BACKGROUND: Knee osteoarthritis (OA) is still challenging to prevent or treat. Enhanced endoplasmic reticulum (ER) stress and increased pyroptosis in chondrocytes may be responsible for cartilage degeneration. This study aims to investigate the effect of ER stress on chondrocyte pyroptosis and the upstream regulatory mechanisms, which have rarely been reported. METHODS: The expression of the histone methyltransferase enhancer of zeste homolog 2 (EZH2), microRNA-142-3p (miR-142-3p), and high mobility group box 1 (HMGB1) and the levels of ER stress, pyroptosis, and metabolic markers in normal and OA chondrocytes were investigated by western blotting, quantitative polymerase chain reaction, immunohistochemistry, fluorescence in situ hybridization, fluorescein amidite-tyrosine-valine-alanine-aspartic acid-fluoromethyl ketone (FAM-YVAD-FMK)/Hoechst 33342/propidium iodide (PI) staining, lactate dehydrogenase (LDH) release assays, and cell viability assessments. The effects of EZH2, miR-142-3p, and HMGB1 on ER stress and pyroptosis and the hierarchical regulatory relationship between them were analyzed by chromatin immunoprecipitation, luciferase reporters, gain/loss-of-function assays, and rescue assays in interleukin (IL)-1β-induced OA chondrocytes. The mechanistic contribution of EZH2, miR-142-3p, and HMGB1 to chondrocyte ER stress and pyroptosis and therapeutic prospects were validated radiologically, histologically, and immunohistochemically in surgically induced OA rats. RESULTS: Increased EZH2 and HMGB1, decreased miR-142-3p, enhanced ER stress, and activated pyroptosis in chondrocytes were associated with OA occurrence and progression. EZH2 and HMGB1 exacerbated and miR-142-3p alleviated ER stress and pyroptosis in OA chondrocytes. EZH2 transcriptionally silenced miR-142-3p via H3K27 trimethylation, and miR-142-3p posttranscriptionally silenced HMGB1 by targeting the 3'-UTR of the HMGB1 gene. Moreover, ER stress mediated the effects of EZH2, miR-142-3p, and HMGB1 on chondrocyte pyroptosis. In vivo experiments mechanistically validated the hierarchical regulatory relationship between EZH2, miR-142-3p, and HMGB1 and their effects on chondrocyte ER stress and pyroptosis. CONCLUSIONS A novel EZH2/miR-142-3p/HMGB1 axis mediates chondrocyte pyroptosis and cartilage degeneration by regulating ER stress in OA, contributing novel mechanistic insights into OA pathogenesis and providing potential targets for future therapeutic research.
Enhancer of Zeste Homolog 2 Protein/genetics* ; Osteoarthritis, Knee/pathology* ; Chondrocytes/metabolism* ; Pyroptosis/physiology* ; HMGB1 Protein/genetics* ; MicroRNAs/metabolism* ; Endoplasmic Reticulum Stress/genetics* ; Humans ; Animals ; Rats ; Male ; Rats, Sprague-Dawley ; Middle Aged

OBJECTIVE: To investigate the impact of bone mass and volume of low-density zones beneath the tibial plateau on the maximum von Mises stresses experienced by the cartilage and meniscus in the knee joint. METHODS: The study included one healthy adult volunteer, from whom CT scans were obtained, and one patient diagnosed with knee osteoarthrisis (KOA), for whom X-ray films were acquired. A static model of the knee joint featuring a low-density zone was established based on a normal knee model. In the finite element analysis, axial loads of 1 000 N and 1 800 N were applied to the weight-bearing region of the upper surface of the femoral head for model validation and subsequent finite element studies, respectively. The maximum von Mises stresses in the femoral cartilage, as well as the medial and lateral tibial cartilage and menisci, were observed, and the stress percentage of the medial and lateral components were concurrently analyzed. Additionally, HE staining, as well as alkaline magenta staining, were performed on the pathological specimens of patients with KOA in various low-density regions. RESULTS: The results of model validation indicated that the model was consistent with normal anatomical structures and correlated with previous calculations documented in the literature. Static analysis revealed that the maximum von Mises stress in the medial component of the normal knee was the lowest and increased with the advancement of the hypointensity zone. In contrast, the lateral component exhibited an opposing trend, with the maximum von Mises stress in the lateral component being the highest and decreasing as the hypointensity zone progressed. Additionally, the medial component experienced an increasing proportion of stress within the overall knee joint. HE staining demonstrated that the chondrocyte layer progressively deteriorated and may even disappear as the hypointensity zone expanded. Furthermore, alkaline magenta staining indicated that the severity of microfractures in the trabecular bone increased concurrently with the expansion of the hypointensity zone. CONCLUSION The presence of subtalar plateau low-density zone may aggravate joint degeneration. In clinical practice, it is necessary to pay attention to the changes in the subtalar plateau low-density zone and actively take effective measures to strengthen the bone status of the subtalar plateau low-density zone and restore the complete biomechanical function of the knee joint, in order to slow down or reverse the progression of osteoarthritis.
Humans ; Finite Element Analysis ; Knee Joint/physiology* ; Tibia/anatomy & histology* ; Cartilage, Articular/physiology* ; Menisci, Tibial/physiopathology* ; Tomography, X-Ray Computed ; Osteoarthritis, Knee/diagnostic imaging* ; Weight-Bearing ; Bone Density ; Adult ; Stress, Mechanical ; Male ; Middle Aged ; Biomechanical Phenomena ; Female

OBJECTIVE: To investigate the load distribution on the more painful and less painful limbs in patients with mild-to-moderate and severe bilateral knee osteoarthritis (KOA) and explore the compensatory mechanisms in both limbs among bilateral KOA patients with different severity levels. METHODS: A total of 113 participants were enrolled between July 2022 and September 2023. This cohort comprised 43 patients with mild-to-moderate bilateral KOA (Kellgren-Lawrence grade 2-3), 43 patients with severe bilateral KOA (Kellgren-Lawrence grade 4), and 27 healthy volunteers (healthy control group). The visual analogue scale (VAS) score for pain, the Hospital for Special Surgery (HSS) score, passive knee range of motion (ROM), and hip-knee-ankle angle (HKA) were used to assess walking pain intensity, joint function, and lower limb alignment in KOA patients, respectively. Motion trajectories of reflective markers and ground reaction force data during walking were captured using a gait analysis system. Musculoskeletal modeling was then employed to calculate biomechanical parameters, including the peak knee adduction moment (KAM), KAM impulse, peak joint contact force (JCF), and peak medial/lateral contact forces (MCF/LCF). Statistical analyses were performed to compare differences in clinical and gait parameters between bilateral limbs. Additionally, one-dimensional statistical parametric mapping was utilized to analyze temporal gait data. RESULTS: Mild-to-moderate KOA patients showed the significantly higher HSS score (67.7±7.9) than severe KOA patients (51.9±8.9; t=8.747, P<0.001). The more painful limb in all KOA patients exhibited significantly greater HKA and higher VAS scores compared to the less painful limb ( P<0.05). While bilateral knee ROM did not differ significantly in mild-to-moderate KOA patients ( P>0.05), the severe KOA patients had significantly reduced ROM in the more painful limb versus the less painful limb ( P<0.05). Healthy controls showed no significant bilateral difference in any biomechanical parameters ( P>0.05). All KOA patients demonstrated longer stance time on the less painful limb ( P<0.05). Critically, severe KOA patients exhibited significantly higher peak KAM, KAM impulse, and peak MCF in the more painful limb ( P<0.05), while mild-to-moderate KOA patients showed the opposite pattern with lower peak KAM and KAM impulse in the more painful limb ( P<0.05) and a similar trend for peak MCF. CONCLUSION Patients with mild-to-moderate KOA effectively reduce load on the more painful limb through compensatory mechanisms in the less painful limb. Conversely, severe bilateral varus deformities in advanced KOA patients nullify compensatory capacity in the less painful limb, paradoxically increasing load on the more painful limb. This dichotomy necessitates personalized management strategies tailored to disease severity.
Humans ; Osteoarthritis, Knee/physiopathology* ; Range of Motion, Articular ; Male ; Female ; Middle Aged ; Biomechanical Phenomena ; Knee Joint/physiopathology* ; Pain Measurement ; Severity of Illness Index ; Aged ; Gait/physiology* ; Walking/physiology* ; Case-Control Studies ; Adult ; Weight-Bearing

OBJECTIVE: To establish a finite element model of the knee joint based on coronal plane alignment of the knee (CPAK) typing method, and analyze the biomechanical characteristics of different types of knee joints. METHODS: The finite element models of the knee joint were established based on CT scan data of 6 healthy volunteers. There were 5 males and 1 female with an average age of 24.2 years (range, 23-25 years). There were 3 left knees and 3 right knees. According to the CPAK typing method, the knees were rated as types Ⅰ to Ⅵ. Under the same material properties, boundary conditions, and axial loading, biomechanical simulations were performed on the finite element model of the knee joint. Based on the Von Mises stress nephogram and displacement nephogram, the peak stresses of the meniscus, femoral cartilage, and tibial cartilage, and the displacement of the meniscus were compared among different types of knee joints. RESULTS: The constructed finite element model of the knee joint was verified to be effective, and the stress and displacement results were consistent with previous literature. Under the axial load of 1 000 N, the stress nephogram showed that the stress distribution of the medial and lateral meniscus and tibial cartilage of CPAK type Ⅲ knee joint was the most uneven. The peak stresses of the lateral meniscus and tibial cartilage were 9.969 6 MPa and 2.602 7 MPa, which were 173% and 165% of the medial side, respectively. The difference of peak stress between the medial and lateral femoral cartilage was the largest in type Ⅳ knee joint, and the medial was 221% of the lateral. The displacement nephogram showed that the displacement of the medial meniscus was greater than that of the lateral meniscus except for types Ⅲ and Ⅵ knee joints. The difference between medial and lateral meniscus displacement of type Ⅲ knee joint was the largest, the lateral was 170% of the medial. CONCLUSION In the same type of joint line obliquity (JLO), the medial and lateral stress distribution of the knee was more uniform in varus and neutral positions than in valgus position. At the same time, the distal vertex of JLO subgroup can help to reduce the uneven medial and lateral stress distribution of varus knee, but increase the uneven distribution of valgus knee.
Humans ; Finite Element Analysis ; Knee Joint/diagnostic imaging* ; Female ; Biomechanical Phenomena ; Adult ; Male ; Young Adult ; Stress, Mechanical ; Weight-Bearing/physiology* ; Computer Simulation ; Tomography, X-Ray Computed/methods* ; Cartilage, Articular/physiology* ; Range of Motion, Articular ; Menisci, Tibial/anatomy & histology* ; Tibia/anatomy & histology* ; Meniscus/diagnostic imaging* ; Femur/diagnostic imaging* ; Models, Biological

Objective To evaluate the effects of anterior cruciate ligament (ACL) reconstruction timing on the motor performance and proprioception by clinical evaluation as well as proprioception and motor performance tests on the patients more than 2 years after ACL reconstruction. Methods The patients who underwent ACL reconstruction in the National Institute of Sports Medicine,General Administration of Sport of China from January 2015 to January 2021 and met the inclusion criteria were followed up,and the postoperative data were collected retrospectively.Fifty-six patients who met the inclusion criteria were included in this study and categorized into two groups:early surgery (n=28,who underwent ACL reconstruction ≤3 weeks after injury) and delayed surgery (n=28,who underwent ACL reconstruction >3 weeks after injury).The basic information,clinical evaluation results,proprioception,and motor performance were compared between the two groups. Results The ACL return to sport after injury scale (ACL-RSI) score in the early surgery group was higher than that in the delayed surgery group [(68.68±22.04)scores vs. (55.82±24.87)scores,P=0.045].There was no difference in the range of motion of the knee joint,the positive rate of pivot shift test,or the scores of Tegner,Marx,Lysholm,knee injury and osteoarthritis outcome score (KOOS),and international knee documentation committee (IKDC) between the two groups (all P>0.05).Although there was no significant difference in range of motion of the knee joint between the two groups,the proportion of knee flexion and extension affected in the early surgery group was smaller than that in the delayed surgery group.Neither motor performance (isokinetic strength test,Y-balance test,and single-leg jump test) nor proprioception had difference between the two groups (all P>0.05). Conclusions Early ACL reconstruction outperformed delayed ACL reconstruction in improving the psychological health,emotions,and confidence in returning to sport,accelerating functional recovery of the patients.The timing of ACL reconstruction has no significant effect on the short-term postoperative knee stability,knee function,motor performance,or proprioceptive recovery of the patients.Early ACL reconstruction is recommended for improving the clinical outcomes.
Humans ; Anterior Cruciate Ligament Reconstruction/methods* ; Proprioception/physiology* ; Retrospective Studies ; Male ; Female ; Range of Motion, Articular ; Anterior Cruciate Ligament Injuries/physiopathology* ; Adult ; Postoperative Period ; Time Factors ; Return to Sport ; Recovery of Function ; Knee Joint/physiopathology* ; Young Adult

Objective To evaluate the effects of knee flexor and extensor strength on the subjective function and motor performance of knees after anterior cruciate ligament reconstruction. Methods A total of 53 patients who underwent anterior cruciate ligament reconstruction in the National Institute of Sports Medicine,General Administration of Sport of China from June 2015 to June 2021 and met the inclusion criteria were enrolled in this study.The patients were followed up time for at least 2 years.An isometric muscle strength test system was used to measure the strength of bilateral quadriceps and hamstring muscles.The patients were grouped according to whether the limb symmetry index (LSI) of peak torque of quadriceps and hamstring muscle reached 85% at an angular velocity of 60°/s.Specifically,26 patients were classified into group A (LSI≥85%) and 27 patients were classified into group B (LSI<85%).The subjective function and motor performance of knees were compared between the two groups. Results In terms of subjective function of knees,the international knee documentation committee (IKDC) score (88.76±9.93 vs. 81.08±12.57,P=0.017) and knee injury and osteoarthritis outcome score (KOOS) (86.27±8.96 vs. 80.22±11.31,P=0.036) were different between groups A and B.There was no significant difference in Lysholm score [95.0 (79.8,100.00) vs. 86.00 (66.00,100.00),P=0.238],ACL return to sports after injury scale score (66.08±22.25 vs. 61.12±23.53,P=0.434),Marx score [6.00 (4.75,7.00) vs. 6.00 (4.00,7.00),P=0.805] or Tegner activity score [8.00 (4.00,12.00) vs. 4.00 (2.00,12.00),P=0.566] between the two groups.In terms of motor performance,the single-leg triple hop LSI (0.92±0.13 vs. 0.81±0.18,P=0.016) and single-leg crossover hop LSI (0.96±0.12 vs. 0.84±0.22,P=0.021) showed significant differences between groups A and B,while there was no significant difference in single-leg hop LSI (0.90±0.18 vs. 0.79±0.25,P=0.116) between the two groups.In addition,there was no statistical significance in proprioception [30°:8.83±4.66 vs. 10.73±4.63,P=0.143;45°:6.94±3.82 vs. 7.66±3.93,P=0.504;60°:4.10 (3.20,4.72) vs. 3.90 (2.30,5.20),P=0.493] or Y-balance test results [anterior LSI:0.98 (0.84,1.02) vs. 0.94 (0.86,0.98),P=0.328;posterolateral LSI:1.00±0.08 vs. 0.97±0.07,P=0.249;posteromedial LSI:1.00 (0.97,1.03) vs. 0.96 (0.93,1.03),P=0.179] between groups A and B. Conclusion The patients with good symmetry of quadriceps and hamstring muscle strength after anterior cruciate ligament reconstruction had better subjective function and movement performance of knees than the patients with poor symmetry,which was mainly reflected in the IKDC score,KOOS,single-leg triple hop,and single-leg crossover hop.
Humans ; Anterior Cruciate Ligament Reconstruction ; Muscle Strength/physiology* ; Male ; Quadriceps Muscle/physiology* ; Female ; Adult ; Anterior Cruciate Ligament Injuries/physiopathology* ; Hamstring Muscles/physiopathology* ; Knee Joint/physiopathology* ; Anterior Cruciate Ligament/physiopathology* ; Torque ; Knee/physiopathology*

Objective To investigate the effects of rotation stability after anterior cruciate ligament reconstruction (ACLR) on subjective outcomes,sport performance,psychological readiness,and return to sport. Methods The patients who underwent ACLR in the Sports Hospital,National Institute of Sports Medicine,General Administration of Sport of China from January 2015 to January 2021 were followed up during the period from November 2022 to December 2023.The patients were grouped according to the results of the pivot shift test (PST) of the affected knee at the last follow-up visit.A total of 66 patients who participated in the follow-up and met the inclusion and exclusion criteria were finally enrolled in this study,including 32 patients showing a negative PST result (stable group) and 34 patients showing a positive PST result (unstable group).The basic information,subjective function score,and return-to-sport performance were compared between the two groups. Results In terms of sport performance,the two groups showed differences in the limb symmetry index in single-leg hops,triple hops,and crossover hops (P=0.028,P=0.024,and P=0.044,respectively).The anterior cruciate ligament-return to sport after injury scale score was higher in the stable group than in the unstable group [(70.44±22.82) scores vs. (53.44±21.74) scores,P=0.003].The mean of KT-2000 test results in the stable group was lower than that in the unstable group [(0.53±1.02) mm vs. (2.06±2.31) mm,P=0.001].The Lysholm score,international knee documentation committee score,knee injury and osteoarthritis outcome score,Tegner score,and Marx score did not have significance between the two groups (all P>0.05).The return-to-sport rate was 43.8% (including 14.3% reaching safe return criteria,which accounted for 6.3% in all the patients) in the stable group and 35.3% (including 8.3% reaching safe return criteria,which accounted for 2.9% in all the patients) in the unstable group.There was no difference in the 60°/s isokinetic muscle strength,maximal muscle strength ratio of the affected extensor-flexor muscles,or Y-balance test result between the two groups (all P>0.05). Conclusions Knee joint rotational instability after ACLR results in poor performance in single-leg hops,triple hops,and crossover hops,low psychological readiness,and anterior-posterior knee laxity.In short- to medium-term follow-up for ACLR,the return-to-sport rate remained low regardless of knee joint rotational stability,with the majority of patients failing to meet safe return criteria.
Humans ; Anterior Cruciate Ligament Reconstruction/rehabilitation* ; Male ; Female ; Knee Joint/surgery* ; Athletic Performance/physiology* ; Anterior Cruciate Ligament Injuries/physiopathology* ; Adult ; Joint Instability/physiopathology* ; Return to Sport ; Rotation ; Young Adult

Iliotibial band syndrome (ITBS), as an overused injury of the lower extremities, has developed into a common cause of lateral knee pain. At present, the treatment of ITBS includes drug therapy, muscle strength training, physical therapy, and surgical treatment. Among these methods, physical therapy, drug therapy, and surgical treatment can only alleviate the symptoms of patients. As a safe and effective treatment, lower limb muscle strength training can improve patients' muscle strength, correct abnormal gait, and reduce the recurrence rate of the disease by paying attention to the dynamic changes of patients' recovery process. At present, the pathogenesis of ITBS remains unclear, and the treatment methods are not unified. It is necessary to further study the biomechanical factors related to the lower extremities and develop more scientific and comprehensive muscle strength training methods.
Humans ; Resistance Training ; Running/physiology* ; Iliotibial Band Syndrome/diagnosis* ; Lower Extremity ; Physical Therapy Modalities/adverse effects* ; Knee Joint ; Muscle Strength/physiology* ; Muscles/injuries* ; Biomechanical Phenomena

A novel structural dynamics test method and device were designed to test the biomechanical effects of dynamic axial loading on knee cartilage and meniscus. Firstly, the maximum acceleration signal-to-noise ratio of the experimental device was calculated by applying axial dynamic load to the experimental device under unloaded condition with different force hammers. Then the experimental samples were divided into non-specimen group (no specimen loaded), sham specimen group (loaded with polypropylene samples) and bovine knee joint specimen group (loaded with bovine knee joint samples) for testing. The test results show that the experimental device and method can provide stable axial dynamic load, and the experimental results have good repeatability. The final results confirm that the dynamic characteristics of experimental samples can be distinguished effectively by this device. The experimental method proposed in this study provides a new way to further study the biomechanical mechanism of knee joint structural response under axial dynamic load.
Animals ; Cattle ; Biomechanical Phenomena ; Knee Joint/physiology* ; Meniscus ; Mechanical Phenomena ; Weight-Bearing

OBJECTIVE: To explore relationship between intramuscular fat content of quadriceps femoris and clinical severity of knee osteoarthritis (KOA). METHODS: Totally 30 KOA patients were selected from February 2021 to June 2021, including 6 males and 24 females, aged with an average of (64.20±9.19) years old, and body mass index (BMI) was (24.92±3.35) kg·m-2. Patients were divided into relative severe leg (RSL) and relative moderate leg (RML) according to severity of pain on visual analogue scale(VAS). Musculoskeletal ultrasound was used to collect muscle images of quadriceps muscles on both sides of the patient, and Image J was used to analyze echo intensity (EI) of each muscle. Both VAS and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were used to assess pain and function. Quadriceps muscle EI on both sides of patients was compared. Pearson correlation analysis was conducted to analyze correlation between quadriceps muscle EI value between RSL and RML, and linear regression was used to analyze relationship between each muscle EI and VAS and WOMA scores of patients. RESULTS: The EI of RSL lateral vastus lateralis (VL) was 123.78±36.25 and RSL vastus medialis (VM) was 109.46±30.36 which were significantly higher than those of 108.03±31.34 and 93.32±26.04 of RML (P<0.05), but there was no statistical significance in EI values of rectus femoris (RF) on both sides (P>0.05). EI values of VL and VM on both sides were significantly correlated (P<0.05). There was a significant positive correlation between VM EI value and VAS score in RSL and RML (P<0.05). VM EI values in RSL were positively correlated with total WOMAC (P<0.05), and VM VL EI values in RML were positively correlated with total WOMAC score (P<0.05). CONCLUSION Intramuscular fat content of quadriceps is closely related to severity of clinical symptoms in KOA patients, and the most obvious one is VM. Therefore, the intramuscular fat content of quadriceps may be an objective indicator to evaluate severity of KOA patients. At the same time, reducing intramuscular fat content of the quadriceps muscle of KOA patients may be a new direction for the prevention and treatment of KOA.
Male ; Female ; Humans ; Aged ; Middle Aged ; Quadriceps Muscle/physiology* ; Osteoarthritis, Knee/diagnosis* ; Pain ; Body Mass Index ; Muscle Strength/physiology* ; Knee Joint