Search Results (2,745)

Knee osteoarthritis (KOA) is a leading cause of pain and disability worldwide, and current treatments remain largely symptomatic, with no disease-modifying therapy established for routine use. This narrative review evaluates extracellular vesicles (EVs) as biological nanocarriers and a cell-free alternative to mesenchymal stromal cell therapy for KOA by examining the biological rationale, preclinical evidence, clinical studies, and current methodological and regulatory requirements. Preclinical findings indicate that EVs may exert immunomodulatory, anti-inflammatory, and chondroprotective effects, supporting their potential to influence joint homeostasis. The review also summarizes current recommendations for EV nomenclature, characterization, and quality control in accordance with the Minimal Information for Studies of EVs 2023 guidelines and highlights key translational challenges, including scalable manufacturing, potency assessment, and regulatory compliance. Clinical evidence to date suggests a favorable safety profile, but efficacy data remain limited and inconsistent; a randomized placebo-controlled trial showed no superiority over placebo, whereas small early human studies suggested possible benefit in selected cases. Overall, EVs represent a promising cell-free strategy for KOA, but current evidence is insufficient to support routine clinical use, emphasizing the need for standardized production, validated potency assays, and robust randomized clinical trials. Full article

The squat is a fundamental multi-joint movement widely studied in strength training and biomechanics. While numerous experimental and computational studies have examined squat kinematics and joint loading, the mechanisms governing how squat technique adapts to increasing external load remain insufficiently understood. In particular, inverse-dynamics-based approaches often overlook explicit constraints imposed by limited joint moment capacity. This study presents a computational framework for predicting load-dependent adaptations of squat posture. The human body was represented as a multi-segment rigid-body system, with joints modeled as nonlinear rotational elements with bounded moment capacity. A reference squat trajectory was first generated kinematically, and a constrained optimization procedure was then applied at each motion frame to determine a mechanically admissible posture under increasing barbell load. The results show that higher loads lead to systematic posture adaptations, including increased torso inclination and redistribution of rotational demand from the knee toward the hip joint. For the highest load, peak torso pitch increased from 30° to over 40°, while joint utilization exceeded unity, indicating the onset of yielding. These findings identify joint moment capacity as a key constraint governing squat technique and demonstrate the potential of the proposed framework for predictive biomechanical analysis. Full article

Anterior cruciate ligament (ACL) injury risk is elevated in female youth football, yet knee joint loading has mainly been studied under controlled laboratory conditions. This limits understanding of how injury risk emerges during realistic match situations. This study provided a field-based kinetic characterization of football-specific movements by estimating knee abduction moments (KAMs) using wearable sensors and machine learning. Fifty-two highly talented female youth players performed agility tasks during training, including structured exercises (F-EX) and game-based play (F-GAME). Full-body kinematics were collected with inertial measurement units, and a validated support vector machine model, trained on synchronized motion capture and force plate data, classified trials as high or low KAM. Across 662 change-in-direction trials, 9–12% were classified as high KAM in both conditions, indicating that potentially high-risk loading regularly occurs during routine actions. High KAM trials showed reduced knee and pelvis flexion, increased hip flexion, and greater pelvis rotation toward the cutting direction, reflecting upright, stiff movement strategies. Performance analyses revealed smaller cut angles in exercises and greater approach acceleration in game play, without differences in peak velocity. These findings demonstrate the feasibility of field-based kinetic screening and support a complex-systems perspective on ACL injury risk. Full article

The purpose of this study was to examine associations between lower-limb mechanical strength, phase-oriented composite strength indices, generalized neuromuscular activation, and maximal soccer ball kicking speed in trained athletes. Twenty-five male soccer players (age: 20.64 ± 2.50 years; height: 179.28 ± 4.27 cm; body mass: 75.80 ± 9.41 kg) participated in this cross-sectional study. Isometric ankle and knee joint torques were assessed using an isokinetic dynamometer, and joint-specific and phase-oriented cross-joint composite indices were computed to represent integrated strength capacity across the kinetic chain. Neuromuscular activation was evaluated via surface electromyography during a standardized squat jump task. Ball-kicking speed was measured using Doppler radar during maximal instep kicks. Associations were analyzed using Pearson correlation coefficients (p ≤ 0.05) with false discovery rate correction for multiple comparisons. In unadjusted analyses, moderate positive correlations were observed for several ankle torque variables and composite ankle strength indices, while swing-phase composite measures demonstrated moderate correlations (r = 0.43–0.55). Knee strength indices and sEMG variables showed no significant relationships. However, none of the variables remained statistically significant after FDR correction, suggesting limited independent explanatory value of isolated isometric strength and non-task-specific neuromuscular activation assessed during a standardized squat jump for maximal kicking performance. Full article

Knee joint moment is an important biomechanical parameter for sports assessment, rehabilitation monitoring, and human–machine interaction. However, direct measurement is often restricted to laboratory-based settings. Surface electromyography (sEMG) offers a non-invasive alternative for indirect joint moment estimation, but many existing deep learning models remain too computationally demanding for potential wearable edge deployment. To address this gap, this study proposes Topo2DCNN-LSTM, a lightweight two-dimensional (2D) convolutional neural network model, designed for sagittal-plane knee flexion moment estimation. The model used a feature-based sequential representation, transforming raw sEMG signals into compact Root Mean Square (RMS) feature frames. The input was processed by a lightweight 2D convolutional neural network (CNN) encoder and paired with long short-term memory (LSTM) units. The model was trained on a public walking dataset of healthy subjects with synchronized sEMG and joint kinetics at two treadmill speeds. When compared with selected deep learning baselines, the quantized model achieved a mean RMS Error of 0.088 ± 0.020 Nm/kg at 1.2 m/s and 0.114 ± 0.034 Nm/kg at 1.8 m/s. On a SparkFun Thing Plus–SAMD51, it achieved an average inference latency of 28 ms using 71,316 bytes of random-access memory (RAM) and 257,172 bytes of flash. These results support its use as a proof of concept for personalized unilateral knee moment estimation with isolated on-device inference feasibility under resource-constrained and limited walking conditions. Full article

The badminton smash is a decisive scoring technique whose effectiveness depends on adequate preparation and a proper proximal-to-distal sequencing of the kinetic chain. This study integrates a You Only Look Once (YOLO)-based real-time vision detector with five wearable inertial measurement units (IMUs) attached to the right shoulder, right elbow, right wrist, right hip, and right knee of right-handed players. A high-speed camera provides video for shuttlecock and joint localization via YOLO, and the IMUs provide instantaneous joint accelerations at impact. The following four coaching-oriented indicators are defined: (1) rapid lowering of the center of mass after the opponent’s shot; (2) immediate forward acceleration after the shuttle is released; (3) alignment at the hitting position with the right shoulder/hip rotated backward and the left shoulder facing the approaching shuttle; and (4) a proximal-to-distal sequence in which the shoulder leads the elbow and then the wrist. Using two athletes with 15 trials each, the system achieved an overall recognition accuracy above 93% against manually annotated video. The method can provide objective feedback for coaches and players and is suitable for instructional use in physical education classes. Full article

Background/Objectives: Multiple epiphyseal dysplasia (MED) is a clinically and genetically heterogeneous group of disorders characterized by a waddling gait, joint pain, and early-onset osteoarthritis. The aim of this study was to compare the genetic characteristics and long-term clinical follow-up findings of 22 patients with MED from 17 unrelated families. Methods: Molecular diagnosis was performed using clinical exome analysis and exome sequencing. Seventeen children were followed for a median of 5.5 years. Results: Eighteen disease-related variants were identified: 47% in COMP, 11.8% each in COL9A2 and COL9A3 in a monoallelic state, 17.6% in SLC26A2, and 11.8% each in MATN3 and CANT1 in a biallelic state. Some COMP mutations previously identified in pseudoachondroplasia, an allelic disorder of MED1, were shown in our study to exhibit a typical MED1 or intermediate phenotype. In contrast, it was confirmed that certain mutations in SLC26A2 lead to MED4 phenotype. Furthermore, it has been observed that biallelic variants in MATN3 may be associated with the MED5 phenotype. In patients with MED2 and MED3, the knee joint is affected, while in other types, the hip joint is predominantly affected. In 15 children followed until ages 11–18, height decreased slightly as they grew older but remained normal or at the lower limit, and slow progression was observed in the waddling gait and joint pain, except in the intermediate form. Conclusions: This study reveals the frequency of disease-related variants, including seven novel ones, in genes leading to MED1–5 and 7 phenotypes, and expands the spectrum of genetic and clinical phenotypes. Full article

Introduction: Periprosthetic joint infections (PJI) are among the most serious and costly complications in orthopedic surgery, significantly affecting patient prognosis and healthcare systems. Despite rigorous aseptic measures, intraoperative contamination of sterile fields, instruments, and air remains a persistent source of potential infection. This study investigates the relationship between the microbial contamination of sterile fields during arthroplasty and postoperative inflammatory markers, with the objective of determining whether the contamination of sterile fields correlates with the presence of periprosthetic joint infection (PJI). Material and Methods: This prospective observational study included 33 patients undergoing total hip or knee arthroplasty in a university-affiliated orthopedic center. Intraoperative samples were collected from sterile fields and equipment to detect microbial contamination, while postoperative monitoring involved the C-reactive protein (CRP); erythrocyte sedimentation rate (ESR); leukocyte count; temperature; and wound assessment on days 1, 3 and 7. All patients received 48 h of prophylactic cefuroxime. Statistical analysis was conducted using the International Business Machines (IBM) Statistical Product and Service Solutions (SPSS) software for Windows, version 30.0 (IBM Corporation, Armonk, New York, United States of America) with significance set at p ≤ 0.05. Results: Postoperative inflammatory markers showed distinct patterns depending on the isolated microorganism, with Proteus vulgaris and Staphylococcus hominis ssp. consistently associated with higher CRP and leukocyte values, indicating a more intense systemic response. Staphylococcus epidermidis was the most frequently isolated species but showed moderate inflammatory profiles, suggesting its potential role in subclinical colonization. A strong correlation between CRP on day 3 and leukocyte count (r = 0.81) confirms their combined utility in the early detection of infectious complications, while ESR appeared less dynamic and more complementary in nature. Discussion: This study highlights the significant role of intraoperative contamination and microbial virulence in shaping the postoperative inflammatory response after arthroplasty. Elevated CRP and leukocyte levels, particularly on day 3, were closely associated with pathogens known for biofilm formation and chronic infections. Despite prophylactic antibiotic use, confirmed infections still occurred, suggesting the need to reassess current protocols and enhance intraoperative contamination control. Conclusions: Pathogen presence in sterile fields during arthroplasty increases the risk of periprosthetic joint infections, often without early clinical symptoms. CRP on day 3 and leukocyte count were the most reliable early indicators of persistent inflammation. Full article

The purpose of this study was to compare knee joint biomechanical characteristics and movement strategies according to the direction of the forward lunge in badminton and to provide practical insights for training and injury prevention. Eighteen female recreational badminton players performed forward lunges in three directions: center (CFL), left (LFL), and right (RFL). Knee joint angles and moments, center of mass (COM) velocity, ground reaction forces (GRF), and knee extensor and flexor muscle forces were analyzed. In addition, continuous biomechanical variables were examined using statistical non-parametric mapping (SnPM). The results showed that LFL demonstrated the fastest approach COM velocity and greater knee flexion moments at initial contact, along with the greatest knee flexor muscle force, which may be indicative of enhanced joint stabilization demand. RFL exhibited a smaller knee flexion angle and lower vertical ground reaction force but showed the greatest posterior braking force and the fastest recovery COM velocity, which may be indicative of greater movement efficiency. CFL showed significantly greater knee adduction angles and internal rotation moments, suggesting elevated rotational loading at the knee that may be associated with increased injury risk. These findings highlight direction-specific knee joint biomechanical characteristics during badminton forward lunges and may provide useful information for developing targeted training and injury prevention approaches. Full article

Background/Objectives: Knee joint instability is frequently reported in individuals with knee osteoarthritis (OA) and may persist after total knee replacement (TKR), where it represents a leading cause of revision. However, neuromuscular factors associated with knee instability remain poorly understood. This systematic review and meta-analysis aimed to compare neuromuscular characteristics between individuals with stable and unstable knees in OA and TKR populations. Methods: PubMed, CENTRAL, Scopus, and EMBASE were searched from inception to 10 January 2025. Studies comparing neuromuscular outcomes between stable and unstable knees were included. Neuromuscular parameters included: muscle strength, muscle power, muscle activation pattern, and joint stiffness. Where appropriate, pooled standardized mean differences (SMD) were calculated using random-effects models. Certainty of evidence was evaluated using the GRADE approach. Results: Nineteen studies (16 OA, 3 TKR; n = 7369 participants) were included, with eleven studies eligible for meta-analysis. OA individuals with unstable knees demonstrated significantly lower limb muscle strength compared with stable counterparts (SMD = −0.49, 95% CI −0.81 to −0.16, p = 0.003). Muscle co-contraction did not differ significantly between groups (SMD = 0.12, 95% CI −0.70 to 0.94, p = 0.77). The overall certainty of evidence was rated as very low. Conclusions: Knee instability in OA populations is associated with reduced lower limb muscle strength, although evidence quality is limited and findings regarding neuromuscular control strategies remain inconclusive. Evidence in TKR populations is scarce. Future studies should investigate muscle activation patterns and dynamic joint stabilization during functional tasks to clarify the neuromuscular mechanisms underlying knee instability. Full article

Compliant mechanisms have contributed to many advances in soft robotics, and there is strong motivation to translate these ideas to assistive devices where adaptive motion at the human interface is required. This work presents novel reconfigurable compliant joints (RCJs) as a parameterized joint element for functional biomimicry in lower-extremity joints for prosthetic knees and ankle–foot orthoses, with concepts that extend to other limb joints. The RCJ uses a rigid hub and outer ring joined by an array of flexible links with centerlines defined by cubic Bézier curves. Link shapes are organized into four Bézier classes (A–D), with base types using 10, 12, or 14 uniformly distributed link slots and variants generated by modifying active-link count and distribution, forming a structured morphology space of 12 configurations for machine design. Dual-extrusion 3D-printed prototypes are characterized by a custom testing apparatus using a 2.2 kN load cell at 25 mm/s over a 0–90° rotation range across six recorded load cycles to measure torque–angle curves and stiffness under large deformations. Angle-dependent stiffness is evaluated over three fixed intervals (0–30°, 30–60°, and 60–90°) to quantify multi-stage behavior. A 2-dimensional corotational frame model and a Simscape Multibody model, including a rolling-contact knee configuration, use the same parameterization to relate geometry, nonlinear mechanics, and system-level motion. Experiments and simulations show multi-stage torque–angle profiles and predictable stiffness modulation across all configurations, with both magnitude and transition angle tunable through Bézier class and active-link distribution, positioning the RCJ as a CAD/CAE-compatible joint architecture for assistive devices or wearable robotic systems and a basis for advancing functional biomimicry in compliant mechanism design. Full article

Background/Objectives: The medial meniscus is crucial for load transmission and knee stability. Meniscal tears disrupt joint biomechanics, increasing the risk of cartilage degeneration. However, few studies have quantitatively compared how different tear types affect stress and contact mechanics using finite element analysis (FEA). This study aims to analyze stress distributions for various meniscal tear types and develop a predictive model for meniscal stress behavior. This study investigates how stress distributions differ between healthy and torn medial menisci under identical loading conditions. The study examines which meniscal tear type produces the highest stress concentrations. The effects of different tear types on penetration, gap formation, pressure distribution, and sliding distance at the meniscus interface are also analysed. Materials and Methods: The FEA model of the knee joint, including femoral and tibial cartilage and the medial meniscus, was developed. Simulations were conducted for a healthy meniscus and for menisci with radial, horizontal and complex tears. Stress, penetration, gap, pressure, and sliding distance were calculated, and a mathematical model describing their relationships was established. Results: All torn menisci exhibited significantly higher stresses than the healthy meniscus (p < 0.001). Radial tears generated the highest stress concentrations (p < 0.001). Pressure was mainly influenced by meniscal geometry, while the gap remained nearly constant. Penetration increased slightly (p < 0.05). The predictive model demonstrated a strong correlation between meniscal stress and interface parameters (R² > 0.9). In a healthy meniscus, stress distribution is homogeneous (≈26 MPa). Stress concentration increases depending on the tear type: limited in a horizontal tear (≈26.5 MPa), significant in a vertical tear (≈30.8 MPa), and highest in a radial tear (≈40.6 MPa). These results indicate that as the tear progresses, the load-bearing capacity of the meniscus decreases, and stresses concentrate at the tear edges. Conclusions: Meniscal tears, especially radial ones, substantially alter knee biomechanics and elevate tissue stress. These biomechanical insights highlight the importance of early diagnosis and targeted rehabilitation strategies to prevent further cartilage damage and osteoarthritis progression. Full article

Patellar maltracking is among the most common causes of anterior knee pain after total knee arthroplasty (TKA), underscoring the need for accurate prevention and treatment. Therefore, the purpose of this narrative review is to provide a comprehensive overview of current evidence on post-TKA tracking, focusing on component alignment, preoperative patient assessment, and revision treatment options. A PubMed database search was performed, leveraging the literature from the last 20 years, and the results were qualitatively synthesized. According to current studies, several precautions should be taken to prevent patellofemoral stress and, consequently, patellar maltracking, such as avoiding internal rotation, valgus alignment, and excessive flexion of the femoral component and internal rotation of the tibial component. Regarding alignment strategies, kinematic alignment appears to offer potential benefits over mechanical alignment in certain functional outcomes and patient satisfaction scores. However, these differences should be interpreted cautiously as they may not always exceed the minimal clinically important difference. Furthermore, recent evidence indicates that quadriceps biomechanics influence TKA outcomes, potentially suggesting that conventional surgical approaches may need to be individualized, though these preliminary findings require prospective validation. Currently, robotic-assisted surgery represents a developmental direction for patient-tailored interventions and offers great promise for better prosthesis customization to the individual patient. Integration of imaging data with dynamic soft-tissue assessment enables more predictable reconstruction of joint kinematics. Regarding surgical treatment, the selection of specific methods requires a prior clinical and radiographic assessment. Indications range from patellar maltracking direction and component malrotation to patient preferences and rehabilitation potential. Ultimately, the future of TKA relies on personalized interventions to prevent complications and improve patient outcomes. This evolution is driven by the shift from mechanical alignment to kinematic alignment, alongside quadriceps tendon assessment and intraoperative robotic-assisted measurement, all aimed at optimizing the accuracy of implant positioning. Full article

Background: Late-onset anaerobic prosthetic joint infection (PJI) is uncommon but may indicate underlying, previously asymptomatic colorectal malignancy. While the association between Streptococcus bovis group (SBG) bacteremia and colorectal cancer is well established, links between anaerobic PJIs and colorectal neoplasia are rarely reported. Anaerobic organisms originating from the gastrointestinal tract may translocate via the hematogenous route, and their presence in PJI should prompt clinicians to consider occult colorectal pathology. Methods: All periprosthetic arthroplasty infection cases between 2015 and 2025 were reviewed. Clinical records, diagnostic findings, microbiological data, and treatment outcomes were analyzed. Results: Three female patients (mean age 76.3 years) presented with late-onset PJI occurring at least five years after primary total knee arthroplasty. Causative organisms included Bacteroides fragilis, Morganella morganii, and Klebsiella pneumoniae. All patients underwent two single-stage revision surgeries and one debridement, antibiotics and implant retention (DAIR) procedure. Cross-sectional computed tomography imaging of the abdomen and pelvis (CT-AP) performed to evaluate hematogenous sources of infection consistently revealed previously undiagnosed colorectal malignancy. One patient had additional metastatic disease. Postoperative complications included one case of pulmonary embolism; no other major complications were observed. Conclusions: Anaerobic PJIs are rare, and their association with colorectal malignancy is not well established. These cases highlight the importance of evaluating potential gastrointestinal sources, including occult colorectal cancer, in patients presenting with late-onset anaerobic PJI. Full article

Background and objectives: Articular cartilage provides low-friction articulation across joint surfaces, distributes loads, and absorbs stress, all of which are crucial mechanical functions of joints. Changes in the mechanical characteristics of cartilage are among the first signs of degenerative joint disease, and they are especially important for athletes who are subjected to high-impact, high-magnitude loading on a regular basis. The objective of this study was to: (i) compare the mechanical characteristics of tibiofemoral cartilage in healthy and osteoarthritic conditions across medial and lateral anatomical compartments; and (ii) use nonlinear phenomenological viscoelastic modeling in conjunction with unconfined compression testing to characterize compartment-specific viscoelastic behavior. Materials and Methods: Forty-six human tibiofemoral cartilage samples were collected during knee surgeries and classified as healthy (n = 17) or osteoarthritic (n = 29) and as medial (n = 26) or lateral (n = 20). Quasi-static unconfined compression tests were performed at 1 mm/min to obtain stress–strain responses, Young’s modulus, maximum compressive stress, and energy absorption. Viscoelastic behavior was analyzed using a nonlinear phenomenological viscoelastic model. Appropriate parametric or non-parametric statistical tests and effect size measures were applied. Results: Osteoarthritic cartilage’s stiffness and energy absorption were significantly higher than those of healthy tissue (p < 0.05). Medial cartilage exhibited significantly greater stiffness and stress than lateral cartilage (p < 0.001). The nonlinear phenomenological viscoelastic model provided an excellent fit (R² > 0.999). Conclusions: The mechanical profile of osteoarthritic tibiofemoral cartilage is characterized by pathological mechanical remodeling and increased stiffness. Greater mechanical susceptibility in the medial compartment supports the significance of cartilage biomechanical properties as sensitive indicators of early degeneration and osteoarthritis risk in athletic populations. Full article