Long-term effects of non-weight bearing and immobilization after anterior cruciate ligament reconstruction on joint contracture formation in rats.

PURPOSE: Non-weight bearing improves and immobilization worsens contracture induced by anterior cruciate ligament reconstruction (ACLR), but effect persistence after reloading and remobilization remains unclear, and the combined effects of these factors on ACLR-induced contracture are unknown. We aimed to determine 1) whether the effects of short-term (2-week) non-weight bearing or immobilization after ACLR on contracture would be sustained by reloading or remobilization during a 10-week observation period, and 2) how the combination of both interventions compared to the outcome of either alone. METHODS: We divided 88 ACL-reconstructed male rats into four groups: non-intervention, non-weight bearing, joint immobilization, and both interventions. Interventions were performed for 2 weeks, followed by rearing without intervention. Twelve untreated rats were used as controls. At 2, 4, and 12 weeks post-surgery, we assessed range of motion (ROM) and histological changes. RESULTS: ACLR resulted in persistent loss of ROM, accompanied by synovial shortening, capsule thickening, and osteophyte formation. Two weeks of non-weight bearing increased ROM and reduced osteophyte size, but the beneficial effects disappeared within 10 weeks after reloading. Two-week immobilization decreased ROM and facilitated synovial shortening. After remobilization, ROM partially recovered but remained below non-intervention levels at 12 weeks. When both interventions were combined, ROM was similar to immobilization alone. CONCLUSIONS: The beneficial effects of 2-week non-weight bearing on contracture diminished within 10 weeks after reloading. The adverse effects of 2-week immobilization on contracture persisted after 10 weeks of remobilization. The effects of the combined use of both interventions on contracture were primarily determined by immobilization.

The effects of the amount of weight bearing on articular cartilage early after ACL reconstruction in rats.

PURPOSE: Osteoarthritis that develops after anterior cruciate ligament (ACL) reconstruction is a critical issue. We examined the effects of the amount of weight bearing early after ACL reconstruction on articular cartilage. MATERIALS AND METHODS: Rats were divided into groups according to the treatment received: untreated control, ACL reconstruction (ACLR), ACL reconstruction plus hindlimb unloading (ACLR + HU), and ACL reconstruction plus morphine administration (ACLR + M). ACL reconstruction was performed on the right knee throughout the groups. To assess the amount of weight bearing, one-hindlimb standing time ratio (STR; operated side/contralateral side) during treadmill locomotion was evaluated during the experimental period. At day 7 or 14 post-surgery, cartilage degeneration of the medial tibial plateau was histologically assessed. RESULTS: In the ACLR group, reduction in weight bearing characterized by significantly reduced STR was observed between day 1 and 7. Reduction in weight bearing was partially attenuated by morphine administration. Compared with the control group, the ACLR group exhibited an increased Mankin score that was accompanied by increased cyclooxygenase-2 expression in the anterior region. In the ACLR + HU group, Mankin scores were significantly higher in the middle and posterior regions, and cartilage thickness in these regions was significantly thinner than those in the ACLR group. In the ACLR + M group, although chondrocyte density in the anterior region was increased, all other parameters were not significantly different from those in the ACLR group. CONCLUSIONS: Our results suggest that early weight bearing after ACL reconstruction is important to reduce cartilage degeneration.

The effects of weight bearing after ACL reconstruction on joint contracture in rats.

PURPOSE: Joint contractures after anterior cruciate ligament (ACL) reconstruction are a serious problem. Given the uncertain effects of weight bearing after ACL reconstruction on contractures, this study was conducted to examine such effects. MATERIALS AND METHODS: To control the amount of weight bearing, ACL-reconstructed rats were reared with either untreated (small weight bearing; weight bearing during locomotion was 54% of pre-surgery at minimum), hindlimb unloading (non-weight bearing), or sustained morphine administration (large weight bearing; weight bearing during locomotion was maintained at 80% or more of pre-surgery) conditions. Untreated rats were used as controls. Knee extension range of motions (ROMs) before (includes myogenic and arthrogenic factors) and after myotomy (includes arthrogenic factor only) and fibrotic reactions in the joint capsule were assessed 7 and 14 days post-surgery. RESULTS: ACL reconstruction significantly reduced ROMs both before and after myotomy and induced fibrosis in the joint capsule accompanying upregulation of fibrosis-related genes (i.e., type I and III collagens and transforming growth factor-ß1) at both time points. Morphine administration increased the ROM before myotomy, but not after myotomy 7 days post-surgery. Unloading after ACL reconstruction improved ROMs both before and after myotomy at both time points. In addition, unloading after ACL reconstruction attenuated fibrotic reactions in the joint capsule. CONCLUSIONS: Our results suggest that morphine administration improves myogenic contractures in parallel with an increase in the amount of weight bearing. Unloading after ACL reconstruction is effective in reducing both myogenic and arthrogenic contractures.

Effects of Gluteus Maximus Muscle Activity and Pelvic Width on Dynamic Frontal Plane Hip Joint Stiffness During Gait in Healthy Young Women.

CONTEXT: Excessive hip adduction and internal rotation are abnormal movements that may lead to the onset and progression of patellofemoral pain. Previous studies have reported that lower dynamic frontal plane hip joint stiffness in the gait of women is associated with the magnitude of hip adduction and internal rotation angles. However, the factors contributing to the lack of dynamic frontal plane hip joint stiffness in the gait of young women are unclear. This study aims to investigate the factors affecting dynamic frontal plane hip joint stiffness during the weight-acceptance phase of the gait of healthy young women. DESIGN: Cross-sectional study. METHODS: This study included 30 healthy women between the ages of 18 and 30 years. The pelvic width/femur length ratio was calculated by dividing the pelvic width by the femur length. Data on hip kinematics and kinetics and activation of the gluteus maximus and medius, tensor fasciae latae, and adductor longus muscles during gait were collected using a motion capture system, force plates, and surface electromyography. Stepwise multiple regression analysis was conducted to determine the extent to which each independent factor affected dynamic frontal plane hip joint stiffness. RESULTS: In healthy young women, decreased dynamic frontal plane hip joint stiffness was associated with decreased muscle activity of the gluteus maximus during the gait, as well as greater pelvic width/femur length ratio. CONCLUSIONS: Women with a relatively great pelvic width relative to femur length may have more difficulty in producing dynamic frontal plane hip joint stiffness. However, increasing the muscle activity of the gluteus maximus may contribute to increased dynamic frontal plane hip joint stiffness.

A rat model of arthrofibrosis developed after anterior cruciate ligament reconstruction without rigid joint immobilization.

Purpose: Complications including arthrofibrosis have been reported after anterior cruciate ligament reconstruction (ACLR) even under accelerated rehabilitation. To overcome this, we developed an animal model of ACLR-induced arthrofibrosis without immobilization.Materials and Methods: Thirteen male Wistar rats were divided into ACL transection (ACLT) and ACLR groups. Surgery was performed in the right knees and untreated left knees were used as controls. After surgery, rats could move freely without joint immobilization.Results: One week after surgery, flexion contracture represented by passive ROM reduction was 49 ± 5° and 21 ± 6° in ACLR and ACLT groups, respectively. Thereafter, flexion contractures were gradually reduced to 21 ± 8° and 12 ± 6° after 12 weeks, respectively. Fibrosis, which is characterized by significant upregulation of fibrosis-related genes, thickening, and adhesion in the posterior joint capsule, was observed in the ACLR group after 12 weeks of surgery. Nociceptive behavior and joint swelling were more apparent in the ACLR group than in the ACLT group, especially after 1 week of surgery.Discussions: We developed a rat model of ACLR-induced joint contracture due to arthrofibrosis without rigid immobilization. Joint contracture was also observed in the ACLT group, but to a considerably milder degree than in the ACLR group. Thus, signs of inflammation as a result of reconstruction surgery, rather than ACL transection, play an important role in the formation of joint contracture after ACLR. Our animal model is suited to examine the mechanisms and efficacy of therapeutic strategies for arthrofibrosis following ACLR treated without rigid joint immobilization.

Nitric oxide synthase inhibitor L-NG-nitroarginine methyl ester (L-NAME) attenuates remobilization-induced joint inflammation.

Shortly after joint remobilization, inflammation is induced in the joint and aggravates joint contracture via subsequent fibrosis. However, the mechanisms involved in remobilization-induced inflammation are not yet fully understood. We hypothesized that joint immobilization followed by remobilization induces hypoxia/reoxygenation, initiating inflammatory reactions through nitric oxide (NO) production via NO synthase 2 (NOS2). This study aimed to investigate whether: 1) administration of the NOS inhibitor L-NG-nitroarginine methyl ester (l-NAME) can attenuate remobilization-induced joint inflammation; and 2) hypoxia/reoxygenation is induced by joint immobilization and followed by remobilization. Unilateral knee joints of rats were immobilized using external fixators for three weeks. After removal of the fixation device, knees were allowed to move freely for one day (remobilization) with or without l-NAME administration. Without l-NAME administration, inflammatory reactions including joint swelling and inflammatory cell infiltration, edema, and upregulation of inflammatory mediator genes in the joint capsule were detected following upregulation of the NOS2 gene after remobilization. These remobilization-induced inflammatory reactions were partially attenuated by administration of l-NAME. Therefore, NOS2/NO elevation has potential as a novel treatment for remobilization-induced joint inflammation. Gene expression of the hypoxia marker hypoxia inducible factor-1α was upregulated after one day of remobilization, rather than after immobilization. These results suggest that upregulation of NOS2 by remobilization might be not due to hypoxia/reoxygenation.

Relationship Between Hip Frontal Dynamic Joint Stiffness and Frontal and Transverse Plane Hip Kinematics During Gait: Sex Differences.

CONTEXT: Previous studies have reported that the incidence of patellofemoral pain in women is 2.2 times higher than that in men. Lower hip frontal dynamic joint stiffness in women may be related to the magnitude of hip adduction and internal rotation associated with patellofemoral pain. OBJECTIVE: To identify sex differences in hip frontal dynamic joint stiffness and examine the relationship between hip frontal dynamic joint stiffness and hip adduction and internal rotation during gait. DESIGN: Cross-sectional study. SETTING: University campus. PARTICIPANTS: A total of 80 healthy volunteers (40 women and 40 men) participated in this study. INTERVENTION(S): Kinematic and kinetic data during gait were collected using a motion capture system and force plates. MAIN OUTCOME MEASURES: Hip frontal dynamic joint stiffness, hip adduction, and hip internal rotation were calculated during gait. RESULTS: Women demonstrated lower hip frontal dynamic joint stiffness than men during gait (P < .01). They also displayed decreased hip frontal dynamic joint stiffness associated with increased hip adduction (r = -.85, P < .001) and internal rotation (r = -.48, P < .001). Conversely, in men, decreased hip frontal dynamic joint stiffness was associated with increased hip adduction (r = -.74, P < .001) but not internal rotation (r = .17, P = .28). CONCLUSIONS: Sex differences between hip frontal dynamic joint stiffness and hip internal rotation during gait may contribute to the increased incidence of patellofemoral pain in women.

Effects of hypertonia on contracture development in rat spinal cord injury.

STUDY DESIGN: Experimental animal study. OBJECTIVES: Spastic hypertonia is originally believed to cause contractures from clinical observations. Botulinum toxin is effective for the treatment of spasticity and is widely used in patients who have joints with contractures. Using an established rat model with knee contractures after spinal cord injuries, we aimed to verify whether hypertonia contributes to contracture development, and the botulinum toxin improves structural changes in muscles and joint components responsible for contractures. SETTING: University laboratory in Japan. METHODS: To evaluate the effect of hypertonia on contracture development, the rats received botulinum toxin injections after spinal cord injuries. Knee extension motion was measured with a goniometer applying a standardized torque under anesthesia, and the contribution by muscle or non-muscle structures to contractures were calculated by measuring joint motion before and after the myotomies. We quantitatively measured the muscle atrophy, muscle fibrosis, and synovial intima length. RESULTS: Botulinum toxin injections significantly improved contractures, whereas did not completely prevent contracture development. Botulinum toxin was effective in improving the muscular factor, but little difference in the articular factor. Spinal cord injuries induced muscle atrophy, and botulinum toxin significantly accelerated muscle atrophy and fibrosis. The synovial intima length decreased significantly after spinal cord injuries, and botulinum toxin did not improve this shortening. CONCLUSIONS: This animal study provides new evidence that hypertonia is not the sole cause rather is the partial contributor of contractures after spinal cord injuries. Furthermore, botulinum toxin has adverse effects in the muscle.

Mechanical Stress by Spasticity Accelerates Fracture Healing After Spinal Cord Injury.

Accelerated fracture healing in patients with spinal cord injuries (SCI) is often encountered in clinical practice. However, there is no distinct evidence in the accelerated fracture healing, and the mechanisms of accelerated fracture healing in SCI are poorly understood. We aimed to determine whether SCI accelerated fracture healing in morphology and strength, to characterize the healing process with SCI, and to clarify the factors responsible for accelerated fracture healing. In total, 39 male Wistar rats were randomly divided into healthy control without intervention, SCI only, fracture with SCI, botulinum toxin (BTX) A-treated fracture with SCI, and propranolol-treated fracture with SCI groups. These rats were assessed with computed microtomography, histological, histomorphological, immunohistological, and biomechanical analyses. Both computed microtomography and histological analyses revealed the acceleration of a bony union in animals with SCI. The strength of the healed fractures after SCI recovered to the same level as that of intact bones after SCI, while the healed bones were weaker than the intact bones. Immunohistology revealed that SCI fracture healing was characterized by formation of callus with predominant intramembranous ossification and promoting endochondral ossification. The accelerated fracture healing after SCI was attenuated by BTX injection, but did not change by propranolol. We demonstrated that SCI accelerate fracture healing in both morphology and strength. The accelerated fracture healing with SCI may be due to predominant intramembranous ossification and promoting endochondral ossification. In addition, our results also suggest that muscle contraction by spasticity accelerates fracture healing after SCI.

Clinical Prediction Rule for Declines in Activities of Daily Living at 6 Months After Surgery for Hip Fracture Repair.

OBJECTIVES: To develop and assess a clinical prediction rule (CPR) to predict declines in activities of daily living (ADL) at 6 months after surgery for hip fracture repair. DESIGN: Prospective, cohort study. SETTING: From hospital to home. PARTICIPANTS: Patients (N=104) with hip fractures after surgery. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: ADL were assessed using the Barthel Index at 6 months after surgery. RESULTS: At 6 months after surgery, 86 patients (82.6%) were known to be alive, 1 patient (1.0%) had died, and 17 (16.3%) were lost to follow-up. Thirty-two patients (37.2%) did not recover their ADL at 6 months after surgery to levels before fracture. The classification and regression trees methodology was used to develop 2 models to predict a decline in ADL: (1) model 1 included age, type of fracture, and care level before fracture (sensitivity=75.0%, specificity=81.5%, positive predictive value=70.6%, positive likelihood ratio=4.050); and (2) model 2 included the degree of independence 2 weeks postsurgery for ADL chair transfer, ADL ambulation, and age (sensitivity=65.6%, specificity=87.0%, positive predictive value=75.0%, positive likelihood ratio=5.063). The areas under the receiver operating characteristic curves of both CPR models were .825 (95% confidential interval, .728-.923) and .790 (95% confidence interval, .683-.897), respectively. CONCLUSIONS: CPRs with moderate accuracy were developed to predict declines in ADL at 6 months after surgery for hip fracture repair.

Effects of exercise therapy on walking ability in individuals with knee osteoarthritis: a systematic review and meta-analysis of randomised controlled trials.

OBJECTIVE: To examine the effect of exercise therapy on the walking ability of individuals with knee osteoarthritis. DATA SOURCES: Randomised clinical trials (RCTs) were identified by searching through PubMed, Cochrane Central Register of Controlled Trials, Physiotherapy Evidence Database, and Cumulative Index to Nursing and Allied Health Literature. All literature published to October 2014 were included in the search. REVIEW METHODS: Data were collected from RCTs that compared the effects of exercise therapy on walking ability with the effects of no intervention or psychoeducational intervention in participants with knee osteoarthritis. The outcome data on the total distance walked (6-minute walk test); the amount of time spent walking (the time to walk arbitrary distances); and gait velocity were obtained and analysed. Standardized mean differences (SMDs) and 95% confidence intervals (CIs) were calculated. RESULTS: Twenty-eight RCTs were identified. Meta-analysis provided very-low-quality evidence that exercise therapy increased the total distance walked in the 6-minute walk test, in comparison with the effects of the control interventions (SMD = 0.44, 95% CI 0.27 to 0.60). Meta-analysis also provided low- or moderate-quality evidence that the amount of time spent walking and gait velocity were improved more by exercise therapy than by the control interventions (the amount of time spent walking: SMD = -0.50, 95% CI -0.70 to -0.30; gait velocity: SMD = 1.78, 95% CI 0.98 to 2.58). CONCLUSION: In individuals with knee osteoarthritis, exercise therapy can improve the amount of time spent walking, gait velocity, and maybe the total distance walked.

Cyclooxygenase-2 inhibitor celecoxib attenuates joint contracture following immobilization in rat knees.

BACKGROUND: The aim of this study is to clarify the following two points: First, whether a cyclooxygenase-2 mediated pathway is involved in the formation of immobilization-induced joint contracture and, second, the effectiveness of oral administration of non-steroidal anti-inflammatory drug celecoxib (CBX) for the prevention of myogenic and arthrogenic contracture following immobilization in a rat model. METHODS: Thirty male rats were randomly divided into three groups: immobilization (Im), Im + CBX, and control (n = 10 each). External fixation immobilized the right knee joint of Im and Im + CBX groups in flexion for 3 weeks. 50 mg/kg of CBX was administrated daily to the Im + CBX group during this period. The passive range of motion (ROM) of knee joints was measured before and after transection of knee flexor muscles and myogenic and arthrogenic ROM restrictions were calculated. The semitendinosus muscles and knee joints were investigated histologically to elucidate factors responsible for contracture. RESULTS: Myogenic ROM restrictions were exhibited both in Im and Im + CBX groups (44 ± 5 and 36 ± 8 °, respectively), but restrictions significantly decreased in the Im + CBX group compared to the Im group. Significant reductions of the muscle length ratios (Rt/Lt) and sarcomere number ratios (Rt/Lt) in knee flexor semitendinosus muscle, which are responsible for myogenic contracture, were also seen both in Im group (92 ± 5 and 92 ± 4 %, respectively) and Im + CBX group (97 ± 3 and 97 ± 3 %, respectively), but were inhibited by CBX administration (P < 0.05). Im and Im + CBX groups exhibited arthrogenic ROM restrictions with no significant differences (82 ± 3 and 83 ± 5 °, respectively). Posterior synovial length shortening and pathological changes (hemorrhage in joint cavities and capsule edema) in the knee joints were comparable between Im and Im + CBX groups. CONCLUSIONS: Oral administration of celecoxib partially reduced myogenic ROM restriction concomitantly with knee flexor muscle shortening following immobilization. These results imply that inflammation and nociception are involved in myogenic contracture formation independently of joint immobilization, and that CBX is effective in preventing joint contracture following immobilization in rats.

Does exercise therapy improve the health-related quality of life of people with knee osteoarthritis? A systematic review and meta-analysis of randomized controlled trials.

[Purpose] The aim of this study was to examine the effects of exercise therapy on the health-related QOL of people with knee osteoarthritis. [Subjects] Four databases (PubMed, Cochrane Central Register of Controlled Trials, the Physiotherapy Evidence Database, and the Cumulative Index to Nursing and Allied Health Literature) were searched for randomized controlled trials that evaluated the effects of exercise therapy on health-related QOL assessed by the SF-36 for inclusion in our systematic review. The methodological qualities of the trials were assessed independently by two reviewers using the PEDro scale. Pooled analyses with a random-effects model or a fixed-effects model were used in the meta-analyses to calculate the standardized mean differences and 95% confidence intervals. [Results] Twelve studies met the inclusion criteria. Our meta-analysis provides high-quality evidence that exercise therapy increases the summary score, physical functioning score, and role-physical score of knee osteoarthritis sufferers. Our meta-analysis also provides moderate-quality evidence that the physical component summary and mental component summary scores were improved to a greater extent by exercise therapy than by control interventions. [Conclusion] Exercise therapy can improve health-related QOL, as assessed by the SF-36, of knee osteoarthritis sufferers.

Intermittent whole-body vibration attenuates a reduction in the number of the capillaries in unloaded rat skeletal muscle.

BACKGROUND: Whole-body vibration has been suggested for the prevention of muscle mass loss and muscle wasting as an attractive measure for disuse atrophy. This study examined the effects of daily intermittent whole-body vibration and weight bearing during hindlimb suspension on capillary number and muscle atrophy in rat skeletal muscles. METHODS: Sixty male Wistar rats were randomly divided into four groups: control (CONT), hindlimb suspension (HS), HS + weight bearing (WB), and HS + whole-body vibration (VIB) (n = 15 each). Hindlimb suspension was applied for 2 weeks in HS, HS + WB, and HS + VIB groups. During suspension, rats in HS + VIB group were placed daily on a vibrating whole-body vibration platform for 20 min. In HS + WB group, suspension was interrupted for 20 min/day, allowing weight bearing. Untreated rats were used as controls. RESULTS: Soleus muscle wet weights and muscle fiber cross-sectional areas (CSA) significantly decreased in HS, HS + WB, and HS + VIB groups compared with CONT group. Both muscle weights and CSA were significantly greater in HS + WB and HS + VIB groups compared with HS group. Capillary numbers (represented by capillary-to-muscle fiber ratio) were significantly smaller in all hindlimb suspension-treated groups compared with CONT group. However, a reduction in capillary number by unloading hindlimbs was partially prevented by whole-body vibration. These findings were supported by examining mRNA for angiogenic-related factors. Expression levels of a pro-angiogenic factor, vascular endothelial growth factor-A mRNA, were significantly lower in all hindlimb suspension-treated groups compared with CONT group. There were no differences among hindlimb suspension-treated groups. Expression levels of an anti-angiogenic factor, CD36 (receptor for thrombospondin-1) mRNA, were significantly higher in all hindlimb suspension-treated groups compared with CONT group. Among the hindlimb suspension-treated groups, expression of CD36 mRNA in HS + VIB group tended to be suppressed (less than half the HS group). CONCLUSIONS: Our results suggest that weight bearing with or without vibration is effective for disuse-derived disturbance by preventing muscle atrophy, and whole-body vibration exercise has an additional benefit of maintaining microcirculation of skeletal muscle.

Effect of the Frequency and Duration of Land-based Therapeutic Exercise on Pain Relief for People with Knee Osteoarthritis: A Systematic Review and Meta-analysis of Randomized Controlled Trials.

[Purpose] This study aimed to investigate the influence of land-based exercise frequency and duration on pain relief for people with knee osteoarthritis (OA). [Subjects and Methods] The systematic review included randomized controlled trials that investigated this influence, which were identified by searches of PubMed, the Cochrane Central Register of Controlled Trials, the Physiotherapy Evidence Database, and the Cumulative Index to Nursing and Allied Health Literature. The exercise groups in the identified trials were categorized according to their type, frequency, and duration of exercise, and subgroup analyses were performed. [Results] Data integration of 17 studies (23 exercise groups) revealed a significant effect and a medium effect size. In subgroups involving strengthening exercise programs of ≥9 weeks duration, heterogeneity was found between subjects who performed up to 3 sessions/week and those who performed ≥4 sessions/week. In subgroups involving strengthening exercise programs of up to 3 sessions/week, there was heterogeneity between subjects who exercised for up to 8 weeks and those who exercised for ≥9 weeks. Heterogeneity was not confirmed in aerobic exercise subgroups. [Conclusion] Differences in exercise frequency and duration influence pain relief in effects of strengthening exercises but do not influence the effect size of aerobic exercise for people with knee OA.

Effects of Weight Bearing on Marrow Adipose Tissue and Trabecular Bone after Anterior Cruciate Ligament Reconstruction in the Rat Proximal Tibial Epiphysis.

The effects of mechanical unloading after anterior cruciate ligament (ACL) reconstruction on bone and marrow adipose tissue (MAT) are unclear. We investigated weight bearing effects on bone and MAT after ACL reconstruction. Rats underwent unilateral knee ACL transection and reconstruction, followed by hindlimb unloading (non-weight bearing), no intervention (low-weight bearing, the hindlimb standing time ratio (STR; operated/contralateral) during treadmill locomotion ranging from 0.55 to 0.91), or sustained morphine administration (moderate-weight bearing, STR ranging from 0.80 to 0.95). Untreated rats were used as controls. At 7 or 14 days after surgery, changes in trabecular bone and MAT in the proximal tibial were assessed histologically. Histological assessments at 7 or 14 days after surgery showed that ACL reconstruction without post-operative intervention did not significantly change trabecular bone and MAT areas. Hindlimb unloading after ACL reconstruction induced MAT accumulation with adipocyte hyperplasia and hypertrophy within 14 days, but did not significantly affect trabecular bone area. Increased weight bearing through morphine administration did not affect trabecular bone and MAT parameters. Our results suggest that early weight bearing after ACL reconstruction is important in reducing MAT accumulation, and that reduction in weight bearing alone is not sufficient to induce bone loss early after ACL reconstruction.

The Effects of Corticosteroid Administration and Treadmill Exercise on Marrow Adipose Tissue and Trabecular Bone after Anterior Cruciate Ligament Reconstruction in Rats.

We aimed to investigate the effects of short-term corticosteroid administration after anterior cruciate ligament (ACL) reconstruction on marrow adipose tissue (MAT) and trabecular bone mass, as well as to examine whether treadmill exercise can mitigate MAT increase and trabecular bone deterioration caused by corticosteroid. ACL-reconstructed rats were divided into groups: no intervention, daily treadmill exercise (60 min/day), administration of the steroidal drug dexamethasone (250 µg/kg on days 0-5, 7, and 9 post-operatively), or dexamethasone administration combined with treadmill exercise. Untreated rats were served as controls. At day 10 or 30 post-operatively, histological assessments were performed in the proximal tibial epiphysis. MAT accumulation and trabecular bone loss were observed after ACL reconstruction. Dexamethasone promoted MAT accumulation at day 10 post-operatively but did not affect the trabecular bone loss. The MAT accumulation caused by dexamethasone reversed within 21 days after discontinuation. Treadmill exercise did not influence the changes in the MAT and trabecular bone areas. Short-term corticosteroid administration after ACL reconstruction promoted MAT accumulation while not affecting trabecular bone area. The MAT accumulation resulting from corticosteroid administration was reversible after discontinuation. Treadmill exercise could not mitigate the accumulation of MAT caused by corticosteroid administration and did not affect trabecular bone area.

Sex differences in pelvis, thigh, and shank coordination during walking.

Differences in lower limb kinematics between males and females during functional activities may be attributed to sex differences in the incidence of patellofemoral pain, which is more common in females. To better comprehend the knee joint motion, it is necessary to understand both inter-segmental coordination patterns and angular amplitude. This exploratory study aimed to assess sex differences in pelvis-thigh and thigh-shank coordination patterns in the frontal and horizontal planes during walking. Data regarding the kinematic characteristics of the pelvis, thigh, and shank segments were collected from 26 males and 26 females performing walking at self-selected speeds using a 3D motion capture system. Furthermore, we compared the kinematics of the pelvis, thigh, and shank during walking as well as the pelvis-thigh and thigh-shank coordination patterns in the frontal and horizontal planes during the stance phase between males and females. Compared to males, females had greater thigh adduction (p < 0.001) and internal rotation (p < 0.001) throughout the stance phase; significantly greater frequency of the pelvis-thigh anti-phase pattern in the frontal plane in the early (p = 0.002) and mid-stance (p = 0.003); and significantly greater thigh-shank anti-phase pattern in the frontal plane in the early (p = 0.001) and mid-stance (p = 0.015). These results suggest the presence of sex differences in the inter-segmental coordination of the pelvis and lower limb during walking. However, as this study could not determine a causal relationship between female sex and knee joint injury, further longitudinal studies are needed to determine the effects of differences in coordination patterns on the pathophysiology of the injury and pain generation.

Development of patellofemoral osteoarthritis with knee joint malalignment and lateral patellar dislocation after hindlimb suspension in growing rats.

Knee malalignment is a risk factor for patellar instability and patellofemoral osteoarthritis (PFOA), but etiologies remain unknown. We investigated the potential effects of decreased weight loading during growth on knee alignments and patellofemoral (PF) joint pathology. Hindlimb suspension (HS) was performed in 4-week-old female rats for 2, 4, and 8 weeks (HS groups). Age-matched rats were used as controls. Three-dimensional reconstructed images of the knee were obtained using X-ray computed tomography. Tibial tubercle-trochlear groove (TT-TG) distance, patellar tilt angle, and bisect offset were measured as indices of knee alignment. Histological analysis was also performed to evaluate the changes in cartilage and synovium in the PF joints. At Week 8, TT-TG distance, patella tilt angle, and bisect offset were significantly larger in the HS group than in the control group, respectively, indicating tibial external rotation, outward patellar tilt, and external displacement of the patella. Lateral patellar dislocation was frequently found in the HS group at Week 8 (five of eight knee joints, p < 0.05). Degenerative changes in the cartilage of the trochlear groove were observed at Week 8, and synovial changes such as hypertrophy and synovitis were observed at Weeks 4 and 8. Correlation analyses revealed significant relationships between the Mankin score and bisect offset, and between the OARSI synovitis score and all knee alignments indices. These results suggest that decreased weight loading on the lower extremities in growing rats resulted in knee malalignments characterized by external rotation of tibia and high incidence of lateral patellar dislocation with concomitant PFOA.

Effects of sex differences on osteoarthritic changes after anterior cruciate ligament reconstruction in rats.

The prevalence of primary osteoarthritis is higher in females than males. However, it remains unclear if there are sex differences in the incidence of post-traumatic osteoarthritis after anterior cruciate ligament (ACL) reconstruction. In this study, we aimed to investigate the effects of sex on osteoarthritic changes after ACL reconstruction using an animal model. Rats were divided into the following four groups: male control, male ACL reconstruction, female control, and female ACL reconstruction. ACL reconstruction surgery was performed on the right knees of rats in the ACL reconstruction groups, while rats in the control groups did not undergo knee surgery. At 1, 4, and 12 weeks after surgery, cartilage degeneration in the medial tibial plateau and osteophyte formation in the proximal tibia were histologically assessed. After ACL reconstruction, an increase in the Mankin score, cartilage fissures, and osteophyte formation were detected within 12 weeks in both male and female rats, with similar degrees of these changes between males and females. However, changes in cartilage thickness and chondrocyte density after ACL reconstruction differed between males and females. Cartilage thickening was observed in male rats but not in female rats. The increase in chondrocyte density in the anterior region was detected in both males and females but was more pronounced in female rats. In conclusion, osteoarthritic changes were observed after ACL reconstruction in both male and female rats, but differences in changes in cartilage thickness and chondrocyte density were observed between males and females.