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AimsJoint instability is associated with various joint conditions including osteoarthritis (OA) and inflammation, and we have developed model which is determined to role of knee instability. Investigating cartilage maintenance factors such as hyaluronic acid (HA) and glycosaminoglycans (GAGs) can provide insights into the effect of the mechanical stress and the inhibitor used, with the following aims: 1) whether cartilage degeneration is inhibited in the new model, 2) whether combination TGF-β1 inhibition mitigates cartilage degeneration, and to determine the role of TGF-β1 in synovitis using fibroblasts.Main methodsWe used this novel model to investigate inhibition of OA progression with a focus on HA and GAGs, which help maintain the cartilage and synovial membrane. In detail, mechanical tests, X-ray, histological, and protein and mRNA expression analyses were used to determine the role of joint stability using in vivo model or fibroblast from synovial membrane.Key findingsJoint stability mitigated cartilage degeneration loss, decreased osteophytes, increased the expression levels of HA and GAGs in the synovial membrane, and decreased the release of pro-inflammatory factors in rats. Moreover, injection of TGF-β1 inhibitor in an inflammatory synovial membrane promoted HA and GAGs expression. In synovial fibroblast cells, inhibition of TGF-β1 over expression significantly inhibited the downregulation of pro-inflammatory factors and promoted the upregulation of lubrification for cartilage.SignificanceOur results suggest that joint instability is an independent mechanical factor for OA progression. The results provide novel insights into the association between OA and joint instability, which has significant human sciences implications.Research Highlights• Established a new experimental rat model of the different joint instability for elucidate osteoarthritis onset/progression• Using Histological staining to investigated the osteoarthritis including synovitis and osteophytes of the novel model• Using fibroblast from synovial membrane to investigated the fibrosis• Joint instability exacerbates articular cartilage degeneration and decreases HA and GAGs protein expressions in synovial membrane• TGF-β1 inhibitor on early osteoarthritis joints may suppress synovial inflammation

Motor function recovery is frequently poor after peripheral nerve injury. The effect of different numbers of nerve crushes and exercise on motor function recovery is unknown. We aimed to examine how different numbers of crushes of the rat sciatic nerve affects muscle reinnervation and plasticity of spinal circuits and the effect of exercise intervention.Single and multiple sciatic nerve crush models with different numbers of crushes were created in rats. Treadmill exercise was performed at 10 m/min for 60 min, five times a week. Muscle reinnervation and synaptic changes in L4-5 motor neurons were examined by immunofluorescence staining. Behavioral tests were the sciatic functional index (SFI) and the pinprick tests.The percentage of soleus muscle reinnervation was not significantly increased by the presence of exercise in single or multiple crushes. Exercise after a single crush increased the contact of motor neurons with VGLUT1-containing structures (Exercised vs. Unexercised, 12.9% vs. 8.7%; p .01), but after multiple crushes, it decreased with or without exercise (8.1% vs. 8.6%). Exercise after a single crush significantly improved SFI values from 14 to 24 days, and exercise after multiple crushes from 21 to 35 days (all p .05). The pinprick test showed no difference in recovery depending on the number of crushes or whether or not exercised.Different numbers of sciatic nerve crushes affect muscle reinnervation and motor neuron synaptic changes differently, but motor function recovery may improve with exercise regardless of the number of crushes.

The foot arch plays an important role in propulsion and shock absorption during walking and running; however, the relationship among the foot arch, metatarsal locking theory, and nature of the windlass mechanism (WM) remain unclear.What are the differences in the kinematic relationship between the foot arch, hindfoot, and hallux during walking and running?Relative angles within the foot were measured in 18 healthy men using the Oxford foot model (OFM). Data for barefoot walking at a comfortable speed and rearfoot running at 2.0 m/s were collected. Angles of the forefoot relative to the hindfoot (OFM-arch), hallux relative to the forefoot (Hallux) on the sagittal plane, and hindfoot relative to the shank (Hindfoot) on three anatomical planes were obtained. The medial longitudinal arch (MLA) angle was calculated to verify that OFM-arch can substitute the MLA angle. Each parameter was subjected to cross-correlation analysis and Wilcoxon signed-rank tests to examine the relationship with OFM-arch and compare them during walking and running.OFM-arch was similar to the conventional MLA projection angle in both trials (gait: 0.79, running: 0.96 p 0.01). Synchronization of the OFM-arch and Hallux angles was higher in running than in walking (gait: -0.09, running: -0.75 p 0.01). Hindfoot supination was unrelated to OFM-arch. Hindfoot angle on the transverse plane exhibited a moderate relationship with OFM-arch, indicating different correlations in walking and running (gait: 0.63, running: -0.68 p 0.01).The elevation of the foot arch due to hallux dorsiflexion differed during walking and running; hence, other factors besides WM (such as intrinsic muscles) may affect the foot arch elevation during running. The hindfoot in the frontal plane does not contribute to arch raising and foot stability during running; it features different relationships with OFM-arch during walking and running.

Mechanical stress is involved in the onset of sports-related enthesopathy. Although the amount of exercise undertaken is a recognized problem during disease onset, changes in muscle contraction type are also involved in the increase in mechanical stress during exercise. This study aimed to clarify the effects of increased mechanical stress associated with muscle contraction type and amount of exercise on enthesis. Twenty mice underwent treadmill exercise, and the muscle contraction type and overall load during exercise were adjusted by varying the angle and speed conditions. Histological analysis was used to the cross-sectional area of the muscle; area of the enthesis fibrocartilage (FC), and expression of inflammation-, degeneration-, and calcification-related factors in the FC area. In addition, the volume and structure of the bone and FC area were examined using microcomputer imaging. Molecular biological analysis was conducted to compare relative expression levels of inflammation and cytokine-related factors in tendons. The Overuse group, which increased the amount of exercise, showed no significant differences in parameters compared to the sedentary mice (Control group). The mice subjected to slow-speed downhill running (Misuse group) showed pathological changes compared to the Control and Overuse groups, despite the small amount of exercise. Thus, the enthesis FC area may be altered by local mechanical stress that would be increased by eccentric muscle contraction rather than by mechanical stress that increases with the overall amount of exercise. Clinical Significance: The muscle contraction type might be more involved in the onset of sports-related enthesopathy rather than the amount of exercise.

Background Although the importance of kinematic evaluation of the sit-to-stand (STS) test of total knee arthroplasty (TKA) patients is clear, there have been no reports analyzing STS during the 30-s chair sit-up test (30 s-CST) with a focus on kinematic characteristics. This study aimed to demonstrate the clinical utility of kinematic analysis of STS during the 30 s-CST by classifying STS into subgroups based on kinematic parameters, and to determine whether differences in movement strategies are expressed as differences in clinical outcomes. Methods The subjects were all patients who underwent unilateral TKA due to osteoarthritis of the knee and were followed up for one year postoperatively. Forty-eight kinematic parameters were calculated using markerless motion capture by cutting STS in the 30 s-CST. The principal components of the kinematic parameters were extracted and grouped by kinematic characteristics based on the principal component scores. Clinical significance was examined by testing whether differences in patient-reported outcome measures (PROMs) were observed. Results Five principal components were extracted from the 48 kinematic parameters of STS and classified into three subgroups (SGs) according to their kinematic characteristics. It was suggested that SG2, using a kinematic strategy similar to the momentum transfer strategy shown in previous studies, performed better in PROMs and, in particular, may be associated with achieving a “forgotten joint”, which is considered the ultimate goal after TKA. Conclusions Clinical outcomes differed according to kinematic strategies used STS, suggesting that kinematic analysis of STS in 30 s-CST may be useful in clinical practice. Trial registration This study was approved by the Medical Ethical Committee of the Tokyo Women’s Medical University (approval number: 5628 on May 21, 2021).

Purpose Joint instability is a common joint dysfunction and a cause of musculoskeletal disorder and pain after anterior cruciate ligament injury and osteoarthritis. The aim of this literature review is to review the existing evidence regarding the impacts of knee brace in persons with joint instability, or laxity after knee disease concerning physical and functional outcomes. Methods A systematic search was performed at MEDLINE, Central Register of Controlled Trials (CENTRAL), PubMed, and PEDro and Web of Science databases until April 2, 2022, with their language limited to English. Studies to be included were randomized controlled trials (RCTs), controlled clinical trials, and controlled experimental studies that included comparison of interventions and no interventions testing effectiveness of orthotics in joint instability symptom patients Results Total 250 studies were retrieved and 12 articles met the inclusion criteria. Beneficial effects of knee braces appear to vary with disease. Self-reported instability may be improved with orthotics, while its effects are unclear in an objective assessment of joint instability. However, improved subjective instability lead to improved physical function. Conclusion Our aim is to provide information to both healthcare professionals with updated and high-quality recommendations for the management of instability joint condition. It is concluded that orthotic therapy may have a certain effect on subjective evaluation in joint instability.

ObjectiveAs the progression of knee osteoarthritis (OA) is associated with large biomechanical loads, an optimally designed intervention is needed to prevent disease progression and symptoms. We aimed to investigate the effect of exercise therapy—the gold standard intervention—on biomechanical loads in patients with knee OA and identify its modification factors.DesignSystematic review and meta-analysisData sourcesPubMed, PEDro, and CINAHL; from study inception to May 2021Eligibility criteriaStudies evaluating the first peak knee adduction moment (KAM), peak knee flexion moment (KFM), maximal knee joint compression force (KCF), or co-contraction during walking before and after exercise therapy in patients with knee OARisk of BiasPEDro scale and NIH scale.ResultsAmong 11 RCTs and nine non-RCTs, 1100 patients with knee OA were included. First peak KAM (SMD 0.11; 95% CI: -0.03–0.24), peak KFM (SMD 0.13; 95% CI: -0.03–0.29), and maximal KCF (SMD 0.09; 95% CI -0.05–0.22) tended to increase. An increased first peak KAM was significantly associated with a larger improvement in knee muscle strength and WOMAC pain. The quality of evidence regarding the biomechanical loads was low-to-moderate according to the GRADE approach.ConclusionsExercise therapy tends to increase biomechanical loads. The improvement in pain and knee muscle strength may mediate the increase in first peak KAM, suggesting difficulty in balancing symptom relief and biomechanical load reduction. Therefore, exercise therapy may satisfy both aspects simultaneously when combined with biomechanical interventions, such as a valgus knee brace or insoles.FundingGrant-in-Aid for JSPS Research Fellows, 19J23020.RegistrationPROSPERO (CRD42021230966)

To determine the foot kinematics of the depth-jump in healthy adults. We examined the usefulness of a multi-segment foot model for a movement that requires impact absorption and force exertion on the foot. Twenty healthy adults (ten men, ten women) performed a depth-jump from a 40-cm height box on to force plates. We analyzed foot motion on the landing and jump preparation phases using the Rizzoli Foot Model. A pattern of foot motion was observed during the depth-jump. Although there were no differences of the foot structure at the static standing position with respect to sex, the maximum angle of the medial longitudinal arch (MLA) in the landing phase was significantly greater in women than in men (p = 0.017). The maximum angle of the MLA in the landing phase was strongly negatively correlated with the jump height (r = − 0.6, p = 0.05). By using a multi-segment foot model, it was possible to observe a common foot motion pattern among subjects, even during a quick movement such as the depth-jump. We suggest that motion analysis using the multi-segment foot model will be useful in evaluating the foot functions of impact absorption and force exertion during a dynamic movement such as the depth-jump.

During walking, the slip velocity relative to the center of mass velocity can be one of the determinants of falls. We hypothesized that participants would select their strategy (classified by strategy type and measured by the distance of recovery landing or next forward stepping) according to both walking velocity and stance of legs. This study aimed to assess the relationship between the walking velocity relative to the slip velocity (maximum 1.6 m/s) and the corrective response and evaluated the element of the posture at the moment of slipping associated with the corrective response. Ten healthy young adults showed leading leg perturbation in two isolated velocity conditions during over ground walking (slow: 0.9 m/s, fast: 1.6 m/s) using a built-in, double-belt treadmill. We defined the corrective response to perturbation as the change in the heel marker distance post-perturbation. We examined the postural parameters affecting the difference in corrective response. During fast walking, at a velocity near the maximum slip velocity, all participants overcame slipping and kept walking. During slow walking, at a velocity less than the maximum slip velocity, most of the participants took wide steps or stepped backwards and stopped walking. During slow walking, the step length (r = 0.84, p

ObjectiveThe effect of the type of mechanical stress on OA onset has not been clarified. The aim of this study was to establish a new model that reproduces the type and increase and decrease of mechanical stress in vivo and to clarify the differences in the mechanism of knee OA onset and progression among the models.DesignTo reproduce the difference in mechanical stress, we used the anterior cruciate ligament transection (ACL-T) model and the destabilization of the medial meniscus (DMM) model. In addition, we created a controlled abnormal tibial translation (CATT) model and a controlled abnormal tibial rotation (CATR) model that suppressed the joint instability of the ACL-T and DMM model, respectively. These four models reproduced the increase and decrease in shear force due to joint instability and compressive stress due to meniscal dysfunction. We performed joint instability analysis with soft X-ray, micro computed tomography analysis, histological analysis, and immunohistological analysis in 4 and 6 weeks.ResultsJoint instability decreased in the CATT and CATR groups. The meniscus deviated in the DMM and CATR groups. Chondrocyte hypertrophy increased in the ACL-T and DMM groups with joint instability. In the subchondral bone, bone resorption was promoted in the ACL-T and CATT groups, and bone formation was promoted in the DMM and CATR groups.ConclusionsIncreased shear force causes articular cartilage degeneration and osteoclast activation in the subchondral bone. In contrast, increased compressive stress promotes bone formation in the subchondral bone earlier than articular cartilage degeneration occurs.

Background Adaptation to split-belt treadmill walking differs between individual stroke survivors. Many discussions only address spatiotemporal parameters that are related to movement, and the changes in interlimb spatiotemporal parameters as a consequence of adaptation are poorly understood. Objectives To investigate symmetry of the center of pressure (CoP) position relative to the center of mass (CoM), and ascertain whether this can be used to identify differences in adaptation of interlimb spatiotemporal parameters among stroke survivors during split-belt walking. Methods Twenty-two chronic post-stroke patients and nine elderly controls walked in tied- then split-belt (2:1 ratio of fast:slow) conditions. Spatiotemporal parameters were compared within groups to assess symmetry of the CoM-CoP angle at foot contact. Results Asymmetry of the CoM-CoP angle was associated with asymmetry of spatiotemporal parameters. Re-establishment of symmetry of CoM-CoP angle was reflected in re-established symmetry of spatiotemporal parameters in post-stroke and control participants. Conclusions Post-stroke patients who re-establish symmetry of the COM-COP angle are able to adapt their walking for split-belt perturbation. This suggests that predictively symmetric foot placements on the fast and slow sides are necessary for adaptation in walking. Symmetrical foot placement is achieved by interlimb coordination and may contribute to dynamic stability.

Anterior cruciate ligament (ACL) injury is one of the most common injuries of the knee joint and is becoming more prevalent. While ACL reconstruction is considered the “gold standard” of treatment, some studies have demonstrated natural spontaneous healing of the ACL in humans, rabbits, and rats. At this time, the mechanism of ACL healing is poorly understood. The purpose of this study was to determine the process of ACL healing by examining the molecular and histological changes in the acute phases, using an ACL-Transection model and a spontaneous ACL healing model. Sixty adult male Wistar rats were randomly assigned to two groups: the ACL transection (ACLT) group and the controlled abnormal movement (CAM) group. Thirty rats were randomly assigned to three groups (day 1, day 3, and day 5). Then, all rats underwent an ACL transection procedure. The CAM group rats underwent controlled abnormal extra-articular tibial translation. Samples were harvested from rats and used for histological and biochemical analyses. Both, the ACLT and the CAM groups exhibited ruptured ACLs. However, in the CAM group, the ends of the proximal remnants were not retracted. Expressions of MMP-3 and PDGF-α increased, and expression of TGF-β1 decreased in the CAM group on day 5 (p

Objective Joint instability and meniscal dysfunction contribute to the onset and progression of knee osteoarthritis (OA). In the destabilization of the medial meniscus (DMM) model, secondary OA occurs due to the rotational instability and increases compressive stress resulting from the meniscal dysfunction. We created a new controlled abnormal tibial rotation (CATR) model that reduces the rotational instability that occurs in the DMM model. So, we aimed to investigate whether rotational instability affects articular cartilage degeneration using the DMM and CATR models, as confirmed using histology and immunohistochemistry. Design Twelve-week-old male mice were randomized into 3 groups: DMM group, CATR group, and INTACT group (right knee of the DMM group). After 8 and 12 weeks, we performed the tibial rotational test, safranin-O/fast green staining, and immunohistochemical staining for tumor necrosis factor (TNF)-α and metalloproteinase (MMP)-13. Results The rotational instability in the DMM group was significantly higher than that of the other groups. And articular cartilage degeneration was higher in the DMM group than in the other groups. However, meniscal degeneration was observed in both DMM and CATR groups. The TNF-α and MMP-13 positive cell rates in the articular cartilage of the CATR group were lower than those in the DMM group. Conclusions We found that the articular cartilage degeneration was delayed by controlling the rotational instability caused by meniscal dysfunction. These findings suggest that suppression of rotational instability in the knee joint may be an effective therapeutic measure for preventing OA progression.

Cartilage degeneration is the main pathological component of knee osteoarthritis (OA), but no effective treatment for its control exists. Although exercise can inhibit OA, the abnormal joint movement with knee OA must be managed to perform exercise. Our aims were to determine how controlling abnormal joint movement and treadmill exercise can suppress cartilage degeneration, to analyze the tissues surrounding articular cartilage, and to clarify the effect of treatment. Twelve-week-old ICR mice (n = 24) underwent anterior cruciate ligament transection (ACL-T) surgery on their right knees and were divided into three groups as follows: ACL-T, animals in the walking group subjected to ACL-T, controlled abnormal joint movement (CAJM), and CAJM with exercise (CAJM + Ex) (n = 8/group). Walking-group animals were subjected to treadmill exercise 6 weeks after surgery, including walking for 18 m/min, 30 min/day, 3 days/week for 8 weeks. Safranin-O staining, hematoxylin-eosin staining, and immunohistochemical staining were performed. The OARSI (Osteoarthritis research Society international) score was lower in the CAJM group than in the ACL-T group and was even lower in the CAJM + Ex group. The CAJM group had a lower meniscal injury score than the ACL-T group, and the CAJM + Ex group demonstrated a less severe synovitis than the ACL-T and CAJM groups. The observed difference in the perichondrium tissue damage score depending on the intervention method suggests different therapeutic effects, that normalizing joint motion can solve local problems in the knee joint, and that the anti-inflammatory effect of treadmill exercise can suppress cartilage degeneration.

The healing ability of the anterior cruciate ligament (ACL) injury is very poor; however, it has recently been shown to undergo self-healing with conservative treatments. In this study, we evaluated the influence of the site of injury on the healing process after complete transverse tear of ACL using a rat model.A total of 58 skeletally mature Wistar rats were randomly assigned to various ACL injury groups: controlled abnormal movement-mid-portion (CAM-MP), controlled abnormal movement-femoral side (CAM-FS), ACL transection-mid-portion (ACLT-MP), or ACL transection-femoral side (ACLT-FS) injury groups. The ACL was completely transected in the mid-portion in the ACLT-MP and CAM-MP groups, and on the femoral side in the ACLT-FS and CAM-FS groups. Both CAM groups underwent extra-articular braking to control for abnormal tibial translation. The animals were allowed full cage activity until sacrifice postoperatively for histological and biomechanical assessment.Significant differences were found in the ratios of residual ligament lengths between the CAM-MP and CAM-FS groups, demonstrating the validity of each model. Spontaneous healing of the injured ACL was observed in the CAM-MP and CAM-FS groups but not in the ACLT-MP and ACLT-FS groups. The mechanical strength of the healing ACL did not differ between the CAM-MP and CAM-FS groups 8 weeks after injury; however, the former had better mechanical strength than the latter 12 weeks after the injury.ACL injuries in the mid-portion and on the femoral side may be treated with conservative therapy for spontaneous healing.

Objective: To clarify whether there are any muscle synergy changes in individuals with knee osteoarthritis, and to determine whether muscle synergy analysis could be applied to other musculoskeletal diseases. Methods: Subjects in this study included 11 young controls (YC), 10 elderly controls (EC), and 10 knee osteoarthritis patients (KOA). Gait was assessed on a split-belt treadmill at 3 km/h. A non-negative matrix factorization (NNMF) was applied to the electromyogram data matrix to extract muscle synergies. To assess the similarity of each module, we performed the NNMF analysis assuming four modules for all of the participants. Further, we calculated joint angles to compare the kinematic data between the module groups. Results: The number of muscle modules was significantly lower in the EC (2–3) and KOA (2–3) groups than in the YC group (3–4), which reflects the merging of late swing and early stance modules. The EC and KOA groups also showed greater knee flexion angles in the early stance phase. Contrarily, by focusing on the module structure, we found that the merging of early and late stance modules is characteristic in KOA. Conclusion: The lower number of modules in the EC and KOA groups was due to the muscle co-contraction with increased knee flexion angle. Contrarily, the merging of early and late stance modules are modular structures specific to KOA and may be biomarkers for detecting KOA. Significance: Describing the changes in multiple muscle control associated with musculoskeletal degeneration can serve as a fundamental biomarker in joint disease.

Summary Objective Abnormal load stress caused by joint instability has been reported to be one of the factors responsible for the development of osteoarthritis (OA). However, few studies have investigated the efficacy of exercise therapy for patients with knee instability-induced OA, and there are no specific treatment guidelines or effects for this form of OA. Therefore, the purpose of this study was to examine the effect of exercise treatments for joint instability in patients with knee OA by a systematic review. Design Systematic review. Results Searches in three databases, PubMed, Cochrane, and the Physiotherapy Evidence Database, yielded 14 articles that were scrutinized, and 6 articles that met the inclusion criteria were selected. Conclusions Exercise therapy focusing on joint instability, including muscle maintenance and strength training, and specific training targeting knee instability have no additional beneficial effects on knee joint instability. However, because of the benefits of treatment protocols based on patient attributes in exercise treatment focused on joint instability, it is necessary to investigate the effects in more detail in the future.

People walking on a split-belt treadmill, where each belt moves at a different speed, adapt step length to re-establish symmetry. However, kinematic changes that occur when re-establishing step length symmetry have not yet been clarified. This study aims to clarify the changing lower limb joint kinematics of each leg when re-establishing step length symmetry. We examined ten young adults who walked on a double-belt treadmill under symmetric and asymmetric conditions of belt velocity using a motion capture system. The results showed that the hip flexion angle at heel strike on one side was not significantly different between the symmetric and asymmetric conditions (p = 0.38) thereby demonstrating that the hip flexion angle of the leading leg re-established symmetry at heel strike (HS) of the fast and slow sides. However, the knee extension angle of the leading leg expanded asymmetrically at HS on both sides. The shank of the fast leg possibly accelerated more to move the heel further forward. The results indicated that subjects with limited knee extension function must increase their hip flexion movement of the fast-side limb to accelerate the shank in the swing phase. The present study suggests securing the range of motion and treatment of the knee extension to reduce the spasticity of hamstrings or plantarflexor before split-belt training. Moreover, split-belt training may be undesirable for improving step length symmetry in impaired subjects who are unlikely to improve the function of knee extension movement. The present study contributes toward developing a rehabilitation protocol that improves the gait asymmetry of patients through split-belt training.

We developed a novel controlled abnormal joint movement (CAJM) model that controls instability after traditional anterior cruciate ligament transection (ACL-T). We evaluated whether joint instability damping suppresses synovial inflammation in osteoarthritis patients using our new CAJM rat model. We found that joint instability in rats differed between the ACL-T and CAJM models. Joint instability might contribute to synovitis and inhibit osteoarthritis.

Background The anterior cruciate ligament (ACL) is responsible for braking forward movement of the tibia relative to the femur and for tibial rotation. After ACL injury, this braking performance deteriorates, inducing abnormal joint movement. The purpose of this study was to clarify the effects of controlled abnormal joint movement on the molecular biological response in intra-articular tissues during the acute phase of ACL injury. Methods Eighty-four mature Wistar male rats were randomly assigned to a controlled abnormal movement (CAM) group, an ACL-transection (ACL-T) group, a sham-operated group, or an intact group. The ACL was completely transected at its midportion in the ACL-T and CAM groups, and a nylon suture was used to control abnormal tibial translation in the CAM group. The sham-operated group underwent skin and joint capsule incisions and tibial drilling without ACL transection. Animals were not restricted activity until sacrifice 1, 3, or 5 days after surgery for histological and gene expression assessments. Acute-phase inflammation requires an important balance between degenerative and biosynthetic processes and is controlled by the activities of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). Both types of gene were analyzed in this study. Results The ACL-T and CAM groups exhibited cleavage of the ACL at all time points. However, for the CAM group, the gap in the ligament stump was extremely small, and fibroblast proliferation was observed around the stump. Relative to the ACL-T group, the CAM group demonstrated significantly lower expression of MMP-13 mRNA and a lower MMP-13/TIMP-1 ratio on days 1 and 5 in the ACL, the medial meniscus and the lateral meniscus. The expression of TIMP-1 mRNA was not significantly different between the ACL-T and CAM groups. Conclusions The study results suggested that controlling abnormal movement inhibited the inflammatory reaction in intra-articular tissues after ACL injury. This reaction was down-regulated in intra-articular tissues in the CAM group. Abnormal joint control caused prolonged inflammation and inhibited remodeling during the acute phase of ACL rupture.

Background Physiological evidence suggests that the nervous system controls motion by using a low-dimensional synergy organization for muscle activation. Because the muscle activation produces joint torques, kinetic changes accompanying aging can be related to changes in muscle synergies. Objectives We explored the effects of aging on muscle synergies underlying sit-to-stand tasks, and examined their relationships with kinetic characteristics. Methods Four younger and three older adults performed the sit-to-stand task at two speeds. Subsequently, we extracted the muscle synergies used to perform these tasks. Hierarchical cluster analysis was used to classify these synergies. We also calculated kinetic variables to compare the groups. Results Three independent muscle synergies generally appeared in each subject. The spatial structure of these synergies was similar across age groups. The change in motion speed affected only the temporal structure of these synergies. However, subject-specific muscle synergies and kinetic variables existed. Conclusions Our results suggest common muscle synergies underlying the sit-to-stand task in both young and elderly adults. People may actively change only the temporal structure of each muscle synergy. The precise subject-specific structuring of each muscle synergy may incorporate knowledge of the musculoskeletal kinetics.

For clinicians to provide more efficient early mobilization in patients with acute stroke, they must quantitatively evaluate the motion characteristics of the patients. To measure the motion in the acute phase, it is necessary to prevent physical interference between the measurement and medical equipment. This study classified abnormal muscle synergies during sit-to-stand motion in patients with acute stroke by using small, wirelessly operable, noninvasive surface electromyography devices. Four patients with acute stroke and four healthy adults performed a six-directional isometric contraction task and a sit-to-stand motion task. A nonnegative matrix factorization algorithm was applied to the muscle activity data to extract the muscle synergies. Hierarchical cluster analysis was used to classify these synergies. The results suggest that sit-to-stand motion characteristics according to the severity of effects in patients with acute stroke can be quantitatively classified by muscle synergy analysis. The spatial structure of muscle synergies of patients was classified into different clusters from that of the healthy adults. The abnormal muscle synergy in patients with severe paresis is considered severe in that it cannot be modulated according to the task. The muscle synergies in patients with moderate paresis were modulated in the sit-to-stand motion to compensate for extensor muscle weakness. Such abnormal muscle synergy in the sit-to-stand motion is useful as a reference for motion practice, especially for early mobilization after the onset of a stroke. In addition, the results verify that the early to late stages of recovery can be consistently evaluated with this small, wireless noninvasive electromyography device.

Objective Osteoarthritis (OA) is induced by accumulated mechanical stress to joints; however, little has been reported regarding the cause among detailed mechanical stress on cartilage degeneration. This study investigated the influence of the control of abnormal joint movement induced by anterior cruciate ligament (ACL) injury in the articular cartilage. Design The animals were divided into 3 experimental groups: CAJM group ( n = 22: controlling abnormal joint movement), ACL-T group ( n = 22: ACL transection or knee anterior instability increased), and INTACT group ( n = 12: no surgery). After 2 and 4 weeks, the knees were harvested for digital microscopic observation, soft X-ray analysis, histological analysis, and synovial membrane molecular evaluation. Results The 4-week OARSI scores showed that cartilage degeneration was significantly inhibited in the CAJM group as compared with the ACL-T group ( P < 0.001). At 4 weeks, the osteophyte formation had also significantly increased in the ACL-T group ( P < 0.001). These results reflected the microscopic scoring and soft X-ray analysis findings at 4 weeks. Real-time synovial membrane polymerase chain reaction analysis for evaluation of the osteophyte formation–associated factors showed that the mRNA expression of BMP-2 and VEGF in the ACL-T group had significantly increased after 2 weeks. Conclusions Typically, abnormal mechanical stress induces osteophyte formation; however, our results demonstrated that CAJM group inhibited osteophyte formation. Therefore, controlling abnormal joint movement may be a beneficial precautionary measure for OA progression in the future.