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Context: Anterior cruciate ligament injuries are directly related to the control of dynamic knee valgus in the landing of a jump, and this is mainly due to the correct activation and neuromuscular function of the lower-extremity muscles. The aim of the study is to assess the relationship between lower limb muscle activity during a single-legged drop jump and knee frontal plane projection angle (FPPA). Design: A correlation study. Methods: Thirty healthy collegiate female athletes were included in the study. Main outcomes measures were peak knee FPPA and muscle activity (% of maximal voluntary isometric contraction). Peak knee FPPA during a single-legged drop jump test was identified using a 2-dimensional motion analysis system. Muscle activity was assessed using a surface electromyograph for gluteus maximus, gluteus medius, biceps femoris, semitendinosus, vastus medialis quadriceps, vastus lateralis quadriceps, medial gastrocnemius, and lateral gastrocnemius. All variables were assessed for both dominant and nondominant limbs. A correlation analysis between peak knee FPPA and muscle activity was performed. Statistical significance was set at P <.05. Results: A mean peak knee FPPA of 14.52° and 13.38° was identified for dominant and nondominant limb single-legged drop jump test, respectively. Muscle activity (% of maximal voluntary isometric contraction) for muscles assessed ranged from 43.97% to 195.71% during the single-legged drop jump test. The correlation analysis found no significant correlation between any of the muscles assessed and peak knee FPPA during the single-legged drop jump test (Pearson coefficient between −.3 and.1). Conclusions: There is no association between muscle activity from the lower limb muscles and the knee FPPA during a single-legged drop jump in female athletes. Thus, different muscle properties should be assessed in order to understand such an important movement as the knee FPPA during a jump. [ABSTRACT FROM AUTHOR]

Background: Data are lacking as to when a meniscal allograft transplant (MAT) may be biomechanically superior to a partially resected lateral meniscus. Hypothesis: Lateral MAT using a bone bridge technique would restore load distribution and contact pressures in the tibiofemoral joint to levels superior to those of a partial lateral meniscectomy. Study Design: Controlled laboratory study. Methods: Eleven fresh-frozen human cadaveric knees were evaluated in 5 lateral meniscal testing conditions (native, one-third posterior horn meniscectomy, two-thirds posterior horn meniscectomy, total meniscectomy, MAT) at 3 flexion angles (0°, 30°, and 60°) under a 1600-N axial load. Pressure sensors were used to acquire contact pressure, contact area, and peak contact pressure within the tibiofemoral joint. Results: Limited (one-third and two-thirds) partial lateral posterior horn meniscectomy showed no significant increase in mean and peak contact pressures as well as no significant decrease in contact area compared with the intact state. Total meniscectomy significantly increased mean contact pressure at 0° and 30° (P =.008 and P <.001, respectively), increased peak contact pressure at 30° (P =.04), and decreased mean contact area in all flexion angles compared with the native condition (P <.01). Lateral MAT significantly improved mean contact pressure compared with total meniscectomy at 0° and 30° (P =.002 and P =.003, respectively) and increased contact area at 30° and 60° (P =.003 and P =.009, respectively), although contact area was still significantly smaller (24.1%) after MAT relative to the native meniscus (P = 0.015). However, allograft transplant did not result in better tibiofemoral contact biomechanics compared with limited partial meniscectomy (P >.05). Conclusion: The peripheral portion of the lateral meniscus provided the most important contribution to the distribution of contact pressure across the tibiofemoral joint in the cadaveric model. Total meniscectomy significantly increased mean and peak contact pressure in the cadaveric model and decreased contact area. Lateral MAT restored contact biomechanics close to normal but was not superior to the partially meniscectomized status. Clinical Relevance: Surgeons should attempt to preserve a peripheral rim of the posterior lateral meniscus. Meniscal allograft transplant appears to improve but not normalize mean contact pressure and contact area relative to total lateral meniscectomy. [ABSTRACT FROM AUTHOR]

This study investigated the effects of plyometric training on lower‐limb muscle strength and knee biomechanical characteristics during the landing phase. Twenty‐four male subjects were recruited for this study with a randomised controlled design. They were randomly divided into a plyometric training group and a traditional training group and underwent training for 16 weeks. Each subject was evaluated every 8 weeks for knee and hip isokinetic muscle strength as well as knee kinematics and kinetics during landing. The results indicated significant group and time interaction effects for knee extension strength (F = 74.942 and p = 0.001), hip extension strength (F = 99.763 and p = 0.000) and hip flexion strength (F = 182.922 and p = 0.000). For landing kinematics, there were significant group main effects for knee flexion angle range (F = 4.429 and p = 0.047), significant time main effects for valgus angle (F = 6.502 and p = 0.011) and significant group and time interaction effects for internal rotation angle range (F = 5.475 and p = 0.008). The group main effect for maximum knee flexion angle was significant (F = 7.534 and p = 0.012), and the group and time interaction effect for maximum internal rotation angle was significant (F = 15.737 and p = 0.001). For landing kinetics, the group main effect of the loading rate was significant (F = 4.576 and p = 0.044). Significant group and time interaction effects were observed for knee extension moment at the moment of maximum vertical ground reaction force (F = 5.095 and p = 0.010) and for abduction moment (F = 8.250 and p = 0.001). These findings suggest that plyometric training leads to greater improvements in hip and knee muscle strength and beneficial changes in knee biomechanics during landing compared to traditional training. Highlights: Plyometric training changes landing biomechanics.Changes help to reduce the risk of ACL injury.Changes from long‐term training are more noticeable. [ABSTRACT FROM AUTHOR]

This study aimed to analyze the stress and strain changes of the anterior cruciate ligament (ACL) at different knee flexion angles using a three-dimensional finite element model. Computed tomography and magnetic resonance imaging scans were performed on the right knee of 30 healthy adult volunteers. The imaging data were used to construct a three-dimensional finite element model of the knee joint. The magnitude and concentration area of stress and strain of ACL at knee flexion angles 0°, 30°, 60° and 90° were assessed. The magnitude of stress remained consistent at 0–30° (P > 0.999) and decreased at 30–90° (P < 0.001, P = 0.005, respectively), while the magnitude of strain increased between 0° and 30° (P = 0.004) and decreased between 30° and 90° (P < 0.001, P = 0.004, respectively). The stress concentration area remained consistent at the proximal end, midsubstance, and distal end between 0° and 60° (P > 0.05). The concentration area of strain increased at the proximal end, decreased at the midsubstance between 0° and 30°, and remained consistent between 30° and 90° (P < 0.001). At the low knee flexion angle, ACL's magnitude of stress and strain reached the peak, and the concentration area of ACL strain gradually shifted from midsubstance to the proximal end. [ABSTRACT FROM AUTHOR]

Meniscus tears, a prevalent knee joint injury, can significantly hinder joint functionality. Thus, the control of meniscus tears holds significant importance in preserving the joint's regular functionality. A non-invasive approach involves the recommendation of off-loading insoles; which therapists often prescribe based on their clinical experience. Based on the variety of meniscus tear types, it is essential to assess the effectiveness of different insoles when interacting with these distinct tears. This evaluation can be achieved through biomechanical investigations. To address this requirement, the present study utilized medical imaging to establish the precise lower limb geometry. To refine the acquired geometry, both longitudinal and radial tears were applied to the meniscus's geometry. The subsequent phase entails reconstructing the design of three off-loading insole models currently available in the Iranian market. The outcomes of these models demonstrate that the three-layer insole without honeycombs leads to a stress reduction of 1.1% at the apex of the radial tear. When dealing with a longitudinal tear situated on the inner meniscus, the application of a three-layer insole equipped with a honeycomb structure results in a 15% stress reduction. Utilizing a single layer silicone insole results in an 8% decrease in stress on the external meniscus during longitudinal tears. Hence, the three-layer insole incorporating a honeycomb design is effective for managing longitudinal tears on the inner meniscus. Moreover, the research outcomes indicate that, when comparing the two tear types, longitudinal tears carry a greater risk than radial tears, exhibiting an increased likelihood of worsening. [ABSTRACT FROM AUTHOR]

Objective: This study aim to quantify the differences in knee biomechanics during gait between knee osteoarthritis (KOA) patients and healthy individuals. Methods: Twenty KOA patients (4 males and 16 females, 66.2 ± 7.7 years) and twenty controls (16 males and 4 females, 64.8 ± 5.4 years) were recruited for gait test using the motion capture system and force-platform system. The spatiotemporal parameters, knee kinematics and kinetics, and tibiofemoral contact force (TFCF) were calculated using an improved musculoskeletal model. Results: KOA patients walked with reduced speed (48.6 %), stride length (32.9 %), stride height (33.0 %), time proportions of single-support phases (19.2 %), increased gait cycle time (31.0 %), time proportions of stance (8.5 %) and double-support phases (57.7–75.9 %). KOA patients had significant smaller peak flexion angle (29.1 %), flexion ROM (50.6 %) and peak flexion moment (90.2 %), greater peak adduction moment (KAM) (40.7 %), peak rotation moments (KRM) (50.0 %), KAM impulse (106.2 %) and KRM impulse (126.0 %). In proximodistal direction, greater medial TFCF impulse (238 %), total and medial first-peak TFCF (9.6 % and 15.2 %), and smaller lateral peak TFCF (33.3 %) and TFCF impulse (38.4 %) were found in KOA patients. Besides, significant differences were found in the total, medial and lateral peak TFCFs and TFCF impulses in mediolateral direction, and the medial and lateral TFCFs and TFCF impulses in anteroposterior direction. Conclusions: Significant differences were found in the spatiotemporal parameters, knee kinematics and kinetics, and TFCF between the two groups. The results of this study have important implication for clinicians and rehabilitation physicians. These quantified biomechanical differences can provide data support for the personalized and quantified rehabilitation strategies, give suggestions for the exercises of KOA patients, help monitor disease, evaluate surgical treatment, and develop more effective preoperative planning and postoperative rehabilitation strategies.

In recent years, the nexus between genetics and biomechanics has garnered significant attention, elucidating the role of genomic determinants in shaping the biomechanical attributes of human joints, specifically the knee. This review seeks to provide a comprehensive exploration of the molecular basis underlying knee joint locomotor function. Leveraging advancements in genomic sequencing, we identified specific genetic markers and polymorphisms tied to key biomechanical features of the knee, such as ligament elasticity, meniscal resilience, and cartilage health. Particular attention was devoted to collagen genes like COL1A1 and COL5A1 and their influence on ligamentous strength and injury susceptibility. We further investigated the genetic underpinnings of knee osteoarthritis onset and progression, as well as the potential for personalized rehabilitation strategies tailored to an individual’s genetic profile. We reviewed the impact of genetic factors on knee biomechanics and highlighted the importance of personalized orthopedic interventions. The results hold significant implications for injury prevention, treatment optimization, and the future of regenerative medicine, targeting not only knee joint health but joint health in general.

Force attenuation during landing requires coordinated motion of the ankle, knee, hip, and trunk, and strategies may differ between sexes. Sagittal plane coordination of the ankle/knee, knee/hip, and knee/trunk, and lower extremity and trunk kinematics and kinetics was compared throughout landing between 28 males and 28 females. Coordination was assessed with a modified vector coding technique and binning analysis. Total support moments (TSM), each joint's percent contribution, and timing of the TSM were compared. Females landed with less isolated knee flexion in the ankle/knee, knee/hip, and knee/trunk couplings, but more simultaneous ankle/knee flexion, less simultaneous knee flexion/hip extension, and more simultaneous trunk/knee flexion. Females landed with larger plantarflexion angles from 0–16% and smaller trunk flexion angles from 0–78%. In females, absolute TSM were larger from 0–6% and smaller from 42–100%, and normalized TSM were larger from 0–8% and 26–42%. Females had greater ankle contribution to the TSM from 14–15% and 29–35%, smaller absolute peak TSM, and the peak TSM occurred earlier. Females compensated for less isolated knee flexion with greater simultaneous ankle/knee flexion early in landing and knee/trunk flexion later in landing. Coordination and TSM differences may influence force attenuation strategies and have implications for knee injury disparity between sexes. [ABSTRACT FROM AUTHOR]

The menisci increase the contact area of load bearing in the knee and thus disperse the mechanical stress via their circumferential tensile fibers. Traumatic meniscus injuries cause mechanical symptoms in the knee, and are more prevalent amongst younger, more active patients, compared to degenerative tears amongst the elderly population. Traumatic meniscus tears typically result from the load-and-shear mechanism in the knee joint. The treatment depends on the size, location, and pattern of the tear. For non-repairable tears, partial or total meniscal resection decreases its tensile stress and increases joint contact stress, thus potentiating the risk of arthritis. A longitudinal vertical tear pattern at the peripheral third red-red zone leads to higher healing potential after repair. The postoperative rehabilitation protocols after repair range from immediate weight-bearing with no range of motion restrictions to non-weight bearing and delayed mobilization for weeks. Pediatric and adolescent patients may require special considerations due to their activity levels, or distinct pathologies such as a discoid meniscus. Further biomechanical and biologic evidence is needed to guide surgical management, postoperative rehabilitation protocols, and future technology applications for traumatic meniscus injuries.

Context: A limitation of previous studies on squatting mechanics is that the influence of trunk and shank inclination on the knee-extensor moment (KEM) has been studied in isolation. Objective: The purpose of the current study was to determine the influence of segment orientation on the KEM during freestanding barbell squatting. Design: Repeated-measures cross sectional. Setting: University research laboratory. Participants: Sixteen healthy individuals (8 males and 8 females). Intervention: Each participant performed 8 squat conditions in which shank and trunk inclinations were manipulated. Main Outcome Measures: 3D kinematic and kinetic data were collected at 250 and 1500 Hz, respectively. Regression analysis was conducted to identify the individual relationships between the KEM and the trunk and shank inclination at 60° and 90° of knee flexion. To identify the best predictor(s) of the KEM, stepwise regression was implemented. Results: Increased shank inclination increased the KEM (P <.001, R2 =.21–.25). Conversely, increased trunk inclination decreased the KEM (P <.001, R2 =.49–.50). For the stepwise regression, trunk inclination entered first and explained the greatest variance in the KEM (all P <.001, R2 =.49–.50). Shank inclination entered second (all P <.010, R2 =.53–.54) and explained an additional 3% to 5% of the variance. Conclusions: Our results confirm that inclination of the trunk and shank have an opposing relationship with the KEM. Increased forward shank posture increases the KEM, while increased forward trunk posture decreases the KEM. However, when viewed in combination, the trunk was the superior predictor of the KEM, highlighting the fact that increased quadriceps demand created by a forward shank can be offset by trunk inclination. [ABSTRACT FROM AUTHOR]

Purpose: Passive tibiofemoral anterior-posterior (AP) laxity has been extensively investigated after posterior cruciate ligament (PCL) single-bundle reconstruction. However, the PCL also plays an important role in providing rotational stability in the knee. Little is known in relation to the effects of PCL single-bundle reconstruction on passive tibiofemoral rotational laxity. Gait biomechanics after PCL reconstruction are even less understood. The aim of this study was a comprehensive prospective biomechanical in vivo analysis of the effect of PCL single-bundle reconstruction on passive tibiofemoral rotational laxity, passive anterior-posterior laxity, and gait pattern.Methods: Eight patients undergoing PCL single-bundle reconstruction (seven male, one female, mean age 35.6 ± 6.6 years, BMI 28.0 ± 3.6 kg/m2) were analyzed preoperatively and 6 months postoperatively. Three of the eight patients received additional posterolateral corner (PLC) reconstruction. Conventional stress radiography was used to evaluate passive translational tibiofemoral laxity. A previously established rotometer device with a C-arm fluoroscope was used to assess passive tibiofemoral rotational laxity. Functional gait analysis was used to examine knee kinematics during level walking.Results: The mean side-to-side difference (SSD) in passive posterior translation was significantly reduced postoperatively (12.1 ± 4.4 mm vs. 4.3 ± 1.8 mm; p < 0.01). A significant reduction in passive tibiofemoral rotational laxity at 90° knee flexion was observed postoperatively (27.8° ± 7.0° vs. 19.9° ± 7.5°; p = 0.02). The range of AP tibiofemoral motion during level walking was significantly reduced in the reconstructed knees when compared to the contralateral knees at 6-month follow-up (16.6 ± 2.4 mm vs. 13.5 ± 1.6 mm; p < 0.01).Conclusion: PCL single-bundle reconstruction with optional PLC reconstruction reduces increased passive tibiofemoral translational and rotational laxity in PCL insufficient knees. However, increased passive tibiofemoral translational laxity could not be fully restored and patients showed altered knee kinematics with a significantly reduced range of tibiofemoral AP translation during level walking at 6-month follow-up. The findings of this study indicate a remaining lack of restoration of biomechanics after PCL single-bundle reconstruction in the active and passive state, which could be a possible cause for joint degeneration after PCL single-bundle reconstruction.

Model reproducibility is a point of emphasis for the National Institutes of Health (NIH) and in science, broadly. As the use of computational modeling in biomechanics and orthopedics grows, so does the need to assess the reproducibility of modeling workflows and simulation predictions. The long-term goal of the KneeHub project is to understand the influence of potentially subjective decisions, thus the modeler's “art”, on the reproducibility and predictive uncertainty of computational knee joint models. In this paper, we report on the model calibration phase of this project, during which five teams calibrated computational knee joint models of the same specimens from the same specimen-specific joint mechanics dataset. We investigated model calibration approaches and decisions, and compared calibration workflows and model outcomes among the teams. The selection of the calibration targets used in the calibration workflow differed greatly between the teams and was influenced by modeling decisions related to the representation of structures, and considerations for computational cost and implementation of optimization. While calibration improved model performance, differences in the postcalibration ligament properties and predicted kinematics were quantified and discussed in the context of modeling decisions. Even for teams with demonstrated expertise, model calibration is difficult to foresee and plan in detail, and the results of this study underscore the importance of identification and standardization of best practices for data sharing and calibration. [ABSTRACT FROM AUTHOR]

The menisci increase the contact area of load bearing in the knee and thus disperse the mechanical stress via their circumferential tensile fibers. Traumatic meniscus injuries cause mechanical symptoms in the knee, and are more prevalent amongst younger, more active patients, compared to degenerative tears amongst the elderly population. Traumatic meniscus tears typically result from the load-and-shear mechanism in the knee joint. The treatment depends on the size, location, and pattern of the tear. For non-repairable tears, partial or total meniscal resection decreases its tensile stress and increases joint contact stress, thus potentiating the risk of arthritis. A longitudinal vertical tear pattern at the peripheral third red-red zone leads to higher healing potential after repair. The postoperative rehabilitation protocols after repair range from immediate weight-bearing with no range of motion restrictions to non-weight bearing and delayed mobilization for weeks. Pediatric and adolescent patients may require special considerations due to their activity levels, or distinct pathologies such as a discoid meniscus. Further biomechanical and biologic evidence is needed to guide surgical management, postoperative rehabilitation protocols, and future technology applications for traumatic meniscus injuries. [ABSTRACT FROM AUTHOR]

This study aimed to develop and validate a novel flexion axis concept by calculating the points on femoral condyles that could maintain constant heights during knee flexion. Twenty-two knees of 22 healthy subjects were investigated when performing a weightbearing single leg lunge. The knee positions were captured using a validated dual fluoroscopic image system. The points on sagittal planes of the femoral condyles that had minimal changes in heights from the tibial plane along the flexion path were calculated. It was found that the points do formulate a medial-lateral flexion axis that was defined as the iso-height axis (IHA). The six degrees of freedom (6DOF) kinematics data calculated using the IHA were compared with those calculated using the conventional transepicondylar axis and geometrical center axis. The IHA measured minimal changes in proximal–distal translations and varus–valgus rotations along the flexion path, indicating that the IHA may have interesting clinical implications. Therefore, identifying the IHA could provide an alternative physiological reference for improvement of contemporary knee surgeries, such as ligament reconstruction and knee replacement surgeries that are aimed to reproduce normal knee kinematics and medial/lateral soft tissue tensions during knee flexion. [ABSTRACT FROM AUTHOR]

The frequency of lateral unicompartmental knee arthroplasty is estimated at 1% of the total volume of knee arthroplasties, according to contemporary literature. Recent studies analyzing this type of surgical intervention indicate that when performed with proper indications and technical accuracy, it is equally effective and safe as total knee arthroplasty. Potential advantages of partial knee replacement include reduced invasiveness compared to total knee arthroplasty, lower perioperative blood loss, faster patient rehabilitation, and preservation of native joint proprioception. However, it is important to consider that successful implementation of lateral unicompartmental knee arthroplasty requires not only appropriate patient selection but also technical proficiency, advanced operating room equipment, and precise surgical techniques performed by experienced surgeons. Failure to meet these conditions can negate the potential benefits and may lead to early revision surgery. It is evident that unicompartmental knee arthroplasty is not simply a half-operation of total joint replacement, and the lateral compartments partial arthroplasty only shares general similarities with the more popular and established medial unicompartmental knee arthroplasty. The differences lie primarily in the complex anatomy and biomechanics of the lateral compartment, which present a challenging task even with the use of modern anatomically designed implants. The development of robotic surgery and personalized joint implants may help overcome these challenges more effectively. However, in our current routine practice, we rely on conventional instruments and strive to optimize our techniques. The authors of this article aim to provide an overview of the contemporary understanding of the anatomy and biomechanics of the lateral compartment of the knee and the specific technical aspects related to partial lateral arthroplasty using a fixed tibial platform implant.

within 50 milliseconds of initial contact, but are limited by imprecise timing and nondirect data acquisition. The objective of this study was to precisely quantify the timing associated with ligament strain during simulated landing and injury events. The hypotheses tested were that the timing of peak strain following initial contact would differ between ligaments and that peak strain timing would be independent of the injury-risk profile emulated during simulated landing. A mechanical impact simulator was used to perform landing simulations based on various injury-risk profiles that were applied to each specimen in a block-randomized order. The ACL and medial collateral ligament were instrumented with strain gauges that recorded continuously. The data from 35 lower-extremity specimens were included for analysis. Analysis of variance and Kruskal--Wallis tests were used to determine the differences between timing and profiles. The mean time to peak strain was 53 (24) milliseconds for the ACL and 58 (35) milliseconds for the medial collateral ligament. The time to peak ACL strain ranged from 48 to 61 milliseconds, but the timing differences were not significant between profiles. Strain timing was independent of injury-risk profile. Noncontact ACL injuries are expected to occur between 0 and 61 milliseconds after initial contact. Both ligaments reached peak strain within the same time frame. [ABSTRACT FROM AUTHOR]

Posterolateral corner knee injuries are clinically significant, and often require surgical reconstruction. The optimal knee brace following posterolateral corner reconstructions has not yet been determined via clinical nor biomechanical study. We sought to evaluate the stiffness of six types of knee braces to determine the ideal brace type for reducing varus forces, which may have clinical utility for posterolateral corner knee reconstruction rehabilitation. Six different groups of knee braces underwent mechanical testing: cruciate braces, cruciate braces with a valgus bend, medial unloaders, articulating sleeves, hinged braces, and tri-panel immobilizers. Each brace was fitted to the same fiberglass leg model and was secured to the testing apparatus. Force was applied under four-point bending to generate a varus moment about the artificial knee. The stiffness in Newtons per millimeter (N/mm) of each brace was calculated from the slope of the force-displacement curve. The cruciate brace with a valgus bend had the highest average stiffness at 192.61 N/mm (SD 28.53). The articulating sleeve was the least stiff with an average stiffness of 49.86 N/mm (SD 8.99). Stiffness of the cruciate brace was not statistically different compared to cruciate valgus (p = 0.083) or medial unloader (p = 0.098). In this experimental design, a cruciate brace with a valgus bend was shown to have the highest overall stiffness, while an articulating sleeve had the lowest stiffness. Future work will investigate whether this translates into clinical performance. [ABSTRACT FROM AUTHOR]

The pilot study aimed to determine whether the time from injury to surgery influences on postoperative knee biomechanics during walking in patients with anterior cruciate ligament reconstruction (ACLR). Thirty-two patients with unilateral ACLR (early, 10 patients; delayed, 22 patients) and 30 control subjects participated in this study. All examinations for patients with ACLR were performed preoperatively and at 12 months postoperatively and comprised passive knee joint laxity, knee muscle strength, and knee kinematics and kinetics during walking. At both time points, there were no significant differences in passive knee joint laxity and knee muscle strength between the early ACLR and delayed ACLR groups. Preoperatively, both the early ACLR and delayed ACLR patients exhibited significantly reduced knee extension movement from midstance to terminal stance compared to the control subjects. Moreover, the delayed ACLR patients exhibited significantly decreased peak external knee flexion moment compared to the control subjects. At 12 months postoperatively, the early ACLR patients showed significant improvement in knee extension movement from midstance to terminal stance compared to pre-ACLR, while the delayed ACLR patients did not show significant improvement in this knee extension movement. It can be concluded that early ACLR may be more beneficial to improve knee biomechanics during walking. [ABSTRACT FROM AUTHOR]

The aim of this review article is to appraise the design and functionality of above-knee prosthetic legs. So far, various transfemoral prosthetic legs are found to offer a stable gait to amputees but are limited to laboratories. The commercially available prosthetic legs are not reliable and comfortable enough to satisfy amputees. There is a dire need for creating a powered prosthetic knee joint that could address amputees' requirements. To pinpoint the gap in transfemoral prosthetic legs, prosthetic knee unit model designs, control frameworks, kinematics, and gait evaluations are concentrated. Ambulation exercises, ground-level walking, running, and slope walking are considered to help identify research gaps and areas where existing prostheses can be ameliorated. The results show that above-knee amputees can more effectively manage their issues with the aid of an active prosthesis, capable of reliable gait. To accomplish the necessary control, closed loop controllers and volitional control are integral parts. Future studies should consider designing a transfemoral electromechanical prosthesis based on electromyographic (EMG) signals to better predict the amputee's intent and control in accordance with that intent. [ABSTRACT FROM AUTHOR]

Abstract Background BASHTI is an implant-less anterior cruciate ligament (ACL) reconstruction technique, which resolves the problems caused by implants such as interference screws. This study aims to investigate the effect of the drill bit and tendon’s diameter on the Core Bone Engaged Length (CBEL) and the fixation strength. CBEL is the length of core bone which has a full engagement with both tunnel and graft at the same time. Methods 60 in-vitro tests were conducted for 6, 7, 8, and 9 mm tendon sizes with a 10 mm bone tunnel. In this study bovine tendons and dummy bone blocks were used to model the fixation. Drill bits were used to extract the core bone for securing the auto-graft. A three-stage tensile test including a force-controlled cyclical preloading of 10–50 N with a frequency of 0.1 Hz for 10 cycles, followed by the main force-controlled cyclical loading of 50–200 N with a frequency of 0.5 Hz for 150 cycles, and immediately a displacement-controlled single cycle pull-out load with a rate of 20 mm/min were carried out to discover the fixation strength of each sample. Results The 6 mm group had the greatest CBEL. However, all cases in this group failed in loadings below 200 N, which is the minimum required strength after ACL reconstruction. The fixation strength of cases with more than 200 N fixation strength for 7, 8, and 9 mm tendon diameters were 275 ± 42, 330 ± 110, and 348 ± 93 N, respectively, showing insignificant difference between groups (P-value = 0.45). Nevertheless, CBELs for these groups were 16.6 ± 3.4, 9.6 ± 2.4, and 11.7 ± 3.8 mm, respectively, implying a significant increase in CBEL in the 7 mm group than that for 8 and 9 mm groups (P-value = 0.002 and 0.049, respectively). Conclusion Results showed that CBEL could assess the quality of BASHTI technique. However, CBEL was an inverse function of tendon compression, so it was not an independent parameter to determine BASHTI strength. Also, the CBEL of 7 mm group which fulfilled the 200 N threshold was higher than that of 8 and 9 mm groups, so its healing process speed may be higher, which is recommended for a future study in this field.

Introduction: This work aimed to develop a novel multipurpose device for guided knee flexion-extension, both passively using a motorized pneumatic system and actively (muscle-driven) with the joint unloaded or loaded during dynamic MRI. Secondary objectives were to characterize the participant experience during device use, and present preliminary dynamic MRI data to demonstrate the different device capabilities. Material and methods: Self-reported outcomes were used to characterize the pain, physical exertion and discomfort levels experienced by 10 healthy male participants during four different active knee motion and loading protocols using the novel device. Knee angular data were recorded during the protocols to determine the maximum knee range of motion achievable. Dynamic MRI was acquired for three healthy volunteers during passive, unloaded knee motion using 2D Cartesian TSE, 2D radial GRE and 3D UTE sequences; and during active, unloaded and loaded knee motion using 2D radial GRE imaging. Because of the different MRI sequences used, spatial resolution was inherently lower for active knee motion than for passive motion acquisitions. Results: Depending on the protocol, some participants reported slight pain, mild discomfort and varying levels of physical exertion. On average, participants achieved ∼40° of knee flexion; loaded conditions can create knee moments up to 27 Nm. High quality imaging data were obtained during different motion and loading conditions. Dynamic 3D data allowed to retrospectively extract arbitrarily oriented slices. Conclusion: A novel multipurpose device for guided, physiologically relevant knee motion and loading during dynamic MRI was developed. Device use was well tolerated and suitable for acquiring high quality images during different motion and loading conditions. Different bone positions between loaded and unloaded conditions were likely due to out-of-plane motion, particularly because image registration was not performed. Ultimately, this device could be used to advance our understanding of physiological and pathological joint mechanics.

BACKGROUND: The quantitative recruitment of motor units depends on specific demands, including movement velocity. DNA microarrays differ according to sex, and these sex-related differences affect the fiber type composition. OBJECTIVE: The aim of this study is to demonstrate inter-sex differences in the isokinetic parameters, isokinetic phases, and muscle activities and to investigate the correlation between muscle activity and isokinetic data. METHODS: A total of 41 healthy adults (20 male, 21 female) performed concentric knee extension at angular velocities of 60 ∘ /s, 180 ∘ /s, and 240 ∘ /s. The outcome measures consisted of the isokinetic peak moment (PM), normalized PM (PM/BW), total work, and power, alongside the acceleration, iso-speed and deceleration, sub-phases. Muscle activity was recorded from the rectus femoris, vastus lateralis, and vastus medialis using surface EMG. RESULTS: There were significant two-factor main effect and interaction between sex and angular velocity on the power of knee extension and isokinetic phase (p < 0.05). As the velocity increased, the increase in power of males was greater than that of females. In contrast, with the increase in velocity, PM, PM/BW, and total work decreased, but no significant interaction was observed between velocity and sex. At high velocity, males showed higher acceleration ability than females. CONCLUSION: The sex-dependent responses to velocity were more affected by differences in total movement time than force production. Fast isokinetic exercise should consider the acceleration ability rather than the ability to produce force. [ABSTRACT FROM AUTHOR]

Anterior cruciate ligament (ACL) rupture is a very common knee joint injury. Torn ACLs are currently reconstructed using tendon autografts. However, half of the patients develop osteoarthritis (OA) within 10 to 14 years postoperatively. Proposedly, this is caused by altered knee kine(ma)tics originating from changes in graft mechanical properties during the in vivo remodeling response. Therefore, the main aim was to use subject-specific finite element knee models and investigate the influence of decreasing graft stiffness and/or increasing graft laxity on knee kine(ma)tics and cartilage loading. In this research, 4 subject-specific knee geometries were used, and the material properties of the ACL were altered to either match currently used grafts or mimic in vivo graft remodeling, i.e., decreasing graft stiffness and/or increasing graft laxity. The results confirm that the in vivo graft remodeling process increases the knee range of motion, up to >300 percent, and relocates the cartilage contact pressures, up to 4.3 mm. The effect of remodeling-induced graft mechanical properties on knee stability exceeded that of graft mechanical properties at the time of surgery. This indicates that altered mechanical properties of ACL grafts, caused by in vivo remodeling, can initiate the early onset of osteoarthritis, as observed in many patients clinically.

Context: Manual perturbation training improves knee functional performance and mitigates abnormal gait in patients with anterior cruciate ligament (ACL) rupture. However, manual perturbation training is time- and labor-intensive for therapists. Objective: To investigate whether perturbation training administered using a mechanical device can provide effects similar to manual training on clinical measures and knee biomechanics after ACL rupture. Design: Prospective cohort (therapeutic) study. A 2 x 2 analysis of variance was used for statistical analysis. Setting: A clinical and biomechanical laboratory. Patients: Eighteen level I/II patients with acute ACL ruptures participated in this preliminary study. Intervention: Nine patients received mechanical perturbation training on an automated mechanical device (mechanical group), and 9 patients received manual perturbation training (manual group). Outcome Measures: Patients completed performance-based testing (quadriceps strength and single-legged hop tests), patient-reported questionnaires (Knee Outcome Survey-Activities of Daily Living Scale, Global Rating Score, and International Knee Documentation Committee 2000), and 3-dimensional gait analysis before (pretesting) and after (post-testing) training. Results: There was no significant group-by-time interaction found for all measures (P ≥ .18). Main effects of time were found for International Knee Documentation Committee 2000 (pretesting: 69.10 [10.95], posttesting: 75.14 [7.19]), knee excursion during weight-acceptance (pretesting: 16.01° [3.99°]; posttesting: 17.28° [3.99°]) and midstance (pretesting: 14.78° [4.13°]; posttesting: 16.92° [4.53°]) and external knee-flexion moment (pretesting: 0.43 [0.11] N m/kg/m; posttesting: 0.48 [0.11] N m/kg/m) (P ≤ .04). After accounting for pretesting groups' differences, the mechanical group scored significantly higher on triple hops (mechanical: 96.73% [6.65%]; manual: 84.97% [6.83%]) and 6-m timed hops (mechanical: 102.07% [9.50%]; manual: 91.21 [9.42%]) (P ≤ .047) compared with manual group. CONCLUSION: The clinical significance of this study is the mechanical perturbation training produced effects similar to manual training, with both training methods were equally effective at improving patients' perception of knee function and increasing knee excursion and external flexion moment during walking after acute ACL rupture. Mechanical perturbation training is a potential treatment to improve patients' functional and biomechanical outcomes after ACL rupture. [ABSTRACT FROM AUTHOR]

Abstract Background The redislocation rate of conservatively treated patella instability is high. One of the leading surgical strategies is medial patellofemoral ligament reconstruction. Over-tensioning is one of the most challenging complications in static medial patellofemoral ligament reconstruction as the graft used for reconstruction is isometric and the anatomical MPFL is a mostly dynamic structure. As an alternative to established static reconstruction techniques, dynamic graft techniques have been introduced for stabilizing the patella with the aim of providing a more physiological reconstruction of the medial patellofemoral ligament. To date, data on clinical outcomes are scarce and on biomechanical outcomes of the dynamic MPFL reconstruction are lacking. Here, we present the protocol of a randomized clinical trial for comparing clinical and biomechanical outcomes of dynamic versus static medial patellofemoral ligament reconstruction. Methods This study is a prospective, single blinded, randomized, multicenter, multimodal (clinical and biomechanical) clinical trial. Patients with recurrent patella dislocation requiring isolated MPFL reconstruction will be recruited and randomized to the dynamic or static reconstruction technique. Participants will be followed up for 2 years with a total of five follow-ups. Preoperative magnetic resonance imaging, upright radiographs, surgical reports and patient records will be evaluated, and clinical and functional outcomes will be measured. Patient-reported knee function and anterior knee pain as assessed with the Kujala score will serve as primary outcome. For biomechanical outcome, pre- and postoperative evaluations will be performed to assess isokinetic muscle strength, gait asymmetry, joint kinematics and kinetics, and timing of muscle activity. Discussion The results of the study will clarify whether the reported surgery success for patella stabilization via dynamic MPFL reconstruction is due to muscle contraction or to the passive tenodesis effect combined with clinical outcome measures. With this study, we will provide much needed information on knee biomechanics after dynamic versus static MPFL reconstruction to provide evidence to support orthopedic surgeons in evidence-based decision-making in their quest for surgical techniques most favorable for their patients. Trial registration The study protocol was registered at clinicaltrials.gov (NCT04849130). Registered 19 April 2021, https://clinicaltrials.gov/ct2/show/NCT04849130 .

Injuries to the meniscus are common and can impair physical activities. Bioprinted meniscal tissue offers an attractive alternative to donor tissue for meniscal repair but achieving the strength of native tissue is a challenge. Here we report the development of a tissue engineering bioreactor designed to apply repetitive force which may lead to an increase in the compressive modulus and durability of bioprinted meniscal tissues. The modular bioreactor system is composed of a sterilizable tissue culture vessel together with a dock that applies and measures mechanical force. The culture vessel allows for simultaneous compression cycling of two anatomically sized menisci. Using a hybrid linear actuator with a stepper motor, the dock can apply up to 300 N of force at speeds up to 20 mm/s, corresponding to the upper limits of anatomical force and motion in the knee. An interchangeable 22 N load cell was mated between the culture vessel and the dock to log changes in force. Both the culture vessel and dock are maintained in a standard cell culture incubator to provide heat and CO2, while the dock is powered and controlled externally using a step motor drive and customized software.

Background: BASHTI is an implant-less anterior cruciate ligament (ACL) reconstruction technique, which resolves the problems caused by implants such as interference screws. This study aims to investigate the effect of the drill bit and tendon's diameter on the Core Bone Engaged Length (CBEL) and the fixation strength. CBEL is the length of core bone which has a full engagement with both tunnel and graft at the same time. Methods: 60 in-vitro tests were conducted for 6, 7, 8, and 9 mm tendon sizes with a 10 mm bone tunnel. In this study bovine tendons and dummy bone blocks were used to model the fixation. Drill bits were used to extract the core bone for securing the auto-graft. A three-stage tensile test including a force-controlled cyclical preloading of 10–50 N with a frequency of 0.1 Hz for 10 cycles, followed by the main force-controlled cyclical loading of 50–200 N with a frequency of 0.5 Hz for 150 cycles, and immediately a displacement-controlled single cycle pull-out load with a rate of 20 mm/min were carried out to discover the fixation strength of each sample. Results: The 6 mm group had the greatest CBEL. However, all cases in this group failed in loadings below 200 N, which is the minimum required strength after ACL reconstruction. The fixation strength of cases with more than 200 N fixation strength for 7, 8, and 9 mm tendon diameters were 275 ± 42, 330 ± 110, and 348 ± 93 N, respectively, showing insignificant difference between groups (P-value = 0.45). Nevertheless, CBELs for these groups were 16.6 ± 3.4, 9.6 ± 2.4, and 11.7 ± 3.8 mm, respectively, implying a significant increase in CBEL in the 7 mm group than that for 8 and 9 mm groups (P-value = 0.002 and 0.049, respectively). Conclusion: Results showed that CBEL could assess the quality of BASHTI technique. However, CBEL was an inverse function of tendon compression, so it was not an independent parameter to determine BASHTI strength. Also, the CBEL of 7 mm group which fulfilled the 200 N threshold was higher than that of 8 and 9 mm groups, so its healing process speed may be higher, which is recommended for a future study in this field. [ABSTRACT FROM AUTHOR]

Knee osteoarthritis patient phenotyping is relevant to developing targeted treatments and assessing the treatment efficacy of total knee arthroplasty (TKA). This study aimed to identify clusters among TKA candidates based on demographic and knee mechanic features during gait, and compare gait changes between clusters postoperatively. TKA patients underwent 3D gait analysis 1‐week pre (n = 134) and 1‐year post‐TKA (n = 105). Principal component analysis was applied to frontal and sagittal knee angle and moment waveforms, extracting major patterns of variability. Age, sex, body mass index, gait speed, and frontal and sagittal pre‐TKA angle and moment PC scores previously identified as relevant to TKA outcomes were standardized (mean = 0, SD = 1, [134 × 15]). Multidimensional scaling and machine learning‐based hierarchical clustering were applied. Final clusters were validated by examining intercluster differences pre‐TKA and gait feature changes (PostPCscore – PrePCscore) by k‐way Χ2 and ANOVA tests. Four TKA candidate phenotypes yielded optimum clustering metrics, interpreted as higher and lower functioning clusters that were predominantly male and female. Higher functioning clusters pre‐TKA (clusters 1 and 4) had more dynamic sagittal flexion moment (p < 0.001) and frontal plane adduction moment (p < 0.001) loading/un‐loading patterns during stance. Post‐TKA, higher functioning clusters demonstrated less knee mechanic improvements during gait (flexion angle p < 0.001; flexion moment p < 0.001). TKA candidates can be characterized by four clusters, predominately separated by sex and knee joint biomechanics. Post‐TKA knee kinematics and kinetics improvements were cluster‐specific; lower functioning clusters experienced more improvement. Cluster‐based patient profiling may aid in triaging and developing OA management and surgical strategies meeting group‐level function needs. [ABSTRACT FROM AUTHOR]

Background: Biomechanical markers including reductions in sagittal plane kinematics and moments, increases in knee adduction moments (KAM), and altered muscle activations have been identified as hallmark indicators of knee osteoarthritis (OA). However, it remains unknown whether these features of knee OA gait are exclusive to the diseased joint.Research Question: To determine whether specific gait outcomes previously linked to symptomatic medial compartment knee OA are unique to knee OA by concurrently investigating a group of asymptomatic individuals and those with hip OA.Methods: 16 individuals with moderate medial compartment knee OA, 16 individuals with moderate hip OA, and 16 asymptomatic controls were recruited. Participants walked on a treadmill while segment kinematics and ground reaction forces were recorded. Sagittal plane kinematics and sagittal and frontal plane moments were calculated. Surface electromyograms were recorded from lateral and medial hamstrings and gastrocnemius and vastus lateralis and medialis. Discrete variable analysis was used to investigate knee joint mechanics and muscle activation ratios. Analysis of Variance models using Bonferroni corrections determined between group differences (α = 0.0167).Results: Sagittal plane knee kinematics and moments were statistically similar among all groups (p > 0.0167). No differences were found for peak KAM and impulse between knee OA and asymptomatic groups (p > 0.0167) but peak KAM (p = 0.006 and impulse (p = 0.001) were greater in the knee OA group compared to hip OA. The hip OA group had a lower KAM impulse (p < 0.0167) compared to the knee OA and asymptomatic groups. A greater LH:MH activation ratio (p < 0.0167) was found in the knee OA group compared to hip OA and asymptomatic groups. No other activation ratio differences were found (p > 0.0167).Significance: Medial and lateral hamstring muscle activation levels may provide utility as a knee OA gait biomarker compared to biomechanical outcomes, quadriceps and gastrocnemius activation, when differentiating knee OA from asymptomatic and hip OA cohorts. [ABSTRACT FROM AUTHOR]

Almost 86 % of all tibial plateau fractures involves the failure of the postero-latero-central region of the tibial plateau. Surgical treatment of this region is technically demanding and in case of limited depression, it's occasionally chosen to leave them untreated. The aim of the study is to numerically check to what extent this choice can be accepted avoiding inferior outcomes (i.e. joint instability), and to analyze posterior soft tissues role in presence of this fractures. Starting from a previous validated finite element model with baseline structures, several configurations were developed by inserting posterior soft tissues and postero-latero-central fracture, with different articular depressions. Squat motion was numerically simulated and tibio-femoral kinematics were compared among configurations. An increasing step-off led to a progressive joint instability, especially in the first 35°-40° of flexion. Posterior soft tissues showed to be beneficial in initial stabilization and early flexion. Tibial Axial Rotation didn't show any restorative effect of posterior soft tissues on knee kinematics. Tibial Antero-Posterior Translation is the most significant biomechanical parameter, showing posterior soft tissues restoring native antero-posterior translation, completely for 1-mm step-off fracture, only partially for 2-mm step-off fracture, and not sufficiently for 3-mm step-off fracture, at least in the first 30° of flexion. The results suggest that postero-latero-central fractures with step-off ≥2 mm should be treated to restore articular kinematic, whereas fractures with step-off <2 mm need a broad evaluation to assess the effective need of surgery. These information can be valuable for surgeons, to aid their decision to surgically operate or not. • Depression increase leads to a progressive alteration of tibio-femoral kinematics. • 2-mm (or higher) depression should be treated to restore articular kinematic. • 1-mm (or lower) depression need a broad evaluation to assess the need of surgery. [ABSTRACT FROM AUTHOR]

Recent interest has uncovered the importance of understanding meniscal root anatomy, its effect on biomechanics of the knee joint, and appropriate treatment modalities. Meniscal root tears may account for up to one-fifth of all meniscal tears and have downstream consequences that can be as severe as total meniscectomy due to the unique force-dispersing properties of the meniscus. Meniscal biomechanics rely heavily upon the integrity of root attachments, and this historically overlooked etiology of knee pain and early onset osteoarthritis plays a vital role in maintaining the longevity of the knee joint. As meniscal root pathology becomes more commonly known and clinically assessed, an understanding of classifications, repair methods, and indications is important for surgeons.

The objective of this study was to examine the effects of subsensory noise and fatigue on knee biomechanics during the athletic task of landing followed by cross-over cutting. A total of 32 healthy male athletes participated in the study. They were evenly divided into 2 groups: no fatigue group and fatigue group. Fatigue was induced to the lower extremity by a repetitive squatting exercise in the fatigue group. Subsensory noise was generated by linear miniature vibrators bilaterally placed around the knee joints. During data collection, the participants were instructed to perform landing followed by cross-over cutting in both the subsensory on and off conditions. Dependent variables were selected to assess knee biomechanics in the phases of landing and cross-over cutting, separately. Results showed that fatigue resulted in larger knee flexion during landing and larger knee internal rotation during cross-over cutting. Subsensory noise was found to reduce knee rotation impulse during cross-over cutting. These findings suggest that cross-over cutting is more dangerous than landing in the fatigue condition, and subsensory noise may lead to changes in knee biomechanics consistent with reduced risk of anterior cruciate ligament injuries, but the changes may be task-specific. [ABSTRACT FROM AUTHOR]

Given the high rates of both primary and secondary anterior cruciate ligament (ACL) injuries in multidirectional field sports, there is a need to develop easily accessible methods for practitioners to monitor ACL injury risk. Field-based methods to assess knee variables associated with ACL injury are of particular interest to practitioners for monitoring injury risk in applied sports settings. Knee variables or proxy measures derived from wearable inertial measurement units (IMUs) may thus provide a powerful tool for efficient injury risk management. Therefore, the aim of this study was to identify whether there were correlations between laboratory-derived knee variables (knee range of motion (RoM), change in knee moment, and knee stiffness) and metrics derived from IMUs (angular velocities and accelerations) placed on the tibia and thigh, across a range of movements performed in practitioner assessments used to monitor ACL injury risk. Ground reaction forces, three-dimensional kinematics, and triaxial IMU data were recorded from nineteen healthy male participants performing bilateral and unilateral drop jumps, and a 90° cutting task. Spearman's correlations were used to examine the correlations between knee variables and IMU-derived metrics. A significant strong positive correlation was observed between knee RoM and the area under the tibia angular velocity curve in all movements. Significant strong correlations were also observed in the unilateral drop jump between knee RoM, change in knee moment, and knee stiffness, and the area under the tibia acceleration curve (rs = 0.776, rs = −0.712, and rs = −0.765, respectively). A significant moderate correlation was observed between both knee RoM and knee stiffness, and the area under the thigh angular velocity curve (rs = 0.682 and rs = −0.641, respectively). The findings from this study suggest that it may be feasible to use IMU-derived angular velocities and acceleration measurements as proxy measures of knee variables in movements included in practitioner assessments used to monitor ACL injury risk. [ABSTRACT FROM AUTHOR]

Background Although dynamic knee valgus can be visually identified using the 2D frontal plane projection angle (FPPA), the validity of the FPPA in terms of predicting frontal plane knee kinematics has been questioned. The biomechanical utility of the FPPA may lie in its ability to predict frontal plane knee moments. Hypothesis/Purpose The purpose of the current study was to comprehensively evaluate the ability of the FPPA to predict the frontal plane knee kinetics (peak moment, average moment, and moment at peak knee flexion) across a wide range of tasks (stepping, landing, and change of direction). Design Crossover Study Design. Methods Three-dimensional lower-extremity kinetics and 2D video were obtained from 39 healthy athletes (15 males and 24 females) during execution of six tasks (step down, drop jump, lateral shuffle, deceleration, triple hop, side-step-cut). Linear regression analysis was performed to determine if the 2D FPPA at peak knee flexion predicted frontal plane knee moment variables during the deceleration phase of each task (peak moment, average moment, moment at peak knee flexion). Results The FPPA was found to significantly predict the peak frontal plane knee moment for two tasks (deceleration and side-step-cut, R² = 12% to 25%), average frontal plane knee moment for five tasks (drop jump, shuffle, deceleration, triple hop, side-step-cut, R² = 15% to 40%), and frontal plane knee moment at peak knee flexion for five tasks (drop jump, shuffle, deceleration, triple hop, side-step-cut, R² = 16% to 45%). Conclusion An increased FPPA (medial knee collapse) predicted increased knee valgus moments (or decreased knee varus moments) during landing and change of direction tasks (but not stepping). However, the predictive ability of the FPPA was weak to moderate. [ABSTRACT FROM AUTHOR]

This work aimed to develop a novel multipurpose device for guided knee flexion-extension, both passively using a motorized pneumatic system and actively (muscle-driven) with the joint unloaded or loaded during dynamic MRI. Secondary objectives were to characterize the participant experience during device use, and present preliminary dynamic MRI data to demonstrate the different device capabilities. Self-reported outcomes were used to characterize the pain, physical exertion and discomfort levels experienced by 10 healthy male participants during four different active knee motion and loading protocols using the novel device. Knee angular data were recorded during the protocols to determine the maximum knee range of motion achievable. Dynamic MRI was acquired for three healthy volunteers during passive, unloaded knee motion using 2D Cartesian TSE, 2D radial GRE and 3D UTE sequences; and during active, unloaded and loaded knee motion using 2D radial GRE imaging. Because of the different MRI sequences used, spatial resolution was inherently lower for active knee motion than for passive motion acquisitions. Depending on the protocol, some participants reported slight pain, mild discomfort and varying levels of physical exertion. On average, participants achieved ∼40° of knee flexion; loaded conditions can create knee moments up to 27 Nm. High quality imaging data were obtained during different motion and loading conditions. Dynamic 3D data allowed to retrospectively extract arbitrarily oriented slices. A novel multipurpose device for guided, physiologically relevant knee motion and loading during dynamic MRI was developed. Device use was well tolerated and suitable for acquiring high quality images during different motion and loading conditions. Different bone positions between loaded and unloaded conditions were likely due to out-of-plane motion, particularly because image registration was not performed. Ultimately, this device could be used to advance our understanding of physiological and pathological joint mechanics. [ABSTRACT FROM AUTHOR]

Every year in Europe more than 500 thousand injuries that involve the anterior cruciate ligament (ACL) are diagnosed. The ACL is one of the main restraints within the human knee, focused on stabilizing the joint and controlling the relative movement between the tibia and femur under mechanical stress (i.e., laxity). Ligament laxity measurement is clinically valuable for diagnosing ACL injury and comparing possible outcomes of surgical procedures. In general, knee laxity assessment is manually performed and provides information to clinicians which is mainly subjective. Only recently quantitative assessment of knee laxity through instrumental approaches has been introduced and become a fundamental asset in clinical practice. However, the current solutions provide only partial information about either static or dynamic laxity. To support a multiparametric approach using a single device, an innovative smart knee brace for knee laxity evaluation was developed. Equipped with stretchable strain sensors and inertial measurement units (IMUs), the wearable system was designed to provide quantitative information concerning the drawer, Lachman, and pivot shift tests. We specifically characterized IMUs by using a reference sensor. Applying the Bland–Altman method, the limit of agreement was found to be less than 0.06 m/s2 for the accelerometer, 0.06 rad/s for the gyroscope and 0.08 μT for the magnetometer. By using an appropriate characterizing setup, the average gauge factor of the three strain sensors was 2.169. Finally, we realized a pilot study to compare the outcomes with a marker-based optoelectronic stereophotogrammetric system to verify the validity of the designed system. The preliminary findings for the capability of the system to discriminate possible ACL lesions are encouraging; in fact, the smart brace could be an effective support for an objective and quantitative diagnosis of ACL tear by supporting the simultaneous assessment of both rotational and translational laxity. To obtain reliable information about the real effectiveness of the system, further clinical validation is necessary. [ABSTRACT FROM AUTHOR]

Background: The redislocation rate of conservatively treated patella instability is high. One of the leading surgical strategies is medial patellofemoral ligament reconstruction. Over-tensioning is one of the most challenging complications in static medial patellofemoral ligament reconstruction as the graft used for reconstruction is isometric and the anatomical MPFL is a mostly dynamic structure. As an alternative to established static reconstruction techniques, dynamic graft techniques have been introduced for stabilizing the patella with the aim of providing a more physiological reconstruction of the medial patellofemoral ligament. To date, data on clinical outcomes are scarce and on biomechanical outcomes of the dynamic MPFL reconstruction are lacking. Here, we present the protocol of a randomized clinical trial for comparing clinical and biomechanical outcomes of dynamic versus static medial patellofemoral ligament reconstruction. Methods: This study is a prospective, single blinded, randomized, multicenter, multimodal (clinical and biomechanical) clinical trial. Patients with recurrent patella dislocation requiring isolated MPFL reconstruction will be recruited and randomized to the dynamic or static reconstruction technique. Participants will be followed up for 2 years with a total of five follow-ups. Preoperative magnetic resonance imaging, upright radiographs, surgical reports and patient records will be evaluated, and clinical and functional outcomes will be measured. Patient-reported knee function and anterior knee pain as assessed with the Kujala score will serve as primary outcome. For biomechanical outcome, pre- and postoperative evaluations will be performed to assess isokinetic muscle strength, gait asymmetry, joint kinematics and kinetics, and timing of muscle activity. Discussion: The results of the study will clarify whether the reported surgery success for patella stabilization via dynamic MPFL reconstruction is due to muscle contraction or to the passive tenodesis effect combined with clinical outcome measures. With this study, we will provide much needed information on knee biomechanics after dynamic versus static MPFL reconstruction to provide evidence to support orthopedic surgeons in evidence-based decision-making in their quest for surgical techniques most favorable for their patients. Trial registration The study protocol was registered at clinicaltrials.gov (NCT04849130). Registered 19 April 2021, https://clinicaltrials.gov/ct2/show/NCT04849130. [ABSTRACT FROM AUTHOR]

Context: Excessive knee valgus and tibial external rotation relative to the femur during weight bearing motions, such as jump-landing, reportedly increases the risk of developing chronic knee pain, such as patellofemoral pain. Excessive deviations from normal ranges of several static lower extremity alignment measures and dynamic hip motions may also increase the risks for patellofemoral pain. Objective: To determine the relationship between lower extremity alignments and hip motions to frontal and transverse plane knee motions during double-leg landings. Design: Correlational study. Setting: Laboratory. Patients or Other Participants: 69 healthy, competitive athletes (27 men, 42 women; height, 166.5 ± 9.5 cm; weight, 61.3 ± 9.9 kg; age, 20.7 ± 1.0 y) participated in this study. Interventions: Prone and supine hip version, quadriceps angle, and tibiofemoral angle were measured. Frontal and transverse knee and hip angles at peak knee extensor moment during landing were calculated. Main Outcome Measures: 2 separate stepwise multiple regression analyses were conducted to predict frontal and transverse plane knee motions using 4 static lower extremity alignment measures and hip motions. Results: Greater hip adduction and prone hip anteversion, and lesser hip internal rotation and supine hip anteversion, were related to greater knee valgus motions (R2 = .475, P < .01). Greater hip adduction was related to greater knee external rotation (R² = .205, P < .01). Conclusions: Some targeted static lower extremity alignments and hip motions are associated with frontal and transverse knee motions. However, stronger relationships of hip motions with knee motions than static lower extremity alignments provided evidence that improving hip movements may help improve patellofemoral pain in those with lower extremity malalignments. [ABSTRACT FROM AUTHOR]

Purpose: The present study tested and compared the biomechanical properties of four different triplicate graft tendon techniques. Methods: 32 tripled tendons from the common extensor muscle of bovine fingers were tested on a material testing machine, passing the end loop over a metal rod of a clevis connected to the load cell on the upper side, and fixing the lower end to a clamp. The samples were divided into four groups: (A) tripled with a free end sutured only to one of the two fixed bundles (B) tripled with a free end positioned between the two fixed strands and sutured to both (C) tripled with an S-shape and all the three strands sutured together at the upper and lower extremities of the graft (D) partially quadrupled with the free end sutured together with the other three bundles at the upper extremity. Each sample was pretensioned at 50 N for 10 min and then subjected to 1000 load control cycles between 50 and 250 N. Finally, each sample was subjected to a load to failure test. Authors also present some preliminary results on the feasibility of a non-contact and full-field Thermoelastic Stress Analysis technique, based on Infrared Thermography, to evaluate the level of stress on the whole graft, and hence on each strand, during fatigue loading. Results: Eighty five percent of the samples failed at the level of the clamp. The cyclical elongation progressively decreased in all the samples and there was a simultaneous increase in stiffness. An increased stiffness was noted between Group 2 vs Group 3 and Group 2 vs Group 4 at the 500th and 1000th cycle. The failure loads were as follows: (a) 569.10 N, (b) 632.28 N, (c) 571.68 N, (d) 616.95 N. None of the parameters showed a statistically significant difference between the four groups. Conclusion: This study reported similar biomechanical behavior of four different models of tripled grafts suitable for ACL reconstruction. In addition, the biomechanics of overall tripled tendon grafts seems more affected by the viscoelastic property of the tendon itself rather than the preparation method. [ABSTRACT FROM AUTHOR]

Objective: Osteoarthritis (OA) is a multifactorial musculoskeletal disorder affecting mostly weight-bearing joints. Chondrocyte response to load is modulated by inflammatory mediators and factors involved in extracellular cartilage matrix (ECM) maintenance, but regulatory mechanisms are not fully clarified yet. By using a recently proposed experimental model combining biomechanical data with cartilage molecular information, basally and following ex-vivo load application, we aimed at improving the understanding of human cartilage response to cyclic mechanical compressive stimuli by including cartilage original anatomical position and OA degree as independent factors.Methods: 19 mono-compartmental Knee OA patients undergoing total knee replacement were recruited. Cartilage explants from four different femoral condyles zones and with different degeneration levels were collected. The response of cartilage samples, pooled according to OA score and anatomical position was tested ex-vivo in a bioreactor. Mechanical stimulation was obtained via a 3-MPa 1-Hz sinusoidal compressive load for 45-min to replicate average knee loading during normal walking. Samples were analysed for chondrocyte gene expression and ECM factor release.Results: Non parametric univariate and multivariate (generalized linear mixed model) analysis was performed to evaluate the effect of compression and IL-1β stimulation in relationship to the anatomical position, local disease severity and clinical parameters with a level of significance set at 0.05. We observed an anti-inflammatory effect of compression inducing a significant downmodulation of IL-6 and IL-8 levels correlated to the anatomical regions, but not to OA score. Moreover, ADAMTS5, PIICP, COMP and CS were upregulated by compression, whereas COL-2CAV was downmodulated, all in relationship to the anatomical position and to the OA degree.Conclusion: While unconfined compression testing may not be fully representative of the in-vivo biomechanical situation, this study demonstrates the importance to consider the original cartilage anatomical position for a reliable biomolecular analysis of knee OA metabolism following mechanical stimulation.