clinical Relevance: Reproducing normal tibial and femoral anatomy underpins PCL surgical reconstruction. These findings suggest that to perform an isometrically accurate PCL reconstruction, particular attention should be paid to the location of the femoral attachment site, once the tibial footprint has been established. There were no isometric points in any virtual PCL bundle in the fully flexed knee because of excessive lengthening. Therefore, to avoid lengthening of the reconstructed graft, we recommend that fixation is performed at knee flexion angles between 0° and 90° and that patients avoid high flexion during postoperative rehabilitation., (Copyright © 2010 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to compare the axial and sagittal geometry of the distal femur and proximal tibia in men and women with and without noncontact anterior cruciate ligament (ACL) tears to determine whether a difference existed in these groups., Methods: Twenty men and 20 women with noncontact ACL tears and preoperative magnetic resonance imaging scans of their knees were compared with 20 men and 20 women who had magnetic resonance imaging for meniscal pathology. Patients were not matched for age, weight, or height. We measured the anteroposterior dimensions of the femoral condyles, the medial-lateral width of the femur, and the angle of intersection between the transepicondylar axis and the long axis of the femoral condyles. We also measured the anteroposterior dimension of the tibial plateaus, as well as the width of the proximal tibia. Finally, the posterior tibial slope was measured for the medial and lateral tibial plateaus. All dimensional measurements were standardized and compared statistically., Results: When compared with normal men, normal women had proportionally deeper medial (3%, P = .049) and lateral (7%, P < .001) femoral condyles, as well as deeper medial tibial plateaus (5%, P = .025). There were no differences between normal women and women with ACL tears (P = .09 to .83). Men with ACL tears had deeper medial (5%, P = .04) and lateral (10%, P = .01) tibial plateaus, as well as an increased posterior slope of the lateral tibial plateau (12 degrees vs 8 degrees , P = .006), when compared with normal men., Conclusions: We compared normal men and women with those with noncontact ACL tears and found that women's knees were characterized by proportionally deeper medial and lateral femoral condyles, as well as deeper medial tibial plateaus. When compared with normal men, men with ACL tears had deeper medial and lateral tibial plateaus, as well as an increased posterior slope of the lateral tibial plateau., Level of Evidence: Level III, case-control study., (Copyright (c) 2010 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: To clearly define the anatomic relations that exist in the posterior knee under arthroscopic conditions in a cadaveric model and to describe a technique for an all-arthroscopic posterior capsule release., Methods: Seven cadaveric knees were examined under arthroscopic conditions. After a routine diagnostic arthroscopy of the anterior compartment, posteromedial and posterolateral portals were created, the posterior capsule and septum were released, and the distance from the posterior border of the tibial insertion of the posterior cruciate ligament (PCL) to the popliteal artery was measured under direct arthroscopic visualization after capsulotomy. The distances from the posteromedial arthroscopic portal and lateral arthroscopic portal to the saphenous neurovascular bundle and peroneal nerve, respectively, were evaluated., Results: The mean distance between the PCL and popliteal artery was 19.3 mm (range, 15 to 28 mm; SD, 4.27 mm); between the posteromedial portal and saphenous vein, 22.6 mm (range, 16 to 35 mm; SD, 6.7 mm); and between the posterolateral portal and peroneal nerve, 40 mm (range, 30 to 52 mm; SD, 7.94 mm)., Conclusions: When arthroscopic posterior transverse capsulotomy is performed via the author's technique and with the knee flexed to 90 degrees , there is an adequate safe zone between the popliteal neurovascular structures, peroneal nerve, saphenous neurovascular structures and the posterior capsule, posterolateral and posteromedial portals, respectively (minimum, 15 mm)., Clinical Relevance: With a mean distance of 19.3 mm between the PCL and the popliteal artery after capsulotomy, surgeons can feel confident that a safe zone is present for posterior knee arthroscopy. In addition, they can be reassured that posterior portals are safe if created with the knee in the proper position.

Purpose: The purpose of this study was to compare the bundle tension curves and resultant knee kinematics between 2 tensioning protocols in anatomic double-bundle anterior cruciate ligament (ACL) reconstruction., Methods: Anatomic double-bundle ACL reconstruction was performed in 7 male cadaveric knees. Each graft was tensioned to 22 N under 2 conditions: (1) both bundles tensioned at 20 degrees of knee flexion (20/20 protocol) or (2) posterolateral (PL) bundle tensioned at 15 degrees and anteromedial (AM) bundle at 45 degrees (45/15 protocol). Knee kinematics were recorded in response to anterior and combined rotatory loads in the intact, ACL-deficient, and reconstructed states. Bundle tension was recorded dynamically with knee motion and during each loading test., Results: Tensioning both bundles at 20 degrees of knee flexion resulted in a reciprocal bundle tension pattern that was not statistically different; the PL bundle tension was greater than the AM bundle tension in full extension, and the AM bundle tension was greater than the PL bundle tension from 25 degrees to 120 degrees. In the second tensioning protocol, the AM bundle tension was significantly greater than the PL bundle tension at all flexion angles. Both tensioning protocols restored normal knee kinematics., Conclusions: Bundle-tensioning protocol is a variable that has a significant effect on the bundle-loading patterns in double-bundle ACL reconstruction. The 20/20 protocol resulted in AM and PL bundle-loading patterns that were equivalent during dynamic testing, whereas the 45/15 protocol led to excessive tension in the AM bundle in full extension. We recommend equal tensioning of both bundles with the knee at 20 degrees of flexion to restore relatively normal tension curves in each bundle and to avoid excessive stress on the AM bundle., Clinical Relevance: In double-bundle ACL reconstruction, there is no consensus regarding bundle-tensioning protocols. This study provides data on the individual bundle tension curves that result from 2 commonly used tensioning protocols. These data will assist clinicians as the technique and application of double-bundle ACL reconstruction move forward., ((c) 2010 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

Purpose: Our purpose was to evaluate the effect of meniscectomy and meniscal allograft transplant on anterior cruciate ligament (ACL) and knee biomechanics., Methods: A differential variable reluctance transducer was placed in the ACL of 10 human cadaveric knees to record strain. Tibial displacement from a neutral reference was recorded relative to the position of the femur. Testing was performed at 30 degrees, 60 degrees, and 90 degrees of knee flexion. Six cycles of anterior-posterior loads were applied to the limit of 150 N. After a testing cycle, a medial meniscectomy was performed and the testing cycle was repeated. A meniscal allograft transplant was performed, and a final testing cycle was conducted. ACL strain and tibial displacement in the meniscectomy and meniscal allograft states were compared with the intact-knee state., Results: Tibial displacement after meniscectomy significantly increased at all angles. The meniscal allograft transplant restored tibial displacement to normal values at 30 degrees and 90 degrees. ACL strain increased significantly after meniscectomy at 60 degrees and 90 degrees of flexion, and meniscal allograft transplant returned the strain values to normal at 60 degrees and 90 degrees., Conclusions: In most cases medial meniscectomy produced a significant increase in tibial displacement relative to the femur, and meniscal allograft transplantation restored displacement values to normal. Meniscectomy increased ACL strain and meniscal allograft transplant restored strain values to normal in 2 of 3 tested flexion angles., Clinical Relevance: The absence of the medial meniscus exposes the ACL to increased strain, whereas meniscal allograft lowered the strain on the native ACL. This could have implications for those patients undergoing ACL reconstruction who have concomitant removal of the medial meniscus., ((c) 2010 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.)

The anterior cruciate ligament (ACL) consists of 2 anatomic and functional bundles, the anteromedial (AM) and posterolateral (PL) bundle. Depending on the mechanism of injury, there are different injury patterns to the AM and PL bundles, demonstrating a wide spectrum of partial ACL tears. Clinical interest has recently focused on establishing pre- and intraoperative ways of assessing the different types of symptomatic partial ACL injuries in order to perform an individual ACL augmentation according to the specific injury pattern. Theoretically, sparing the intact parts of the ACL may increase vascularization and proprioception, may optimize the accuracy of the ACL reconstruction, and may result in better stability and improved clinical outcome for the patient. However, an isolated reconstruction of the AM or PL bundle is an advanced arthroscopic procedure that requires a precise pre- and intraoperative diagnostic assessment of the injury pattern, an exact arthroscopic knowledge of the anatomic insertion sites, a careful debridement, and bone tunnel placement while preserving the intact parts of the ACL. This article will present the concept of partial ACL tears and will describe the clinical, radiologic, and arthroscopic assessment and the arthroscopic technique of isolated AM or PL bundle augmentation.

Graft positioning is a key issue in anterior cruciate ligament (ACL) reconstruction and even more sensitive in double-bundle reconstruction, where 2 tunnels have to be drilled within the ACL footprints at both the femoral and tibial insertion sites. Specific ancillary instruments have been developed to facilitate the positioning of the 4 sockets necessary when performing anatomic double-bundle ACL reconstruction. This technical note describes the rationale and the step-by-step method of using the specific aimers developed for this purpose. However, a prerequisite for successful double-bundle ACL reconstruction is a good knowledge of ACL footprint anatomy.

The anatomic approach to anterior cruciate ligament (ACL) reconstruction has been a growing trend in orthopaedics. Progress made over the last 7 years has led to a greater understanding of the ACL anatomy and its 2 bundles. Surgeons are now more equipped to restore the native anatomy and knee kinematics than ever before. The University of Pittsburgh experience and technique have been described and have evolved to include several key principles. These include the restoration of native ACL anatomy, insertion sites, and double-bundle tension patterns with the utilization of an accessory medial portal to provide an individualized approach to ACL reconstruction. The purpose of this technical note is to provide surgeons with a technical update regarding the anatomic approach to ACL surgery. Most of this article will be focused on anatomic double-bundle ACL reconstruction, but it must be emphasized that this is a concept rather than just a technique and should be applied to all ACL reconstructions to provide a more anatomic and individualized result.

Improper tunnel placement during anterior cruciate ligament reconstruction may result in residual instability. Proper femoral tunnel orientation relies on tibial tunnel placement with a transtibial technique. Our recommended technique is to use the junction of the anterior border of the superficial medial collateral ligament and the superior border of the gracilis tendon as a reproducible anatomic landmark for the tibial tunnel. In a cadaveric model the mean angle for the tibial tunnel was 65.7 degrees +/- 5.5 degrees in the coronal plane and 75 degrees +/- 7.2 degrees in the sagittal plane. By use of the clock-face method, the mean angle for the femoral tunnel was 44.9 degrees +/- 13 degrees , or approximately the 10:30 position (for a right knee) or 1:30 position (for a left knee).

Purpose: The purpose of this study was to determine the influence of knee flexion angle for drilling the femoral tunnel during anterior cruciate ligament (ACL) reconstruction via the anteromedial (AM) portal on resulting tunnel orientation and length., Methods: In 8 fresh cadaveric knees, the ACL was excised and 2.4-mm guidewires were drilled through the AM bundle footprint using a 5-mm endofemoral aimer via the AM portal. We compared knee flexion angles of 90 degrees , 110 degrees , 130 degrees , and maximum flexion. Anteroposterior-, lateral-, and tunnel-view radiographs were measured to determine tunnel orientation, o'clock position, and direct measurement to determine intra-osseous tunnel length., Results: With regard to tunnel orientation, each increase in knee flexion angle resulted in significantly more horizontal tunnel both on the anteroposterior view and on the lateral view. While on the tunnel view, the pin became more vertical with knee flexion. At 90 degrees , tunnel length was significantly less (27 +/- 9 mm) than at greater angles, and the guidewires were either resting against the posterior cortex or breaching it., Conclusions: The results of this study show the knee flexion angle influences the position of the femoral drilling. It appears in the current study that 110 degrees is optimum, while the 90 degrees pin leads to short tunnel and is so close to the posterior wall there are high risks of posterior wall blow out when drilling the tunnel at its final diameter. Also, 130 degrees of knee flexion is responsible for high tunnel acuity and, finally, maximum flexion being quite variable from one specimen to another cannot be recommended., Clinical Relevance: Tunnels drilled through the AM portal at 90 degrees are at risk of back wall blow out.

Purpose: The aim of this study was to identify the anatomic relation between the posterolateral drill hole and the lateral structures of the knee. The length of the posterolateral tunnel and the feasibility of the EndoButton CL (Smith & Nephew, Andover, MA) as posterolateral graft fixation device was also evaluated., Methods: An anatomic descriptive study was performed on 24 cadaveric knees. The double-bundle anterior cruciate ligament (ACL) was reconstructed using standard arthroscopic techniques and the EndoButton CL fixation system. The study protocol was as follows: first, an arthroscopy with posterolateral pin placement and drilling of the posterolateral tunnel was performed. Subsequently, the lateral structures were dissected and the distance between the pin and the different anatomic structures was measured. From outside in, the length of the posterolateral tunnel was also measured., Results: This study shows that there is no increased risk of injuring the lateral collateral ligament during posterolateral tunnel placement in double-bundle ACL reconstruction, when performed through a low anteromedial portal in high flexion. Furthermore, a safe margin was noted between the posterolateral tunnel and the adjacent lateral gastrocnemius and popliteus tendons. The length of the posterolateral tunnel was between 32 and 44 mm (mean, 36.92 mm)., Conclusions: We conclude that the posterolateral tunnel can be created safely in double-bundle ACL reconstruction without additional risk to the surrounding structures. A 15-mm EndoButton CL fixation device is routinely advised as posterolateral graft fixation in order to avoid the risk of over-advancing the device or overdrilling., Clinical Relevance: This study has shown that there is no risk of iatrogenic lesion to the lateral collateral ligament, lateral gastrocnemius tendon, or popliteus tendon with a posterolateral tunnel drilled through a low anteromedial portal in high flexion.

Purpose: For arthroscopic double-bundle (DB) anterior cruciate ligament (ACL) reconstruction, the size of the available area for tibial bone tunnel placement is crucial. Therefore, tibial insertions of the anteromedial (AM) and posterolateral (PL) bundles in the area intercondylaris anterior (AIA) of the tibia were quantified, landmarks were characterized, and an arthroscopic orientation model was developed., Methods: The tibial insertions of the AM and PL bundles were dissected in 50 human cadaver knees. The footprints were documented on digital photographs and measured using a digital image analysis system., Results: The average tibial ACL insertion area was 114 mm2 and varied considerably in size from 67 to 259 mm2. It was significantly smaller in female knees (P = .04) compared to male knees. The insertion area of the AM bundle was an average of 67 mm2 and that of the PL was 52 mm2. The centers of both bundles were an average of 5 mm apart near the middle of the ACL insertion. Important landmarks for arthroscopic DB bone tunnel placement were the ACL stump, respectively, its anterior and posterior borders; the rims of the articular surfaces of the medial and lateral tibial condyles, which border the AIA; and the posterior horn of the lateral meniscus. The new "tibial square model" indicates a minimum anteroposterior length of 14 to 15 mm for separate AM and PL bone tunnel placement., Conclusions: The prospective area for tibial bone tunnels varied from spacious to very small among the specimens, and the insertions and centers of the AM and PL bundles cannot be exactly anatomically reconstructed. For DB ACL reconstruction, an intraoperative hypothetical situation of 6 mm for the AM tunnel and 5 mm for the PL tunnel may be reasonable when considering an average length of the tibial ACL insertion area of 14 mm in women and 15 mm in men. Individual anatomic variations make it difficult to have general guidelines, but tibial landmarks and the "tibial square model" may assist in individualized bone tunnel placement., Clinical Relevance: Anatomic description of morphology of tibial AM and PL insertions, landmarks, and orientation models for reproducible arthroscopic DB bone tunnel placement.

Purpose: This study was conducted to define what portion of the normal popliteus musculotendinous unit can be visualized during standard diagnostic arthroscopy., Methods: Knee arthroscopy was performed on 5 fresh-frozen cadaveric human knees by use of standard anterolateral and anteromedial portals. The most proximal and distal portions of the popliteus that could be visualized were tagged with arthroscopic sutures. The knees were subsequently dissected, and 4 measurements were made per specimen: the total length of the popliteus tendon; the length of the popliteus tendon that was able to be visualized; the extrasynovial segment at the femoral attachment, which was unable to be visualized; and the distance from the distal-most visible point of the tendon to the musculotendinous junction of the popliteus., Results: The mean total length of the popliteus tendon was 42.0 mm. The arthroscopically tagged portion of the popliteus tendon that was able to be visualized averaged 18.2 mm, or 43.8% of the tendon length. The mean distance from the musculotendinous junction to the visualized portion was 15.1 mm, or 35.8% of the total tendon length. The mean distance from the most proximal visualized portion of the tendon to the femoral attachment was 8.7 mm, or 20.4% of the total tendon length. The musculotendinous junction was not arthroscopically visible in any specimen., Conclusions: On standard knee arthroscopy, less than half of the normal popliteus tendon is visible, and the femoral insertion and musculotendinous junction are not visualized. Because most reported popliteus injuries have occurred here, reliance on arthroscopic visualization alone is inadequate., Clinical Relevance: The limitations of arthroscopic visualization of the normal popliteus tendon have implications for the diagnosis and treatment of posterolateral corner injuries.

Purpose: The purpose of this study was to evaluate the accuracy of radiographic measurements of the intercondylar notch., Methods: Radiographs of 10 cadaveric knees were obtained via the 3 methods reported in the literature (Holmblad 45 degree, Holmblad 70 degree, and Rosenberg views), after removal of the patella and surrounding soft tissues. The anterior outlet of the intercondylar notch of each knee was then outlined with barium paste, and radiography was repeated. A total of 1,770 radiographs were obtained for the 10 knees. Six measurements of the anterior outlet of the intercondylar notch were made from each radiograph and corrected for magnification. Finally, the notch width index was calculated. Caliper measurements were subsequently made of each knee to compare the size of the anterior outlet of the notch with the radiographic measurements with and without barium., Results: There were statistically significant differences in caliper measurements compared with all but one radiographic measurement obtained from the Holmblad 45 degree, Holmblad 70 degree, and Rosenberg views. The radiographs taken with barium outlining the intercondylar notch clearly showed the inability to accurately identify the anterior outlet on radiographs., Conclusions: Even under optimal conditions, correcting for technique, projection, and magnification, most of the radiographic measurements of the anterior outlet of the intercondylar notch were inaccurate. The notch width index calculated from the Holmblad 70 degree view appears to be the only accurate radiographic measurement., Clinical Relevance: This controlled laboratory study shows that clinicians should use caution when basing conclusions on radiographic measurements of the intercondylar notch.

Purpose: To identify the structure of the iliotibial tract at knee level, as well as its insertions, layer arrangement, and relationship with other structures of the lateral region of the knee and to compare the findings with available literature., Methods: Ten detailed anatomic dissections were performed by using incisions as recommended by the literature in fresh cadaver knees identifying the iliotibial tract components., Results: The authors observed an iliotibial tract arrangement in superficial, deep, and capsular-osseous layers. Insertions have been described as follows: at linea aspera, at the upper border of the lateral epicondyle, at the patella, and at Gerdy's tibial tuberculum and across the capsular-osseous layer., Conclusions: The iliotibial tract (ITT) has important interconnections to the femur, the patella, and the lateral tibia; the iliopatellar band joins the ITT to the patella through the superficial oblique retinaculum and the lateral femoropatellar ligament, and the ITT capsular-osseous layer presents differentiated fibers in an arched arrangement that borders the femoral condyle and inserts laterally to the Gerdy's tubercle., Clinical Relevance: The iliotibial tract can be considered as an anterolateral knee stabilizer, particularly its capsular-osseous layer, which, together with the anterior cruciate ligament, constitutes a functional unit forming a spatial "horseshoe" form. The detailed description of the structures forming iliotibial tract plays an important role in the study of knee instabilities. Its important tibial, femoral, and patellar connections are described so that better understanding of tibial femoral instability on the lateral side as well as patellofemoral instability can be achieved and mechanisms of repair can be conceived.

Purpose: The objectives of this study were to show the results of patellofemoral joint imaging in healthy volunteers, to propose a standardization of the technique, and to test the statistical correlation and reliability of the different imaging results., Methods: In 30 healthy police academy student volunteers of both sexes, standard knee radiographs and computed tomography (CT) scans were obtained. The angles and distances were measured, and a statistical analysis was applied. The results are presented as mean +/- 2 SDs throughout., Results: The mean Laurin lateral patellofemoral angle on radiographs was 16.4 degrees +/- 8.7 degrees. The mean Insall-Salvati and Caton-Deschamps indexes were 1.09 +/- 0.24 and 0.95 +/- 0.29, respectively. The CT scan values for tilt were determined for the lateral patellofemoral angle by use of both facets (-8.1 degrees +/- 9.8 degrees), the Laurin lateral patellofemoral angle (8.1 degrees +/- 14.5 degrees), the condyle-patellar angle with the lateral facet (14.5 degrees +/- 14 degrees), and the patella major axis (-11.1 degrees +/- 10.6 degrees). The sulcus angle, congruence angle (Merchant angle), and condyle-lateral angle were also obtained on CT scans, with mean values of 139.7 degrees +/- 20.4 degrees , 5.15 degrees +/- 32.6 degrees , and 22.1 degrees +/- 9 degrees , respectively. The tibiofemoral rotation was assessed with the indexes for the distance between the trochlear groove and anterior tibial tuberosity and the distance between the posterior femoral dome and anterior tibial tuberosity. The values for these two indexes were 13.6 +/- 8.8 mm and 17.8 +/- 9.2 mm, respectively. Some parameters showed sex differences., Conclusions: There are good statistical correlations between some of the tilt values on the radiographs and CT scans, indicating that they move together. The values on the CT scans show good reliability. The CT scans and radiographs are good tests by which to evaluate and quantify patellar alignment., Level of Evidence: Level I, testing of previously developed diagnostic criteria.