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Predictors of rebound after correction of coronal plane deformities using temporary hemiepiphysiodesis (TH) are not well defined. The following research questions were tested: (1) Is the dynamic knee joint load useful to improve rebound prediction accuracy? (2) Does a large initial deformity play a critical role in rebound development? (3) Are BMI and a young age risk factors for rebound? Fifty children and adolescents with idiopathic knee valgus malalignment were included. A deviation of the mechanical femorotibial angle (MFA) of ≥ 3° into valgus between explantation and the one-year follow-up period was chosen to classify a rebound. A rebound was detected in 22 of the 50 patients (44%). Two predictors of rebound were identified: 1. reduced peak lateral knee joint contact force in the first half of the stance phase at the time of explantation (72.7% prediction); 2. minor initial deformity according to the MFA (70.5% prediction). The best prediction (75%) was obtained by including both parameters in the binary logistic regression method. A TH should not be advised in patients with a minor initial deformity of the leg axis. Dynamic knee joint loading using gait analysis and musculoskeletal modeling can be used to determine the optimum time to remove the plates.

The AMTI VIVO™ six degree of freedom joint simulator allows reproducible preclinical testing of joint endoprostheses under specific kinematic and loading conditions. When testing total knee endoprosthesis, the articulating femoral and tibial components are each mounted on an actuator with two and four degrees of freedom, respectively. To approximate realistic physiological conditions with respect to soft tissues, the joint simulator features an integrated virtual ligament model that calculates the restoring forces of the ligament apparatus to be applied by the actuators. During joint motion, the locations of the ligament insertion points are calculated depending on both actuators’ coordinates. In the present study, we demonstrate that unintended elastic deformations of the actuators due to the specifically high contact forces in the artificial knee joint have a considerable impact on the calculated ligament forces. This study aims to investigate the effect of this structural compliance on experimental results. While the built-in algorithm for calculating the ligament forces cannot be altered by the user, a reduction of the ligament force deviations due to the elastic deformations could be achieved by preloading the articulating implant components in the reference configuration. As a proof of concept, a knee flexion motion with varying ligament conditions was simulated on the VIVO simulator and compared to data derived from a musculoskeletal multibody model of a total knee endoprosthesis.

While the FIFA 11 + Referees program (the 11 + Referees) is the only structured injury prevention program for referees, its effects on injury-related risk factors among referees remain underexplored. This study investigated the effects of the 11 + Referees on knee joint proprioception and dynamic balance. Thirty four female referees from the Tehran Premier Futsal League voluntarily participated and were randomly assigned to either a control group ( n  = 17) or the 11 + Referees group ( n  = 17). All participants underwent a baseline assessment including knee joint proprioception at angular velocities of 15°/s, 45°/s, and 60°/s, and position sense, as well as dynamic balance. Subsequently, the intervention group performed the 11 + Referees program three times weekly for 8 weeks, while the control group performed general warm-ups. Post-intervention, the same test battery was administered, and changes were analyzed to identify the program’s effects on the measures understudied. Significant improvements were observed in knee joint proprioception at 15°/s (F = 18.19, p  < 0.001, η²=0.44), 45°/s (F = 4.07, p  = 0.056, ηp²=0.15), and 60°/s (F = 6.63, p  = 0.017, η²=0.22) in the intervention group. However, dynamic balance did not show significant improvement (F = 0.79, p  = 0.38, η²=0.033). In conclusion, an eight-week application of the 11 + Referees enhanced knee joint proprioception in female referees with large effect sizes, but had no significant effect on dynamic balance. Improvements in proprioception may be attributed to neuromuscular adaptations resulting from regular program use. The absence of balance improvement could be due to the short intervention period and the hard futsal court surface, which may limit the effectiveness of certain balance exercises. Future studies should explore the program's effects on other injury risk factors and injury rates.

Static radiographic alignment fails to capture the dynamic nature of joint behaviour during functional tasks. To address this, our study evaluated the relationship between Hip-Knee-Ankle angle (HKAA) and dynamic biomechanical variables (dynamic HKAA (dHKAA), via projection of hip, knee, and ankle joint centers onto the frontal plane, knee adduction moment (KAM), and knee abduction angle (KAA)), during gait and sit-to-stand tasks with and without arm assistance. A further objective was to examine the mediolateral center of pressure (COP ML) as a complementary parameter for assessing joint loading and frontal plane alignment. Twenty-two patients (mean age 67 ± 9 years, BMI 28.7 ± 3.4 kg/m2) with end-stage knee osteoarthritis scheduled for total knee arthroplasty were recruited. HKAA was extracted from full-length standing radiographs, while dynamic variables from 3D motion capture and force plates data. Associations between static and dynamic parameters were evaluated using correlation and linear regression analyses. dHKAA consistently exhibited stronger correlations with KAM and KAA than radiographic HKAA, particularly during gait loading response (ρ = 0.93; R2 = 0.84, p < 0.01). Similar trends were observed in the other tasks, where HKAA showed limited associations. COP ML showed moderate correlations with KAM but none with dHKAA. These findings suggest that HKAA alone may not reliably capture functional joint loading, and that dHKAA provides a more comprehensive assessment of frontal plane knee behaviour. COP ML showed limited associations and should be cautiously interpreted in this context. These findings may enhance clinical assessments, surgical planning, and advancing-personalized, biomechanically driven intervention research.

Diverse marker sets and validation techniques have previously been utilized, posing challenges in comparing studies when assessing soft tissue artefacts in knee joint kinematics from motion analysis. This study aimed to analyse the data obtained from three different marker sets with the results derived from radiostereometric analysis (RSA) in measuring angular movements of the knee joint. Twelve post-knee replacement participants performed a one-leg step-down movement. Knee joint angular movements were analysed in flexion–extension, adduction-abduction, and internal-external rotation across all marker sets. The results were subsequently compared with those obtained from the RSA system using simple linear regression, a linear mixed-effects model, mean values and mean differences. All marker sets were found to systematically underestimate flexion–extension compared to RSA, with differences intensifying at higher knee flexion angles. The mean differences in the sagittal plane between RSA and the IOR marker set, progressively increased from approximately 5° (95% CI 4.3–4.9) to 15° (95% CI 11.6–17.9), reaching a maximum difference of 20° (95% CI 13.8–25.7) at 40° of knee flexion. Transverse and frontal plane data from all marker sets exhibited erratic errors compared to RSA. In summary, knee flexion–extension motions were consistent between marker sets, indicating minimal impact on results based on the marker set choice. However, all marker sets systematically underestimated skeletal motions in knee flexion–extension compared to RSA measurements. Data from the transverse and frontal planes were too inconsistent and therefore not reliable for use.

The hip-knee-ankle (HKA) angle is essential to assess surgical evaluation and disease progression in patients with knee osteoarthritis (KOA). Rapid, radiation-free assessment methods are a key area of research. This study investigates the reliability and validity of OpenPose, video-based human pose estimation method, for determining the HKA angle in KOA patients. In this study, we analyzed 50 knees affected by osteoarthritis. The HKA angle was measured using the pose estimation method and X-ray imaging before total knee arthroplasty. The pose estimation method demonstrated excellent test-retest reliability (ICC 1,1 = 1.000) and good consistency with radiography (ICC 2,1 = 0.897), with linear regression analysis showing a good correlation (R 2  = 0.814). Compared with radiography, the pose estimation method exhibited a fixed error of 0.131°. This is the first study to examine the feasibility of measuring the HKA angle from frontal-view videos of patients walking normally by using the pose estimation method. Using the pose estimation method to measure the HKA angle in knee osteoarthritis patients is reliable and valid. The pose estimation method provides a safe, cost-effective, and user-friendly solution for monitoring lower limb alignment, with promising applications in remote healthcare and rehabilitation management. It eliminates radiation exposure, avoiding the health risks associated with X-ray imaging, and it does not require specialized medical equipment, enabling fully automated analysis.

Purpose To evaluate if there was a correlation between in vivo kinematics of a medial-stabilized (MS) total knee arthroplasty (TKA) and post-operative clinical scores. We hypothesized that (1) a MS-TKA would produce a medial pivot movement and that (2) this specific pattern would be correlated with higher clinical scores. Methods 18 patients were evaluated through clinical and functional scores evaluation (Knee Society Score clinical and functional, Womac, Oxford), and kinematically through dynamic radiostereometric analysis (RSA) at 9 months after MS-TKA, during the execution of a sit-to-stand and a lunge motor task. The anteroposterior (AP) Low Point translation of medial and lateral femoral compartments was compared through Student’s t test ( p  < 0.05). A correlation analysis between scores and kinematics was performed through the Pearson’s correlation coefficient r . Results A significantly greater ( p  < 0.0001) anterior translation of the lateral compartment with respect to the medial one was found in both sit-to-stand (medial 2.9 mm ± 0.7 mm, lateral 7.1 mm ± 0.6 mm) and lunge (medial 5.3 mm ± 0.9 mm, lateral 10.9 mm ± 0.7 mm) motor tasks, thus resulting in a medial pivot pattern in about 70% of patients. Significant positive correlation in sit-to-stand was found between the peak of AP translation in the lateral compartment and clinical scores ( r  = 0.59 for Knee Society Score clinical and r  = 0.61 for Oxford). Moreover, we found that the higher peak of AP translation of the medial compartment correlated with lower clinical scores ( r  = − 0.55 for Knee Society Score clinical, r  = − 0.61 for Womac and r  = − 0.53 for Oxford) in the lunge. A negative correlation was found between Knee Society Score clinical and VV laxity during sit-to-stand ( r  = − 0.56) and peak of external rotation in the lunge motor task ( r  = − 0.66). Conclusions The MS-TKA investigated produced in vivo a medial pivot movement in about 70% of patients in both examined motor tasks. There was a correlation between the presence of medial pivot and higher post-operative scores. Level of evidence IV.

In vitro pre-clinical testing of total knee replacement (TKR) devices is a necessary step in the evaluation of new implant designs. Whole joint knee simulators, like the Kansas knee simulator (KKS), provide a controlled and repeatable loading environment for comparative evaluation of component designs or surgical alignment under dynamic conditions. Experimental testing, however, is time and cost prohibitive for design-phase evaluation of tens or hundreds of design variations. Experimentally-verified computational models provide an efficient platform for analysis of multiple components, sizes, and alignment conditions. The purpose of the current study was to develop and verify a computational model of a dynamic, whole joint knee simulator. Experimental internal–external and valgus–varus laxity tests, followed by dynamic deep knee bend and gait simulations in the KKS were performed on three cadaveric specimens. Specimen-specific finite element (FE) models of posterior-stabilized TKR were created from magnetic resonance images and CAD geometry. The laxity data was used to optimize mechanical properties of tibiofemoral soft-tissue structures on a specimen-specific basis. Each specimen was subsequently analyzed in a computational model of the experimental KKS, simulating both dynamic activities. The computational model represented all joints and actuators in the experimental setup, including a proportional-integral-derivative (PID) controller to drive quadriceps actuation. The computational model was verified against six degree-of-freedom patellofemoral (PF) and tibiofemoral (TF) kinematics and actuator loading during both deep knee bend and gait activities, with good agreement in trends and magnitudes between model predictions and experimental kinematics; differences were less than 1.8mm and 2.2° for PF and TF translations and rotations. The whole joint FE simulator described in this study can be applied to investigate a wide range of clinical and research questions.

Purpose Osteoarthritis of knees with varus deformity is associated with a compensatory valgus deformity of the hindfoot and a lateral loading foot pressure pattern. However, whether this abnormal loading pattern is corrected in total knee arthroplasty (TKA) is unclear. Methods The alignment and loading pattern of 91 consecutive patients (121 knees) undergoing TKA with pre-operative varus more than 10° were evaluated prospectively with functional outcome scores, static conventional radiography and dynamic pedobarogaphy pre-operatively and 1-year post-operatively. Outcomes assessed were Oxford Knee Scores, American Orthopaedic Foot and Ankle Scores, femorotibial mechanical angle, tibia–hindfoot angle, hindfoot valgus/varus index (VVI), foot line of pressure (LOP) laterality and peak pressure (PP) at both time points. Results Of 121 knees, 98 (81%) regained normal alignment of the knee and 114 (92%) of the hindfoot. Similarly, PP ( p  < 0.001), VVI (pre-operative: − 0.29 ± 0.22, post-operative: − 0.04 ± 0.23, p  < 0.001) and LOP laterality (pre-operative: 7% medial, post-operative: 96% medial, p  < 0.001) all medialised post-operatively. All patients had improved functional outcomes at the knee (pre-operative: 20 ± 2, post-operative: 40 ± 2, p  < 0.001) and ankle (pre-operative: 59 ± 10, post-operative: 89 ± 6, p  < 0.001). Conclusion The present study shows, following the correction of knee varus with TKA, hindfoot alignment and foot loading pattern are both restored in the majority of patients. TKA offers both static and dynamic correction as seen in the hindfoot and loading pattern, respectively. Level of evidence Level III: prospective case–control study.

Total knee arthroplasty (TKA) is aimed mainly at reducing pain and restoring mobility. However, mobility deficits can persist even longer than 1 year. The trunk function and movement velocity of any region have been recently recognized to be critical for determining mobility in older people. Therefore, the main goal of this quasi-randomized trial is to clarify the effectiveness of a novel training method, the seated side tapping (SST) training, for improving mobility by focusing on movement velocity of trunk function in the short term after TKA. SST training consists of side trunk movements repeated as quickly as possible in a seated position. All participants after TKA were randomly assigned to the SST training group (n = 37) or control training group (n = 38). The participants in the SST group performed SST training plus the standard rehabilitation program 5 days per week for 3 weeks after TKA, while the control group performed only the standard rehabilitation programs. The primary outcome was the effect of SST training on mobility, indicated by gait speed and the timed up and go test (TUG) time. Measurements were performed before and 1, 2, and 3 weeks after surgery. At all-time points, the patients in the SST group showed significantly better mobility, despite that knee function, represented by muscle strength, range of motion, and degree of pain at the knee joint, was similar in both groups. The difference in gait speed between the groups was >0.1 m/s at all time points, which is clinically significant. SST training significantly improved patients' mobility within 3 weeks after TKA, despite that no additional benefit was observed in knee function. The findings in this study indicate that SST training may be considered as a part of the rehabilitation program after TKA, although further evaluation of its long-term effectiveness is needed. University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR; UMIN000027909).