Mobile bearing shows larger rollback motion than fixed bearing in total knee arthroplasty using a medial stabilising technique with a navigation system.

Purpose: This study aimed to investigate the intraoperative knee kinematics of cruciate-retaining total knee arthroplasty with a medial stabilising technique (MST-TKA) and compare the kinematics between mobile- and fixed-bearing MST-TKAs. We hypothesised that mobile-bearing MST-TKA would result in greater physiological kinematic motion than fixed-bearing MST-TKA. Methods: Twenty-one and 20 knees underwent mobile- and fixed-bearing MST-TKAs using a navigation system (Orthopilot® ver. 6.0; B. Braun Aesculap), respectively. In the preoperative and postoperative kinematic analysis, the knee was moved manually from 0° to 120°, and femoral anteroposterior translations of the medial femoral condyle (MFC) and lateral femoral condyle (LFC) were recorded every 0.1 s from 0° to 120°. Data were subsequently extracted from the software every 10° of flexion and compared between the two groups, and the correlation coefficients between preoperative and postoperative kinematics were calculated. Results: In the postoperative analysis, the MFC in the mobile-bearing group showed significant posterior translation at 100°, 110° and 120° compared to the fixed-bearing group (p < 0.01). Similarly, the LFC in the mobile-bearing group showed significant posterior translation at 100°, 110° and 120° compared to the fixed-bearing group (p < 0.05, p < 0.01 and p < 0.05, respectively). In the mobile-bearing group, the preoperative and postoperative anteroposterior translations of the MFC and LFC were correlated (p < 0.01), while in the fixed-bearing group, there was no correlation. Conclusion: The femoral rollback motion in the mobile-bearing MST-TKA correlated with the preoperative kinematics and was larger than that in the fixed-bearing group. Level of Evidence: Level II, therapeutic prospective cohort study.

Can We Target Close Therapeutic Goals in the Gait Re-Education Algorithm for Stroke Patients at the Beginning of the Rehabilitation Process?

(1) Background: The study aimed to determine the most important activities of the knee joints related to gait re-education in patients in the subacute period after a stroke. We focused on the tests that a physiotherapist could perform in daily clinical practice. (2) Methods: Twenty-nine stroke patients (SG) and 29 healthy volunteers (CG) were included in the study. The patients underwent the 5-meter walk test (5mWT) and the Timed Up and Go test (TUG). Tests such as step up, step down, squat, step forward, and joint position sense test (JPS) were also performed, and the subjects were assessed using wireless motion sensors. (3) Results: We observed significant differences in the time needed to complete the 5mWT and TUG tests between groups. The results obtained in the JPS show a significant difference between the paretic and the non-paretic limbs compared to the CG group. A significantly smaller range of knee joint flexion (ROM) was observed in the paretic limb compared to the non-paretic and control limbs in the step down test and between the paretic and non-paretic limbs in the step forward test. (4) Conclusions: The described functional tests are useful in assessing a stroke patient's motor skills and can be performed in daily clinical practice.

Chronic ACLD Knees with Early Developmental Cartilage Lesions Exhibited Increased Posterior Tibial Translation during Level Walking.

OBJECTIVE: Early articular cartilage lesion (CL) is a vital sign in the onset of posttraumatic knee osteoarthritis (PTOA) in patients with anterior cruciate ligament deficiency (ACLD). Researchers have suggested that altered kinematics could accelerate CLs and, therefore, lead to the onset of PTOA. However, little is known about whether specific knee kinematics exist that lead to early CL in chronic ACLD knees. Level walking is the most frequent and relevant in vivo activity, which greatly impacts knee health. We hypothesized that the knee kinematics during level walking in chronic ACLD knees with early tibiofemoral CL would significantly differ from those of chronic ACLD knees without early tibiofemoral CL. METHODS: Thirty patients with a chronic ACLD history, including 18 subjects with CLs and 12 subjects without CLs, and 35 healthy control subjects were recruited for the study from July 2020 to August 2022. The knee kinematic data during level walking were collected using a three-dimensional motion analysis system. The kinematic differences between groups were compared using statistical parametric mapping with one dimension for One-Way ANOVA. The cartilage statuses of the ACLD knees were assessed via MRI examination. The CLs distribution of subjects was evaluated using a modified Noyes scale and analyzed by chi-square tests. RESULTS: ACLD knees with CLs had significantly greater posterior tibial translation (7.7-8.0mm, 12%-18% gait cycle GC, p = 0.014) compared to ACLD knees without CLs during level walking. ACLD knees with CLs had greater posterior tibial translation (4.6-5.5mm, 0%-23% GC, p < 0.001; 5.8-8.0mm, 86%-100% GC, p < 0.001) than healthy controls during level walking. In the group of ACLD knees with CLs, CL is mainly located in the back of the tibia plateau and front of load bearing area of the medial femoral condyle (p < 0.05). CONCLUSION: Chronic anterior cruciate ligament deficient knees with cartilage lesions have increased posterior tibial translation compared to anterior cruciate ligament deficient knees without cartilage lesions and healthy subjects. The posterior tibial translation may play an important role in knee cartilage degeneration in ACLD knees. The increased posterior tibial translation and cartilage lesion characteristics may improve our understanding of the role of knee kinematics in cartilage degeneration and could be a helpful potential reference for anterior cruciate ligament deficient therapy, such as physical training to improve abnormal kinematic behavior.

Comparing novel smartphone pose estimation frameworks with the Kinect V2 for knee tracking during athletic stress tests.

PURPOSE: To compare the accuracy of the Microsoft Kinect V2 with novel pose estimation frameworks, in assessing knee kinematics during athletic stress tests, for fast and portable risk assessment of anterior cruciate ligament (ACL) injury. METHODS: We captured 254 varsity athletes, using the Kinect V2 and a smartphone application utilizing Google's MediaPipe framework. The devices were placed as close as possible and used to capture a person, facing the cameras, performing one of three athletic stress tests at a distance of 2.5 ms. Custom software translated the results from both frameworks to the same format. We then extracted relevant knee angles at key moments of the jump and compared them, using the Kinect V2 as the ground truth. RESULTS: The results show relatively small angle differences between the two solutions in the coronal plane and moderate angle differences on the sagittal plane. Overall, the MediaPipe framework results seem to underestimate both knee valgus angles and knee sagittal angles compared to the Kinect V2. CONCLUSION: This preliminary study demonstrates the potential for Google's MediaPipe framework to be used for calculating lower limb kinematics during athletic stress test motions, which can run on most modern smartphones, as it produces similar results to the Kinect V2. A smartphone application similar to the one developed could potentially be used for low cost and widespread ACL injury prevention.

The Difference in the Assessment of Knee Extension/Flexion Angles during Gait between Two Calibration Methods for Wearable Goniometer Sensors.

Frontal and axial knee motion can affect the accuracy of the knee extension/flexion motion measurement using a wearable goniometer. The purpose of this study was to test the hypothesis that calibrating the goniometer on an individual's body would reduce errors in knee flexion angle during gait, compared to bench calibration. Ten young adults (23.2 ± 1.3 years) were enrolled. Knee flexion angles during gait were simultaneously assessed using a wearable goniometer sensor and an optical three-dimensional motion analysis system, and the absolute error (AE) between the two methods was calculated. The mean AE across a gait cycle was 2.4° (0.5°) for the on-body calibration, and the AE was acceptable (<5°) throughout a gait cycle (range: 1.5-3.8°). The mean AE for the on-bench calibration was 4.9° (3.4°) (range: 1.9-13.6°). Statistical parametric mapping (SPM) analysis revealed that the AE of the on-body calibration was significantly smaller than that of the on-bench calibration during 67-82% of the gait cycle. The results indicated that the on-body calibration of a goniometer sensor had acceptable and better validity compared to the on-bench calibration, especially for the swing phase of gait.

Test-retest reliability and concurrent validity assessment of a novel high-frequency sensor device for anterior tibial translation measurement in loaded and unloaded condition: an exploratory cross-sectional study.

BACKGROUND: Magnetic resonance imaging (MRI) and manual tests remain the standard for diagnosing anterior cruciate ligament (ACL) rupture. Furthermore, the passive knee displacement, also described as anterior tibial translation (ATT), is used in order to make decisions about surgery or to assess rehabilitation outcomes. Unfortunately, these manual tests are limited to passive situations, and their application to assess knee stability in loaded, weight-bearing positions are missing. Therefore, a new device with high-performance sensors and a new sensor setting was developed. The aim of this exploratory cross-sectional study was to assess the test-retest reliability of this new device in a first step and the concurrent validity in a second step. METHODS: A total of 20 healthy volunteers were measured. Measurement consistency of the new device was assessed on the basis of reliability during Lachman test setting and in loaded position by artificial knee perturbation in a test-retest procedure. In a second step, the concurrent validity was evaluated with the Lachmeter® as a reference instrument. Intraclass correlation coefficient (ICC), standard error of measurement (SEM), the minimal detectable change (MDC) and Bland-Altman analysis were evaluated to assess the quality criteria. RESULTS: The measurements with the new device during the Lachman test provided a mean ATT of 5.46±2.22mm. The SEM ranged from 0.60 to 0.69mm resulting in an MDC between 1.67 and 1.93mm for the new device. In the loaded test situation, the mean ATT was 2.11±1.20mm, with test-retest reliability also showing good correlation (r>0.83). The comparison of the two measurement methods with an ICC of (r>0.89) showed good correlation, which also underlines the reasonable agreement of the Bland-Altman analysis. CONCLUSIONS: The evaluation of the test-retest reliability of the new device during the knee stability testing in passive situation as well as in a functional, loaded situation presented good reliability. In addition, the new device demonstrated good agreement with the reference device and therefore good validity. Furthermore, the quality criteria demonstrated the ability of the new device to detect the cut-off value (3-5mm) described in the literature for the diagnosis of ACL-deficient knees, which underlines the clinical relevance of this new device as a reliable and valid tool.

Mobile medial pivot (lateral slide)-type total knee arthroplasty exhibited different motion patterns between under anaesthesia and weight-bearing condition.

PURPOSE: Total knee arthroplasty (TKA), which has medial pivot and mobile-bearing mechanisms, has been developed and clinically used. However, the in vivo dynamic kinematics of the mobile medial pivot-type TKA (MMPTKA) is unclear. This study analysed the in vivo kinematics of MMPTKA in weight-bearing and nonweight-bearing conditions. METHODS: The study included 10 knees that underwent primary TKA using MMPTKA. After TKA, lateral view radiographs of the knee in full extension, 90° of flexion and passive full flexion were taken under general anaesthesia in the nonweight-bearing condition. At least 6 months postoperatively, knee motion during squatting from a weight-bearing standing position was observed using a flat-panel detector and analysed using the three-dimensional-to-two-dimensional image registration technique. RESULTS: Under anaesthesia: in passive full flexion, the anteroposterior (AP) locations of the femoral component's medial and lateral distal points were 10.2 and 16.0 mm posterior, and the rotational angles of the femoral component's X-axis (FCX) and insert were 8.1° external rotation and 18.5° internal rotation to full extension, respectively. Squatting: the AP translations of the femoral component's medial and lateral most distal points were 2.2 and 6.4 mm, and the rotational angles of the FCX and insert were 5.7° and 1.6° external rotation, respectively. Significant differences were observed in the AP translation of the femoral component's medial and lateral most distal points and changes in the insert's rotational angle when comparing under anaesthesia and squatting. CONCLUSIONS: The kinematics of the insert in MMPTKA was significantly influenced by loading and muscle contraction. The femoral component exhibited substantial external rotation and posterior translation under anaesthesia, which may contribute to achieving an optimal range of motion. The insert remained relatively stable during squatting and minimal rotation was observed, indicating good stability. MMPTKA was expected to demonstrate rational kinematics by incorporating mobile and medial pivot mechanisms. LEVEL OF EVIDENCE: Level IV, prospective biomechanical case series study.

Knee kinematics are not different between asymmetrical and symmetrical tibial baseplates in total knee arthroplasty: A fluoroscopic analysis of step-up and lunge motions.

PURPOSE: This clinical fluoroscopy study investigated knee kinematics of two different cemented fixed-bearing, posterior-stabilised (PS) total knee arthroplasty (TKA) designs: an asymmetric tibial component including an asymmetric insert designed to optimise personalised balance and fit and its precursor symmetrical design with symmetric insert. METHODS: A consecutive series of patients (16 TKAs from each treatment group) participating in a randomised controlled trial comparing TKA migration was included. The exclusion criterion was the use of walking aids. Flat-panel fluoroscopic recordings of step-up and lunge motions were acquired 1-year postoperatively. Medial and lateral contact points (CPs) were determined to calculate CP displacement, femoral axial rotation and pivot position. Using linear mixed-effects modelling techniques, kinematics between TKA designs were compared. RESULTS: During knee extension between 20° flexion and full extension, the CPs moved anteriorly combined with a small internal femoral rotation (a screw-home mechanism). Whereas CP movement was reversed: femoral rollback, external femoral rotation while flexing the knee between full extension and 20° knee flexion, At larger flexion angles, femoral axial rotation (FAR) occurred around a lateral pivot point both during step-up and lunge. The symmetric design had a 2.3° larger range of FAR compared to the asymmetric design during lunge (p = 0.02). All other kinematics were comparable. CONCLUSION: Despite the differences in design, this study showed that the asymmetric and symmetric PS TKA designs had mostly comparable knee kinematics during step-up and lunge motions. It is therefore expected that the functionality of the successor TKA design is similar to that of its precursor design. LEVEL OF EVIDENCE: Level II, prospective comparative study.

Gait kinematics and knee stability 10-years following posterior-stabilised total knee arthroplasty comparable to healthy adults >55.

PURPOSE: The purpose of this study was to compare the long-term objective biomechanical and functional parameters of a high-flexion total knee arthroplasty (TKA) design against healthy older adults to determine whether knee biomechanics are comparable in both populations. METHODS: One cohort of patients with a primary TKA, and a cohort of healthy adults over 55 years old with no musculoskeletal deficits or arthritis participated. Bilateral knee range of motion (RoM) was assessed with a goniometer, and gait patterns were analysed with a three-dimensional-motion capture system. An arthrometer quantified the anterior-posterior laxity of each knee. Statistical analyses were performed in SPSS software (α = 0.05). RESULTS: Twenty-three knees were replaced in 20 patients. At 9.8 ± 3.1 years postoperatively, patients' knees had a statistically significantly poorer RoM than healthy controls' knees (n = 23) due to limited flexion; p < 0.0001. Patients also failed to achieve the same degree of knee flexion as controls during downhill gait. No kinematic differences were observed during mid-flexion in level nor downhill gait; a state that has been associated with instability (p = 0.614; not significant [n.s]). There were no differences between groups in knee laxity (n.s). CONCLUSION: Patients in this study had similar gait patterns to healthy older adults during mid-flexion and were no more likely than the healthy controls to exhibit anterior-posterior translation of the knee > 7 mm; a known risk factor of instability. However, the knee flexion range was poorer. This likely led to bilateral pathological knee flexion patterns during downhill gait. LEVEL OF EVIDENCE: Level III.

Referencing the center of the femoral head during robotic or computer-navigated primary total knee arthroplasty results in less femoral component flexion than the traditional intramedullary axis.

BACKGROUND: During robotic and computer-navigated primary total knee arthroplasty (TKA), the center of the femoral head is utilized as the proximal reference point for femoral component position rather than the intramedullary axis. We sought to analyze the effect on femoral component flexion-extension position between these two reference points. METHODS: We obtained CT 3D-reconstructions of 50 cadaveric intact femurs. We defined the navigation axis as the line from center of the femoral head to center of the knee (lowest point of the trochlear groove) and the intramedullary axis as the line from center of the knee to center of the canal at the isthmus. Differences between these axes in the sagittal plane were measured. Degree of femoral bow and femoral neck anteversion were correlated with the differences between the two femoral axes. RESULTS: On average, the navigated axis was 1.4° (range, -1.4° to 4.1°) posterior to the intramedullary axis. As such, the femoral component would have on average 1.4° less flexion compared with techniques referencing the intramedullary canal. A more anterior intramedullary compared with navigated axis (i.e., less femoral flexion) was associated with more femoral bow (R2 = 0.7, P < 0.001) and less femoral neck anteversion (R2 = 0.5, P < 0.05). CONCLUSION: Computer-navigated or robotic TKA in which the center of the femoral head is utilized as a reference point, results in 1.4° less femoral component flexion than would be achieved by referencing the intramedullary canal. Surgeons should be aware of these differences as they may ultimately influence knee kinematics.

Isolated meniscus allograft transplantation with soft-tissue technique effectively reduces knee laxity in the presence of previous meniscectomy: In-vivo navigation of 18 consecutive cases.

OBJECTIVES: Although meniscal allograft transplantation (MAT) is a well-established procedure with satisfactory clinical results, limited in vivo kinematic information exists on the effect of medial and lateral MAT performed in the clinical setting. The purpose of the present study was to evaluate the biomechanical effect of arthroscopic isolated medial and lateral MAT with a soft-tissue fixation on pre- and post-operative knee laxity using a surgical navigation system. METHODS: 18 consecutive patients undergoing MAT (8 medial, 10 lateral) were enrolled. A surgical navigation system was used to quantify the anterior-posterior displacement at 30 and 90 degrees of knee flexion (AP30 and AP90), the varus-valgus rotation at 0 and 30 degrees of knee flexion (VV0 and VV30) and the dynamic laxity on the pivot-shift test (PS), which was determined through the anterior displacement of the lateral tibial compartment (APlat) and posterior acceleration of the lateral tibial compartment during tibial reduction (ACC). Data from laxity before and after MAT were compared through paired t-test (p â€‹< â€‹0.05). RESULTS: After medial MAT, there was a significant decrease in tibial translation of 3.1 â€‹mm (31%; p â€‹= â€‹0.001) for AP30 and 2.3 â€‹mm (27%; p â€‹= â€‹0.020) for AP90, a significant difference of 2.5° (50%; p â€‹= â€‹0.002) for VV0 and 1.7° (27%; p â€‹= â€‹0.012) for VV30. However, medial MAT did not determine any reduction in the PS kinematic data. Lateral MAT determined a significant decrease in the tibial translation of 2.5 â€‹mm (38%; p â€‹< â€‹0.001) for AP30 and 1.9 â€‹mm (34%; p â€‹= â€‹0.004) for AP90 as well as a significant difference of 3.4° (59%; p â€‹< â€‹0.001) for VV0 and of 1.7° (23%; p â€‹= â€‹0.011) for VV30. There was also a significant reduction of the PS of 4.4 â€‹mm (22%; p â€‹= â€‹0.028) for APlat and 384.8 â€‹mm/s2 (51%; p â€‹= â€‹0.005) for ACC. CONCLUSION: MAT with soft-tissue fixation results in a significant laxity reduction in an in-vivo setting. Medial MAT improved knee kinematics by determining a significant reduction with particular emphasis on AP translation and VV manoeuvre. Conversely, Lateral MAT determined a massive reduction of the PS and a mild decrease of the AP translation and VV manoeuvre. STUDY DESIGN: Controlled laboratory study.

Dynamic CT scanning of the knee: Combining weight bearing with real-time motion acquisition.

BACKGROUND: Imaging the lower limb during weight-bearing conditions is essential to acquire advanced functional joint information. The horizontal bed position of CT systems however hinders this process. The purpose of this study was to validate and test a device to simulate realistic knee weight-bearing motion in a horizontal position during dynamic CT acquisition and process the acquired images. METHODS: "Orthostatic squats" was compared to "Horizontal squats" on a device with loads between 35% and 55% of the body weight (%BW) in 20 healthy volunteers. Intraclass Correlation Coefficient (ICC), and standard error of measurement (SEM), were computed as measures of the reliability of curve kinematic and surface EMG (sEMG) data. Afterwards, the device was tested during dynamic CT acquisitions on three healthy volunteers and three patients with patellofemoral pain syndrome. The respective images were processed to extract Tibial-Tuberosity Trochlear-Groove distance, Bisect Offset and Lateral Patellar Tilt metrics. RESULTS: For sEMG, the highest average ICCs (SEM) of 0.80 (6.9), was found for the load corresponding to 42%BW. Kinematic analysis showed ICCs were the highest for loads of 42%BW during the eccentric phase (0.79-0.87) and from maximum flexion back to 20° (0.76). The device proved to be safe and reliable during the acquisition of dynamic CT images and the three metrics were computed, showing preliminary differences between healthy and pathological participants. CONCLUSIONS: This device could simulate orthostatic squats in a horizontal position with good reliability. It also successfully provided dynamic CT scan images and kinematic parameters of healthy and pathological knees during weight-bearing movement.

Design, Kinematics and Gait Analysis, of Prosthetic Knee Joints: A Systematic Review.

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.

Integration of statistical shape modeling and alternating interpolation-based model tracking technique for measuring knee kinematics in vivo using clinical interleaved bi-plane fluoroscopy.

Background: A 2D fluoroscopy/3D model-based registration with statistical shape modeling (SSM)-reconstructed subject-specific bone models will help reduce radiation exposure for 3D kinematic measurements of the knee using clinical alternating bi-plane fluoroscopy systems. The current study aimed to develop such an approach and evaluate in vivo its accuracy and identify the effects of the accuracy of SSM models on the kinematic measurements. Methods: An alternating interpolation-based model tracking (AIMT) approach with SSM-reconstructed subject-specific bone models was used for measuring 3D knee kinematics from dynamic alternating bi-plane fluoroscopy images. A two-phase optimization scheme was used to reconstruct subject-specific knee models from a CT-based SSM database of 60 knees using one, two, or three pairs of fluoroscopy images. Using the CT-reconstructed model as a benchmark, the performance of the AIMT with SSM-reconstructed models in measuring bone and joint kinematics during dynamic activity was evaluated in terms of mean target registration errors (mmTRE) for registered bone poses and the mean absolute differences (MAD) for each motion component of the joint poses. Results: The mmTRE of the femur and tibia for one image pair were significantly greater than those for two and three image pairs without significant differences between two and three image pairs. The MAD was 1.16 to 1.22° for rotations and 1.18 to 1.22 mm for translations using one image pair. The corresponding values for two and three image pairs were 0.75 to 0.89° and 0.75 to 0.79 mm; and 0.57 to 0.79° and 0.6 to 0.69 mm, respectively. The MAD values for one image pair were significantly greater than those for two and three image pairs without significant differences between two and three image pairs. Conclusions: An AIMT approach with SSM-reconstructed models was developed, enabling the registration of interleaved fluoroscopy images and SSM-reconstructed models from more than one asynchronous fluoroscopy image pair. This new approach had sub-millimeter and sub-degree measurement accuracy when using more than one image pair, comparable to the accuracy of CT-based methods. This approach will be helpful for future kinematic measurements of the knee with reduced radiation exposure using 3D fluoroscopy with clinically alternating bi-plane fluoroscopy systems.

Comparison of accuracy for hip-knee-ankle (HKA) angle by X-ray and knee motion analysis system and the relationships between HKA and gait posture.

BACKGROUND: The lower limb mechanical axis was used to assess the severity of knee osteoarthritis (KOA) with varus/valgus deformity and the accuracy of targeted lower limb alignment correction after operation by conventional X-rays. There are lots of parameters to assess the gait in elder patients such as velocity, stride length, step width and swing/stance ratio by knee joint movement analysis system. However, the correlation between the lower limb mechanical axis and gait parameters is not clear. This study is aimed at obtaining the accuracy of the lower limb mechanical axis by the knee joint movement analysis system and the correlation between the lower limb mechanical axis and gait parameters. METHODS: We analysed 3D knee kinematics during ground gait of 99 patients with KOA and 80 patients 6 months after the operations with the vivo infrared navigation 3D portable knee joint movement analysis system (Opti-Knee®, Innomotion Inc, Shanghai, China). The HKA (Hip-Knee-Ankle) value was calculated and compared to X-ray findings. RESULTS: HKA absolute variation after the operation was 0.83 ± 3.76°, which is lower than that before the operation (5.41 ± 6.20°, p = 0.001) and also lower than the entire cohort (3.36 ± 5.72). Throughout the cohort, a significant correlation with low coefficients (r = -0.19, p = 0.01) between HKA value and anterior-posterior displacement was found. In comparing the HKA values measured on the full-length alignment radiographs and 3D knee joint movement analysis system (Opti-Knee), there was a significant correlation with moderate to high coefficients (r = 0.784 to 0.976). The linear correlation analysis showed that there was a significant correlation between the values of HKA measured by X-ray and movement analysis system (R2 = 0.90, p < 0.01). CONCLUSIONS: Data with equivalent results as HKA, the 6DOF of the knee and ground gait data could be provided by infrared navigation based 3D portable knee joint movement analysis system comparing with the conventional X-rays. There is no significant effect of HKA on the kinematics of the partial knee joint.

Progression of varus deformity in osteoarthritic knees induces anterior paradoxical motion of the femur during early knee flexion.

PURPOSE: The purpose of this study was to investigate the position of the femur relative to the tibia throughout range of motion in the osteoarthritic knee to evaluate knee kinematics and assess its relationship with the degree of varus deformity. METHODS: In this study, 116 preoperative knees with varus deformity were evaluated using a navigation system. The internal-external, anteroposterior, and mediolateral positions of the femur relative to the tibia were measured at maximum extension, 15°, 30°, 45°, 60°, 90°, 105°, and 120°, and maximum flexion angles. From these parameters, two-dimensional translation of the surgical epicondylar axis was projected onto the tibial axial plane, and the femoral movement was evaluated relative to the tibia. In addition, the knees were retrospectively classified into three groups according to their degrees of preoperative hip-knee-ankle angle: mild (< 10°), moderate (10°-20°), and severe (> 20°). Then, the differences in each parameter between these groups were investigated. The Steel-Dwass test was performed to identify the difference among three groups. Statistical significance was set at p values < 0.05. RESULTS: There was a significant difference in the anteroposterior position of the femur relative to the tibia among the three groups, especially from extension to early flexion (p < 0.05). The anteroposterior position at knee extension deviated posteriorly according to the progression of varus deformity. Rotational and mediolateral translation were not significantly different among the groups. Normal knee kinematics were diminished in almost all cases in each group. In addition, anterior paradoxical motion of the femur during early knee flexion was observed in 45.6% (n = 26), 57.1% (n = 28), and 80.0% (n = 8) of cases in the mild, moderate, and severe groups, respectively. The anteroposterior position of the femur relative to the tibia at knee extension was significantly more posterior in patients with than in those without anterior paradoxical motion (p < 0.0001). CONCLUSION: The anteroposterior position of the femur relative to the tibia changed according to the progression of varus deformity in osteoarthritic knees, especially from knee extension to early flexion. Posterior deviation of the femur at knee extension induced its anteroposterior movement relative to the tibia, resulting in anterior paradoxical motion. LEVEL OF EVIDENCE: III.

Patellar tendon elastic properties derived from in vivo loading and kinematics.

Patellar complications frequently limit the success of total knee arthroplasty. In addition to the musculoskeletal forces themselves, patellar tendon elastic properties are essential for driving patellar loading. Elastic properties reported in the literature exhibit high variability and appear to differ according to the methodologies used. Specifically in total knee arthroplasty patients, only limited knowledge exists on in vivo elastic properties and their corresponding loads. For the first time, we report stiffness, Young's modulus, and forces of the patellar tendon, derived from four patients with telemetric total knee arthroplasties using a combined imaging and measurement approach. To achieve this, synchronous in vivo telemetric assessment of tibio-femoral contact forces and fluoroscopic assessment of knee kinematics, along with full body motion capture and ground reaction forces, fed musculoskeletal multi-body models to quantify patellar tendon loading and elongation. Mechanical patellar tendon properties were calculated during a squat and a sit-stand-sit activity, with resulting tendon stiffness and Young's modulus ranging from 511 to 1166 N/mm and 259 to 504 MPa, respectively. During these activities, the patellar tendon force reached peak values between 1.31 and 2.79 bodyweight, reaching levels of just âˆ¼0.5 bodyweight below the tibio-femoral forces. The results of this study provide valuable input data for mechanical simulations of the patellar tendon and the whole resurfaced knee.

Validity and Reliability of a Wearable Goniometer Sensor Controlled by a Mobile Application for Measuring Knee Flexion/Extension Angle during the Gait Cycle.

Knee kinematics during gait is an important assessment tool in health-promotion and clinical fields. This study aimed to determine the validity and reliability of a wearable goniometer sensor for measuring knee flexion angles throughout the gait cycle. Twenty-two and seventeen participants were enrolled in the validation and reliability study, respectively. The knee flexion angle during gait was assessed using a wearable goniometer sensor and a standard optical motion analysis system. The coefficient of multiple correlation (CMC) between the two measurement systems was 0.992 ± 0.008. Absolute error (AE) was 3.3 ± 1.5° (range: 1.3-6.2°) for the entire gait cycle. An acceptable AE (<5°) was observed during 0-65% and 87-100% of the gait cycle. Discrete analysis revealed a significant correlation between the two systems (R = 0.608-0.904, p ≤ 0.001). The CMC between the two measurement days with a 1-week interval was 0.988 ± 0.024, and the AE was 2.5 ± 1.2° (range: 1.1-4.5°). A good-to-acceptable AE (<5°) was observed throughout the gait cycle. These results indicate that the wearable goniometer sensor is useful for assessing knee flexion angle during the stance phase of the gait cycle.

Effects of soft tissue artifacts on the calculated kinematics of the knee during walking and running.

Kinematics of the knee during gait has mostly been studied using optical motion capture systems (MCS). The presence of soft tissue artifacts (STA) between the skin markers and the underlying bone presents a major impediment to obtaining a reliable joint kinematics assessment. In this study, we determined the effects of STA on the calculation of knee joint kinematics during walking and running, through the combination of high-speed dual fluoroscopic imaging system (DFIS) and magnetic resonance imaging technique. Ten adults walked and ran while data was collected simultaneously from MCS and high-speed DFIS. The study showed that measured STA underestimated knee flexion angle, but overestimated knee external and varus rotation. The absolute error values of the skin markers derived from knee flexion-extension angle, internal-external rotation, and varus-valgus rotation during walking were -3.2 ± 4.3 deg, 4.6 ± 3.1 deg, and 4.5 ± 3.2 deg respectively, and during running were -5.8 ± 5.4 deg, 6.6 ± 3.7 deg, and 4.8 ± 2.5 deg respectively. Average errors relative to the DFIS for flexion-extension angle, internal-external rotation, and varus-valgus rotation were 78 %, 271 %, 265 % during walking respectively, and were 43 %, 106 %, 200 % during running respectively. This study offers reference for the kinematic differences between MCS and high-speed DFIS, and will contribute to optimizing methods for analyzing knee kinematics during walking and running.

Impact of Pilates mat-based exercises on knee kinematics during running.

INTRODUCTION: Core strengthening, balance, and flexibility programs such as Pilates have been advocated to positively impact running mechanics and prevent lower extremity injuries. The purpose of this study was to assess the effects of a 12-week mat-based Pilates exercise program on dynamic knee valgus alignment in runners. METHODS: Thirty-four novice runners, including young male and female adults performed a running protocol at baseline. The protocol consisted of the participants running on a treadmill at a constant five miles per hour (mph) for 4 min. Post-examination, participants were randomly assigned to a Pilates or control group (n = 16 and n = 18, respectively). A certified Pilates instructor gave the Pilates group a 12-week home-based program. To ensure participants in the Pilates group performed exercises correctly, the Pilates instructor conducted the first session, and provided feedback to each participant. Participants in both groups performed the same running testing protocol every four weeks. Knee valgus was measured as the medial displacement of the knee joint center during the running stance phase. Repeated measures Analysis of Variance (RepANOVA) was calculated at baseline and 4-, 8-, and 12-weeks post examinations to compare knee valgus during running. RESULTS: Although a reduction in dynamic knee valgus was observed within the Pilates group, the RepANOVA analysis revealed this change was not statistically significant. CONCLUSIONS: Pilates mat-based exercises may improve knee valgus after 12 weeks but a larger sample size, longer intervention duration, or a supervised program should be considered for future research to evaluate its effectiveness.