Mechanisms of quadriceps muscle weakness in knee joint osteoarthritis: the effects of prolonged vibration on torque and muscle activation in osteoarthritic and healthy control subjects

There is more to the knee joint than just the quadriceps: A systematic review with meta-analysis and evidence gap map of hamstring strength, flexibility, and morphology in individuals with gradual-onset knee disorders

BACKGROUND

Impairments in hamstring strength, flexibility, and morphology have been associated with altered knee biomechanics, pain, and function. Determining the presence of these impairments in individuals with gradual-onset knee disorders is important and may indicate targets for assessment and rehabilitation. This systematic review aimed to synthesize the literature to determine the presence of impairments in hamstring strength, flexibility, and morphology in individuals with gradual-onset knee disorders.

METHODS

Five databases (MEDLINE, Embase, CINAHL, SPORTDiscus, and Web of Science) were searched from inception to September 2022. Only studies comparing hamstring outcomes (e.g., strength, flexibility, and/or morphology) between individuals with gradual-onset knee disorders and their unaffected limbs or pain-free controls were included. Meta-analyses for each knee disorder were performed. Outcome-level certainty was assessed using the Grading of Recommendations Assessment, Development, and Evaluation, and evidence gap maps were created.

RESULTS

Seventy-nine studies across 4 different gradual-onset knee disorders (i.e., knee osteoarthritis (OA), patellofemoral pain (PFP), chondromalacia patellae, and patellar tendinopathy) were included. Individuals with knee OA presented with reduced hamstring strength compared to pain-free controls during isometric (standard mean difference (SMD) = -0.76, 95% confidence interval (95%CI) : -1.32 to -0.21) and concentric contractions (SMD = -0.97, 95%CI : -1.49 to -0.45). Individuals with PFP presented with reduced hamstring strength compared to pain-free controls during isometric (SMD = -0.48, 95%CI : -0.82 to -0.14), concentric (SMD = -1.07, 95%CI : -2.08 to -0.06), and eccentric contractions (SMD = -0.59, 95%CI : -0.97 to -0.21). No differences were observed in individuals with patellar tendinopathy. Individuals with PFP presented with reduced hamstring flexibility when compared to pain-free controls (SMD = -0.76, 95%CI : -1.15 to -0.36). Evidence gap maps identified insufficient evidence for chondromalacia patellae and hamstring morphology across all gradual-onset knee disorders.

CONCLUSION

Our findings suggest that assessing and targeting impairments in hamstring strength and flexibility during rehabilitation may be recommended for individuals with knee OA or PFP.

Quadriceps recovery and pain relief in knee osteoarthritis rats by cog polydioxanone filament insertion

Quadriceps muscles play a pivotal role in knee osteoarthritis (OA) progression and symptom manifestation, particularly pain. This research investigates the therapeutic effectiveness of muscle enhancement and support therapy (MEST), a recently developed device intended for intramuscular insertion of cog polydioxanone filaments, in quadriceps restoration to alleviate OA pain. Knee OA was induced in Sprague Dawley rats via monoiodoacetate injections. MEST or sham treatment was performed in OA or Naive rat quadriceps. Pain was assessed using paw withdrawal threshold and weight bearing. Quadriceps injury and recovery via MEST were evaluated using biomarkers, tissue morphology, muscle mass, contractile force and hindlimb torque. Satellite cell and macrophage activation, along with their activators, were also assessed. Data were compared at 1- and 3-weeks post-MEST treatment (M-W1 and M-W3). MEST treatment in OA rats caused muscle injury, indicated by elevated serum aspartate transferase and creatinine kinase levels, and local β-actin changes at M-W1. This injury triggered pro-inflammatory macrophage and satellite cell activation, accompanied by heightened interleukin-6 and insulin-like growth factor-1 levels. However, by M-W3, these processes gradually shifted toward inflammation resolution and muscle restoration. This was seen in anti-inflammatory macrophage phenotypes, sustained satellite cell activation and injury markers regressing to baseline. Quadriceps recovery in mass and strength from atrophy correlated with substantial OA pain reduction at M-W3. This study suggests that MEST-induced minor muscle injury triggers macrophage and satellite cell activation, leading to recovery of atrophied quadriceps and pain relief in OA rats.

Towards a comprehensive biomechanical assessment of the elderly combining in vivo data and in silico methods

The aging process is commonly accompanied by a general or specific loss of muscle mass, force and/or function that inevitably impact on a person's quality of life. To date, various clinical tests and assessments are routinely performed to evaluate the biomechanical status of an individual, to support and inform the clinical management and decision-making process (e.g., to design a tailored rehabilitation program). However, these assessments (e.g., gait analysis or strength measures on a dynamometer) are typically conducted independently from one another or at different time points, providing clinicians with valuable yet fragmented information. We hereby describe a comprehensive protocol that combines both in vivo measurements (maximal voluntary isometric contraction test, superimposed neuromuscular electrical stimulation, electromyography, gait analysis, magnetic resonance imaging, and clinical measures) and in silico methods (musculoskeletal modeling and simulations) to enable the full characterization of an individual from the biomechanical standpoint. The protocol, which requires approximately 4 h and 30 min to be completed in all its parts, was tested on twenty healthy young participants and five elderlies, as a proof of concept. The implemented data processing and elaboration procedures allowing for the extraction of several biomechanical parameters (including muscle volumes and cross-sectional areas, muscle activation and co-contraction levels) are thoroughly described to enable replication. The main parameters extracted are reported as mean and standard deviation across the two populations, to highlight the potential of the proposed approach and show some preliminary findings (which were in agreement with previous literature).

A controlled randomized trial with a 12-week follow-up investigating the effects of medium-frequency neuromuscular electrical stimulation on pain, VMO thickness, and functionality in patients with knee osteoarthritis

BACKGROUND

One of the major contributors to disability in Knee osteoarthritis (KOA) patients is weakness in the Quadriceps Femoris muscle. Neuromuscular electrical stimulation (NMES) has been used in rehabilitation for patients suffering from muscle weakness. Thus, the purpose of the study was to assess the effectiveness of NMES and exercise therapy, for improving pain, muscle weakness and function among patients with KOA.

METHODS

A randomized controlled trial was conducted with 75 female patients diagnosed with KOA. Participants were divided into three intervention groups: NMES-only, exercise therapy (Exs) alone, and a combination of NMES and exercise (NMES + Exs). All patients underwent 12 supervised treatment sessions, three times a week. Outcome measures included pain intensity measured by visual analog scale (VAS), knee flexion range of motion (FROM), thigh muscle girth (TG), thickness of the Vastus Medialis Oblique (VMO), timed up and go test (TUG), six-minute walk test (6MWT), and WOMAC scores. Statistical analyses (ANOVA and Kruskal-Wallis) methods were done to compare the amounts at the baseline, immediately after treatment and after 12 weeks.

RESULTS

The NMES group exhibited a significant reduction in pain at the 12-week follow-up compared to the other groups(p = 0.022). The NMES + Exs group showed better outcomes in terms of FROM, TG, and VMO thickness post-intervention (p < 0.0001, p < 0.004, p = 0.003, respectively) and at the 12-week follow-up (p < 0.0001, p < 0.0001, p < 0.0001, respectively). Additionally, NMES was superior in improving TUG and 6MWT post-intervention (p < 0.0001, p = 0.038, respectively) and during the follow-up assessments (p < 0.0001, p = 0.029, respectively). The NMES + Exs group achieved better WOMAC stiffness scores at both post-intervention and follow-up evaluations (p < 0.0001, p < 0.0001, respectively). Furthermore, at the 12-week follow-up, NMES + Exs group outperformed the others in WOMAC pain and function subscales (p = 0.003, p = 0.017, respectively), while the NMES group demonstrated better WOMAC total scores compared to the other groups (p = 0.007).

CONCLUSION

The combination of NMES and exercise seems to be an efficient approach for managing KOA, as it enhances knee flexion range and TG, increases VMO thickness, and improves WOMAC scores. On the other hand, NMES alone was found to be effective in improving the physical function of KOA patients.

TRIAL REGISTRATION

IRCT20101228005486N7 (06-02-2020).

Effectiveness and mechanism of action of rTMS combined with quadriceps strength training in individuals with knee osteoarthritis: study protocol for a randomized controlled trial

BACKGROUND

Quadriceps training is necessary in function and activity of daily living for patients with knee osteoarthritis (KOA). However, it did not reduce the rate of surgical treatment for end-stage KOA in the long term. This may be related to brain structure changes and maladaptive plasticity in KOA patients. Transcranial Magnetic Stimulation (TMS) could enhance the functional connectivity of brain regions and improves maladaptive plasticity. However, the synergistic effect of the combination of the two for treat KOA is still unclear. Therefore, the purpose of this study is to investigate whether the High-Frequency rTMS combined with quadriceps strength training can improve the pain and function in KOA more effectively than quadriceps training alone and explore the mechanism of action.

METHODS

This study is an assessor-blind, sham-controlled, randomized controlled trial involving 12 weeks of intervention and 6 months follow-up. 148 participants with KOA will receive usual care management and be randomized into four subgroups equally, including quadriceps strength training, high-frequency rTMS training, sham rTMS and quadriceps strength training, high-frequency rTMS and quadriceps strength training. The rehabilitation interventions will be carried out 5 days per week for a total of 12 weeks. All outcomes will be measured at baseline, 4 weeks, 8 weeks, and 12 weeks during the intervention and 1 month, 3 months and 6 months during the follow-up period. The effectiveness outcomes will be included visual analog scale, isokinetic knee muscle strength, Knee Injury and Osteoarthritis Outcome score and 36-Item Short-Form Health Survey score; The act mechanism outcomes will be included motor evoked potential, grey matter density, white matter, subcortical nuclei volumes, cortical thickness and functional connectivity by MRI. Two-way of variance with repeated measures will be used to test the group and time effect for outcome measures.

DISCUSSION

The study will be the first protocol to examine whether there are synergistic effects following high-frequency rTMS combined with quadriceps strength training for treat KOA and clarify the mechanism of action. High-frequency rTMS can be added into the training program for KOA patients if it is proven effective.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR2300067617. Registered on Jan.13,2023.

Tactile stimulation restores inhibited stretch reflex attributable to attenuation of Ia afferents during surprise landing

Arthrogenic muscle inhibition (AMI) is induced by pathological knee conditions. The present study aimed to investigate the effect of tactile stimulation on reflex changes induced by simulated AMI during unpredictable landing performances. Twenty participants performed six unilateral landing tasks: 15 cm normal landing (15NL), 30 cm normal landing (30NL), surprise landing (SL), 30 cm normal landing following vibration (30NLV), SL following vibration (SLV), and SL following vibration with Kinesiology tape (SLK). For SL, the solid landing platform (15 cm) was removed and replaced by a false floor. Since the false floor dislodged easily under load, participants unpredictably fell through the platform to the actual landing surface 15 cm below. After completing 15NL, 30NL, and SL, vibration was applied to participants' knees to induce neurological changes similar to AMI. After vibration, participants performed 30NLV, SLV, and SLK in a random order. EMG signals in the post-landing short latency (31-60 ms) and medium latency (61-90 ms) periods were examined. EMG signals from the vastus lateralis (VL), vastus medialis (VM), and biceps femoris (BF) were recorded and compared between tasks. EMG signals of all muscles in SL were significantly enhanced in the medium latency period as compared with 30NL. Enhanced EMG signals in SL were suppressed by vibration stimulation in the VL, but the suppressed EMG signals were restored after cutaneous stimulation with Kinesiology tape (p < 0.01). Our findings suggest that AMI could alter motor control patterns during unpredictable landing and that tactile stimulation could restore the altered motor control to a normal state.

Association between quadriceps tendon elasticity and neuromuscular control in individuals with knee osteoarthritis

BACKGROUND

Knee osteoarthritis is a complex condition with established risk factors such as female sex, increasing age and body mass index, reduced quadriceps muscle strength and knee injury. Despite known associated risks, the role and behaviour of knee tendons in knee osteoarthritis remains unclear. This study explores the association between quadriceps tendon elasticity, muscle strength, neuromuscular control, proprioception and patient reported outcome measures in individuals with knee osteoarthritis.

METHODS

Adults with doctor-diagnosed knee osteoarthritis were recruited from rheumatology clinics and general practitioner practices. Quadriceps tendon elasticity was estimated using sonoelastography. Neuromuscular control data including electromyography, electromechanical delay and proprioception measures were included. Participants completed the Knee Injury and Osteoarthritis Outcome Score. Associations between elasticity values, physical and neuromuscular data and patient reported outcomes scores were evaluated using Spearman's correlations.

FINDINGS

Thirty-nine adults with knee osteoarthritis were eligible for inclusion. Increased tendon stiffness was negatively associated with rate of force development, time to half peak force and passive positioning sense in individuals with knee osteoarthritis. Similarly, patient reported symptoms were found to be associated with sonoelastography findings with moderate-strong associations observed between activities of daily living sport and recreation, pain and symptoms and between neuromuscular control measures and muscle strength.

INTERPRETATION

Stiffer tendon identified within the knee osteoarthritis group was associated with reduced neuromuscular control and knee joint proprioception. Stiffer quadriceps tendon may contribute to the poorer reported symptoms by knee osteoarthritis individuals. These findings may impact disease symptoms and progression which could lead to further joint impairment.

Joint pressure stimuli increase quadriceps strength and neuromuscular activity in patients with knee osteoarthritis

The study investigated the effects of periarticular knee pressure stimuli on quadriceps strength and neuromuscular activity in subjects with knee osteoarthritis. Twenty-five subjects with knee osteoarthritis and 25 age-matched healthy controls performed maximal voluntary knee extension tasks on an isometric dynamometer. Three different pressure stimuli (no-pressure, 60-mmHg, 120-mmHg) were applied using a sphygmomanometer via the cuff covering the knee joint. Peak torque and root-mean-square peak of rectus femoris (RF), vastus medialis (VM), and vastus lateralis (VL) were collected and normalized for the no-pressure condition (nTorque-peak and nRMS-peak). Normalized Torque-peak increased from no-pressure to 60-mmHg and 120-mmHg in patients, which revealed higher nTorque-peak during 60-mmHg (MD: 10.9%, IC95: 1.8%, 20.1%, p = 0.020) and 120-mmHg (MD: 16.0%, IC95: 4.4%, 27.6%, p = 0.008) conditions than healthy subjects. Moreover, nRMS-peak increased from no-pressure to 60-mmHg for RF, from no-pressure to 120-mmHg for RF, VM and VL, and from 60-mmHg to 120 mm-Hg for VL in patients. Patients revealed higher nRMS-peak of RF and VM during 60-mmHg and 120-mmHg conditions than healthy subjects. Periarticular knee pressure stimuli enhanced quadriceps strength and neuromuscular activity in subjects with knee osteoarthritis. This approach may represent a new strength training modality in patients with neuromuscular activation deficits for knee osteoarthritis.

Oligonucleotide Therapeutics for Age-Related Musculoskeletal Disorders: Successes and Challenges

Age-related disorders of the musculoskeletal system including sarcopenia, osteoporosis and arthritis represent some of the most common chronic conditions worldwide, for which there remains a great clinical need to develop safer and more efficacious pharmacological treatments. Collectively, these conditions involve multiple tissues, including skeletal muscle, bone, articular cartilage and the synovium within the joint lining. In this review, we discuss the potential for oligonucleotide therapies to combat the unmet clinical need in musculoskeletal disorders by evaluating the successes of oligonucleotides to modify candidate pathological gene targets and cellular processes in relevant tissues and cells of the musculoskeletal system. Further, we discuss the challenges that remain for the clinical development of oligonucleotides therapies for musculoskeletal disorders and evaluate some of the current approaches to overcome these.

Muscle activation patterns around knee following neuromuscular training in patients with knee osteoarthritis: secondary analysis of a randomized clinical trial

Objective

To compare the effects of neuromuscular training (NMT) to a quadriceps strength training (QT) program on co-contraction index (CCI) of knee muscles in patients with knee osteoarthritis (OA).

Methods

Sixty-six knee OA patients with varus malalignment were recruited from the physiotherapy outpatient department of the university. After baseline measurements, they were randomly assigned into two groups: NMT (n = 33) and QT (n = 33). Patients in NMT group received neuromuscular exercises whereas QT group received conventional strengthening exercises for a period of 12 weeks, three times per week. Electromyographic (EMG) activity of quadriceps, hamstring and gastrocnemius muscle was evaluated during treadmill walking before and after 12 weeks of intervention period and CCI of medial quadriceps-medial hamstring (med QH), lateral quadriceps-lateral hamstring (lat QH), medial quadriceps-medial gastrocnemius (med QG) and, lateral quadriceps and lateral gastrocnemius (lat QG) was calculated.

Results

There was a significantly greater reduction in CCI of med QH (p = 0.02) and lat QH (p = 0.01) in the NMT group than the QT group. Whereas both NMT and QT led to statistically similar reductions in CCI of med QG (p = 0.08) and lat QG (p = 0.66).

Conclusion

Findings of this study suggest that NMT led to a greater reduction in CCI of knee muscles than QT which indicates that enhanced sensori-motor control attained by NMT could reduce knee loading in knee OA patients with varus malalignment.

The effects of knee osteoarthritis on neural activity during a motor task: A scoping systematic review

OBJECTIVE

To examine the evidence of neural activation with functional magnetic resonance imaging (fMRI), corticospinal excitability, and other central nervous system measurement differences during motor tasks between those with and without knee osteoarthritis (KOA).

METHODS

A scoping review strategy was systematically performed. We searched PubMed, CINAHL, Embase, PsychInfo, SportDiscus, SCOPUS and Web of Science from database inception to April 2021. Any study investigating central nervous system measures during a motor task for individuals with KOA with or without a healthy control group for comparison was included. Two reviewers independently screened all studies in accordance with the Preferred Reported Items for Systematic Reviews and Meta-analyses extension for scoping reviews.

RESULTS

Thirteen studies met the inclusion criteria. KOA had reduced activation of the premotor cortex during a gait imagery task when examining the brain using fMRI. This hypoactivation was not significant when the task was combined with ankle movement. Individuals with KOA had decreased motor cortex activation during a force matching motor task. KOA was associated with gamma loop dysfunction of the quadriceps and increased responsiveness of the triceps surae muscles. Also, there was an increased soleus Hoffmann reflex during heel strike of gait cycle. The flexor withdrawal reflex was heighted for individuals with KOA with a lower threshold of the reflex occurring with increased joint compression, but this reflex was modulated with joint mobilizations.

CONCLUSION

Individuals with KOA have motor deficits associated with decreased neural activation, central nervous system sensitization, decreased quadriceps muscle spindle responsiveness, and increased triceps surae muscle activity.

The Time Course of Quadriceps Strength Recovery After Total Knee Arthroplasty Is Influenced by Body Mass Index, Sex, and Age of Patients: Systematic Review and Meta-Analysis

Introduction

For patients with osteoarthritis who have undergone total knee arthroplasty (TKA), quadriceps strength is a major determinant of general physical function regardless of the parameters adopted for functional assessment. Understanding the time course of quadriceps strength recovery and effectiveness of different rehabilitation protocols is a must. Therefore, the aim of this study was to: (i) determine the magnitude of maximal voluntary strength (MVS) loss and the time course of recovery of the quadriceps muscle following TKA, (ii) identify potential moderators of strength outcomes, and (iii) investigate whether different rehabilitation practices can moderate the strength outcomes following TKA, respectively.

Design

General scientific databases and relevant journals in the field of orthopedics were searched, identifying prospective studies that investigated quadriceps’ MVS pre-to post-surgery.

Results

Seventeen studies with a total of 832 patients (39% males) were included. Results showed that in the early post-operative days, the involved quadriceps’ MVS markedly declined, after which it slowly recovered over time in a linear fashion. Thus, the greatest decline of the MVS was observed 3 days after TKA. When compared to pre-operative values, the MVS was still significantly lower 3 months after TKA and did not fully recover up to 6 months following TKA. Furthermore, a meta-regression analysis identified that the variables, time point of evaluation, patient age, sex, and BMI, significantly moderate the MVS of the quadriceps muscle.

Conclusion

The analyzed literature data showed that the decrease in strength of the involved quadriceps muscles following TKA is considerable and lasts for several months post-surgery. Therefore, we recommend to specifically target the strengthening of knee extensor muscles, preserve motor control, and apply appropriate nutrition to ensure a holistic quadriceps muscle recovery. Since age, sex, and BMI were found to be moderating factors in patients’ recovery, further research should include specific analyses considering these moderators.

Modulation in the Stiffness of Specific Muscles of the Quadriceps in Patients With Knee Osteoarthritis and Their Relationship With Functional Ability

Deficits in the flexibility of the quadriceps are one of the risk factors for developing knee joint disorders. No studies have investigated the changes in the stiffness of the quadriceps muscle among patients with knee osteoarthritis (OA). Therefore, the purpose of this study was to investigate changes in the stiffness of specific-muscle of the quadriceps in patients with knee OA and their relationship with functional ability. Twenty-five patients with knee OA and 25 healthy, asymptomatic subjects were recruited in this study. The stiffness of the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) in all participants was evaluated using MyotonPRO at 60° and 90° flexion of the knee joint. The results of this study showed a greater VL stiffness in patients with knee OA than in healthy subjects at both 60° and 90° of knee flexion (p &lt; 0.05). Significant differences in VL, VM and RF stiffness were obtained at different knee joint angles in individuals with and without knee OA (p &lt; 0.05). In addition, there was a positive correlation between VL stiffness and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores in patients with Knee OA (60° of knee flexion: r = 0.508, p = 0.010; 90° of knee flexion: r = 0.456, p = 0.022). These results indicate that there is an increase in VL stiffness in patients with knee OA compared with healthy, asymptomatic subjects, and the quadriceps stiffness was increased with knee flexion in both healthy subjects and patients with knee OA. VL stiffness is associated with WOMAC scores in patients with knee OA.

Steadiness training improves the quadriceps strength and self-reported outcomes in persistent quadriceps weakness following nine months of anterior cruciate ligament reconstruction and failed conventional physiotherapy

Background Persistent quadriceps weakness may occur after anterior cruciate ligament reconstruction, limiting the strength gain. However, steadiness strengthening might change the inability to gain strength. Hence, we determined whether strength training with force steadiness and visual biofeedback can improve knee quadriceps torque, self-reported pain and knee stability in patients with persistent quadriceps weakness after knee anterior cruciate ligament reconstruction. Methods Twenty-five patients (aged 43.7 ± 12.2 years) with persistent quadriceps weakness following knee anterior cruciate ligament reconstruction and 34-weeks of physiotherapy performed unilateral strength training for both lower limbs. Four-weeks of conventional physiotherapy at week-30 were given, confirming the inability to gain torque. Then, steadiness training (isometric knee extension with visual biofeedback) was given for 7-weeks. Knee quadriceps peak torque, strength improvement, determination of responders to the intervention, coherence of strength gain between limbs, and self-reported outcomes (pain and knee stability) were obtained. Descriptive statistics and data inference using mixed-ANOVA, McNemar test, and χ² test were described. Findings Quadriceps torque in the reconstructed knee improved (98.2 ± 47.2-155.2 ± 78.9 Nm; p = 0.031) for most patients (84%). Nevertheless, the torque was lower than the healthy side maintaining asymmetry (155.2 ± 78.9 vs. 209.5 ± 101.8 Nm; p = 0.026). There was high (20%) and medium coherence (80%) between limbs. Knee stability and pain improved in 72% of the patients (p < 0.001). Interpretations Steadiness training after anterior cruciate ligament reconstruction followed 9 months of surgery and failed conventional physiotherapy, improves the persistent weakness and self-reported outcomes, but gain strength was dissimilar between limbs.

Muscle-Bone Relationship in Temporomandibular Joint Disorders after Partial Discectomy

OBJECTIVES

Temporomandibular joint osteoarthritis (TMJ-OA) causes degenerative changes in TMJ tissues. The inter-tissue crosstalk that exacerbates illness and organic changes in bone secondary to TMJ-OA potentially affects the muscles; therefore, patients with a muscular disease might also suffer from bone disease. However, knowledge gaps exist concerning muscle pathology at the onset of TMJ-OA. In this study, we documented the pathogeneses of the bone and muscle at the onset of TMJ-OA using a mouse model.

METHODS

We performed a partial resection of the TMJ disk to establish a mouse model of TMJ-OA. After the onset of TMJ-OA, we performed various measurements at 8, 12, and 16 weeks post-surgery in the defined groups.

RESULTS

The volume of the mandibular head in the TMJ-OA group was significantly greater than that in the control group. The temporal muscles in the TMJ-OA group were significantly deformed compared with those in the control group; however, between-group comparisons did not reveal significant differences in the mandibular head or temporal muscles after surgery. Therefore, we hypothesized that the degree of mandibular head hypertrophy would alter the temporal muscles. A subsequent analysis of the correlation between the bone and muscle confirmed that the deformity of the temporal muscle increased with increasing hypertrophy of the mandibular head. Temporal and masseter muscle contact was observed in 25% of surgical groups.

CONCLUSIONS

This study demonstrates that TMJ-OA progressed when organic changes occurred in bones and muscles, supporting the symbiotic relationship between bones and muscles.

Gamma Loop Dysfunction as a Possible Neurophysiological Mechanism of Arthrogenic Muscle Inhibition: A Narrative Review of the Literature

Context: Quadriceps activation failure has been observed following various pathological conditions in a knee joint such as knee surgery, pain, effusion in knee, and osteoarthritis also could be aging matter. Those patients are unable to attain maximal quadriceps strength for a long period of time although their quadriceps itself is not damaged. This impairment is termed arthrogenic muscle inhibition (AMI). AMI has been of concern to clinicians because this weakness hinders the rehabilitation process considerably and delays recovery because strengthening protocols for the AMI could be largely ineffective. Clinically, it is important to understand neurophysiological mechanisms of the AMI to treat patients with the impairment. Objectives: This is a narrative review of the literature. The purpose of this review is to understand the following: (1) Why investigations of only peripheral spinal reflexive pathways are not enough for elucidation of the mechanisms of the AMI? (2) What we know about the role of the gamma spindle system in AMI so far? (3) Could a dysfunctional gamma spindle system contribute to AMI lead neural changes in upper central nervous system? and (4) Concerns that a clinician should take into consideration when deciding whether to apply therapeutic interventions for AMI. Data Sources: The databases PubMed, MEDLINE, SPORTDiscus, and CINAHL were searched with the terms arthrogenic muscle inhibition (AMI), reflex inhibition, joint mechanoreceptor, gamma loop, corticospinal pathway, spinal reflex, effusion, and joint injury. The remaining citations were collected from references of similar papers. Conclusions: AMI is a limiting factor in the rehabilitation of joint injury. Motor unit recruitment could be hindered in patients with AMI as a result of a dysfunctional gamma spindle system. Clinicians should understand the mechanism of AMI well in order to establish effective rehabilitation programs for AMI. Indeed, AMI is not caused by a single factor, but rather, multiple neural factors can change over time following the appearance of AMI. Therefore, multiple interventions targeting different neural pathways should be combined to achieve the ideal therapeutic goal for the treatment of AMI.

Time course of the effects of vibration on quadriceps function in individuals with anterior cruciate ligament reconstruction

Quadriceps dysfunction is a common, chronic complication following anterior cruciate ligament reconstruction (ACLR) that contributes to aberrant gait biomechanics and poor joint health. Vibration enhances quadriceps function in individuals with ACLR, but the duration of these effects is unknown. This study evaluated the time course of the effects of whole body vibration (WBV) and local muscle vibration (LMV) on quadriceps function. Twenty-four volunteers with ACLR completed 3 testing sessions during which quadriceps isometric peak torque, rate of torque development, and EMG amplitude were assessed prior to and immediately, 10, 20, 30, 45, and 60 min following a WBV, LMV, or control intervention. WBV and LMV (30 Hz, 2g) were applied during six one-minute bouts. WBV increased peak torque 5-11% relative to baseline and control at all post-intervention time points. LMV increased peak torque 6% relative to baseline at 10 min post-intervention and 4-6% relative to control immediately, 10 min, and 20 min post-intervention. The interventions did not influence EMG amplitudes or rate of torque development. The sustained improvements in quadriceps following vibration, especially WBV, suggest that it could be applied at the beginning of rehabilitation sessions to "prime" the central nervous system, potentially improving the efficacy of ACLR rehabilitative exercise.

Acute effect of tendon vibration applied during isometric contraction at two knee angles on maximal knee extension force production

The aim of the current study was to investigate the effect of a single session of prolonged tendon vibration combined with low submaximal isometric contraction on maximal motor performance. Thirty-two young sedentary adults were assigned into two groups that differed based on the knee angle tested: 90° or 150° (180° = full knee extension). Participants performed two fatigue-inducing exercise protocols: one with three 10 min submaximal (10% of maximal voluntary contraction) knee extensor contractions and patellar tendon vibration (80 Hz) another with submaximal knee extensor contractions only. Before and after each fatigue protocol, maximal voluntary isometric contractions (MVC), voluntary activation level (assessed by the twitch interpolation technique), peak-to-peak amplitude of maximum compound action potentials of vastus medialis and vastus lateralis (assessed by electromyography with the use of electrical nerve stimulation), peak twitch amplitude and peak doublet force were measured. The knee extensor fatigue was significantly (P<0.05) greater in the 90° knee angle group (-20.6% MVC force, P<0.05) than the 150° knee angle group (-8.3% MVC force, P = 0.062). Both peripheral and central alterations could explain the reduction in MVC force at 90° knee angle. However, tendon vibration added to isometric contraction did not exacerbate the reduction in MVC force. These results clearly demonstrate that acute infrapatellar tendon vibration using a commercial apparatus operating at optimal conditions (i.e. contracted and stretched muscle) does not appear to induce knee extensor neuromuscular fatigue in young sedentary subjects.

Impaired Regulation of Submaximal Force after ACL Reconstruction: Role of Muscle Spindles

Ongoing motor deficits are routinely present following anterior cruciate ligament (ACL) reconstruction, including the ability to regulate muscle force. While such deficits are known, it is unclear why this occurs. The goal of the current study was to investigate the potential influence of muscle spindle input on submaximal force regulation and muscle activity at the knee in people following ACL reconstruction. Fourteen participants (8 female) who were 6-24 months post-ACL reconstruction and 15 control participants (8 female) undertook submaximal force matching and force modulation tasks before and after 20 min of vibration applied to the patella tendon. Across all tasks, the ACL reconstruction participants were poorer at force matching (P=0.007). The effect of vibration was not significant in either group for the force matching tasks (P=0.06), although there was a reduction in maximum voluntary contraction post-vibration in the control group (P<0.001). The ACL reconstruction group also showed evidence of greater activation of the medial hamstring muscles in comparison to controls (P=0.04). Individuals who have undergone ACL reconstruction have a diminished ability to accurately match and regulate submaximal muscle force, but this does not appear to be related to impaired muscle spindle input. Neuromuscular retraining programs that involve force regulation tasks may be necessary to optimize rehabilitation after ACL reconstruction.

Stretch reflex changes in ACL-deficient individuals and healthy controls during normal and surprise landings

No studies in ACL-D individuals have examined neuromuscular adaptations during landing from a jump where an unexpected mechanical event changes the pre-programmed course of movement. The purpose of this study was to compare pre- and post-landing muscle activation in ACL-D individuals and uninjured controls during normal and surprise landings. Nineteen ACL-D and 17 uninjured volunteered. Participants performed repeated single leg landings from 30 and 15 cm heights. During 15 cm landings, a single surprise landing was performed where participants unexpectedly fell through a false surface at 15 cm to the solid floor a further 15 cm below. Electromyography (EMG) amplitude from vastus lateralis (VL), lateral hamstrings (LH), and soleus (Sol) was recorded. Pre-landing (-60 to 0 ms), post-landing short latency (31-60 ms), and post-landing medium latency (61-90 ms) periods were examined. Comparisons in EMG amplitudes were made across limbs (ACL-D, ACL intact, and control) in 30 cm landings. Additionally, the ratio of EMG amplitude in surprise:30 cm normal landings was analyzed. Post-landing LH EMG was reduced in the ACL-D compared to control limbs at short latencies (P < 0.05). Post-landing VL EMG was reduced in the ACL-D and ACL intact compared to the control limb at both latencies (P < 0.05). Surprise landings notably increased post-landing EMG in all muscles, across all limbs (P < 0.001). However, the gain in VL EMG was significantly greater in ACL-D and ACL intact limbs (P < 0.05). These changes in neuromuscular control of ACL-D individuals during expected and surprise landings may have important implications for rehabilitation, instability, and the risk of secondary injury.

The effects of knee extensor moment biofeedback on gait biomechanics and quadriceps contractile behavior

Individuals with knee joint pathologies exhibit quadriceps dysfunction that, during walking, manifests as smaller peak knee extensor moment (pKEM) and reduced knee flexion excursion. These changes persist despite muscle strengthening and may alter stance phase knee joint loading considered relevant to osteoarthritis risk. Novel rehabilitation strategies that more directly augment quadriceps mechanical output during functional movements are needed to reduce this risk. As an important first step, we tested the efficacy of real-time biofeedback during walking to prescribe changes of ±20% and ±40% of normal walking pKEM values in 11 uninjured young adults. We simultaneously recorded knee joint kinematics, ground reaction forces, and, via ultrasound, vastus lateralis (VL) fascicle length change behavior. Participants successfully responded to real-time biofeedback and averaged up to 55% larger and 51% smaller than normal pKEM values with concomitant and potentially favorable changes in knee flexion excursion. While the VL muscle-tendon unit (MTU) lengthened, VL fascicles accommodated weight acceptance during walking largely through isometric, or even slight concentric, rather than eccentric action as is commonly presumed. Targeted pKEM biofeedback may be a useful rehabilitative and/or scientific tool to elicit desirable changes in knee joint biomechanics considered relevant to the development of osteoarthritis.

Results of muscle strength and range of motion after total open knee synovectomy

AIM OF THE STUDY

Scar tissue formation after synovectomy limits range of motion and causes muscle atrophy. The functional results for patients who underwent total open knee synovectomy often included questionnaires, and assessment of muscle strength was lacking in the literature. Therefore, we aimed to identify the strength and range of motion outcomes for patients who underwent total open synovectomy and to compare the results with the contralateral limb and healthy individuals.

METHOD

Knee range of motion and muscle strength were assessed in fourteen patients that underwent total (anterior and posterior) open knee synovectomy and were compared with the contralateral limb and with 14 healthy individuals matched by sex, age, height, and weight.

RESULTS

The range of motion of flexion decreased 8.4% compared with the contralateral limb (95% CI - 18.9 to - 4.7, p = 0.002) and 9.9% compared with the control group (95% CI 3.9-14.9, p < 0.01). Knee extension strength decreased by 35% compared with the contralateral limb (95% CI 11.1-77.2, p = 0.01) and 37% compared with the control group (95% CI - 112.4-12.1, p = 0.01).

CONCLUSION

Despite the aggressiveness of the surgical procedure, the patients achieved satisfactory functional results.

Neurostructural correlates of strength decrease following total knee arthroplasty: A systematic review of the literature with meta-analysis

Recent literature suggests that alterations in both neural and structural components of the neuromuscular system are major determinants of knee extensor muscle weakness after total knee arthroplasty (TKA). Therefore, the goal of this study was to investigate the maximal voluntary strength (MVS), voluntary muscle activation (VMA), and the cross-sectional area (CSA) of the muscle, up to 33 months after the TKA.  We searched relevant scientific databases and literature for outcomes of interest, including quadriceps MVS, VMA, and CSA. Ten studies met the inclusion criteria and involved a total of 289 patients. The quality of the studies was evaluated by Methodological Index for Non-Randomized Studies (MINORS). Results showed that quadriceps MVS markedly declines in the early postoperative period, after which it slowly and linearly recovers over time. However, the same phenomenon was not observed for VMA and CSA, which were not significantly altered after the TKA. Furthermore, a meta-regression analysis revealed that the change in VMA accounted for 39% of the relative change in quadriceps strength (R2=0.39; p=0.015) in the early postoperative period. Patients treated with TKA had considerable weakness of the quadriceps muscle, which was detectable up to 3 months after surgery. Although the change in VMA largely explains quadriceps weakness, this change and CSA differences were not significant, suggesting that other neural correlates, such as hamstrings coactivation, might alter quadriceps muscle function. Thus, more attention should be paid to address VMA failure and coactivation of antagonist muscles.  More comprehensive rehabilitation approaches may be required to target the whole neural circuit controlling the motor action.

Best Evidence Rehabilitation for Chronic Pain Part 5: Osteoarthritis

Osteoarthritis (OA) is a leading cause of chronic pain and disability in older adults, which most commonly affects the joints of the knee, hip, and hand. To date, there are no established disease modifying interventions that can halt or reverse OA progression. Therefore, treatment is focused on alleviating pain and maintaining or improving physical and psychological function. Rehabilitation is widely recommended as first-line treatment for OA as, in many cases, it is safer and more effective than the best-established pharmacological interventions. In this article, we describe the presentation of OA pain and give an overview of its peripheral and central mechanisms. We then provide a state-of-the-art review of rehabilitation for OA pain—including self-management programs, exercise, weight loss, cognitive behavioral therapy, adjunct therapies, and the use of aids and devices. Next, we explore several promising directions for clinical practice, including novel education strategies to target unhelpful illness and treatment beliefs, methods to enhance the efficacy of exercise interventions, and innovative, brain-directed treatments. Finally, we discuss potential future research in areas, such as treatment adherence and personalized rehabilitation for OA pain.

The effects of patellar tendon vibration on quadriceps strength in anterior cruciate ligament reconstructed knees

OBJECTIVES

To examine the immediate effects of prolonged patellar tendon vibration on quadriceps strength in anterior cruciate ligament reconstructed (ACLR) knees with bone-patellar tendon-bone (BTB) grafts and non-BTB grafts, and healthy control knees.

DESIGN

Pretest-posttest design.

SETTING

Laboratory.

PARTICIPANTS

Young adult participants were stratified into one of three groups: non-BTB graft (n = 25), BTB graft (n = 26), and controls without ACLR (n = 21).

MAIN OUTCOME MEASURES

Maximum voluntary isometric contraction (MVIC) knee extension torque was measured at baseline and following a 20-min vibration intervention applied locally to the patellar tendon.

RESULTS

Our findings suggest there was no difference in the effects of vibration on knee extension torque between the three groups. Knee extension torque significantly increased (effect size = 0.52 [0.18 to 0.81]) from baseline to post-vibration across all three groups (0.30 ± 0.26 Nm/kg, 21.8 ± 20.0%). Both ACLR groups demonstrated significantly lower knee extension torque compared the control group.

CONCLUSIONS

The vibration intervention had a net excitatory effect on quadriceps strength in all three groups and there were no differences in the magnitude of change between the three groups. Vibration could become a useful tool for enhancing quadriceps strength in ACLR and healthy knees.

Knee osteoarthritis induces atrophy and neuromuscular junction remodeling in the quadriceps and tibialis anterior muscles of rats

Knee osteoarthritis (KOA) is associated with muscle weakness, but it is unclear which structures are involved in the muscle changes. This study assessed morphological alterations and the expression of genes and proteins linked to muscular atrophy and neuromuscular junctions (NMJs) in KOA, induced by anterior cruciate ligament transection (ACLT) in rats. Two groups of rats were assessed: control (without intervention) and KOA (ACLT surgery in the right knee). After 8 weeks, quadriceps, tibialis anterior (TA) and gastrocnemius muscles were analyzed (area of muscle fibers, NMJ, gene and protein expression). KOA group showed atrophy in quadriceps (15.7%) and TA (33%), with an increase in atrogin-1 and muscle RING-finger protein-1 (MuRF-1). KOA group showed quadriceps NMJ remodeling (reduction area and perimeter) and decrease in NMJ diameter in TA muscle. The expression of nicotinic acetylcholine receptor (nAChR) γ-nAChR increased and that of α-nAChR and muscle specific tyrosine kinase (MuSK) declined in the quadriceps, with a decrease in ε-nAChR in TA. MuRF-1 protein expression increased in quadriceps and TA, with no changes in neural cell adhesion molecule (NCAM). In conclusion, ACLT-induced KOA promotes NMJ remodeling and atrophy in quadriceps and TA muscles, associated with inflammatory signs and changes in muscle gene and protein expression.

Comparisons of Neuromuscular Training Versus Quadriceps Training on Gait and WOMAC Index in Patients With Knee Osteoarthritis and Varus Malalignment

Objective

The purpose of this study was to compare the effects of neuromuscular training (NMT) and quadriceps training (QT) on the altered gait patterns and Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index in patients with knee osteoarthritis (OA) and varus malalignment.

Methods

Sixty-six patients with knee pain ≥2 on 100-mm visual analog scale, radiographic knee OA changes ≥2 on Kellgren-Lawrence grading scale, and genu varum were allocated randomly into either the neuromuscular training group or quadriceps training group. Twelve weeks of supervised exercise protocol was given to the participants of both groups, which included 3 sessions per week. Primary outcomes were gait variables and self-reported physical function (WOMAC index).

Results

Of 66 knee OA patients, only 31 (94%) in the NMT group and 28 (84.8%) in the QT group completed the exercise protocol and were included in the analysis. There was a significant improvement in gait velocity (P = .022), stride length (P = .009), and global WOMAC index (P = .011) in the NMT group compared to the QT group. However, the scores of cadence (P = .226), gait cycle (P = .332), and double limb support (P = .054) were not found significant in the NMT group compared with the QT group.

Conclusion

The NMT group showed improvement in some of the gait parameters as well as improvement in pain, stiffness, and functional limitation compared with conventional QT. No additional improvement was found in cadence, gait cycle, and double limb support in patients who received NMT.

Association between naturally occurring spine osteoarthritis in geriatric rats and neurogenic inflammation within neurosegmentally linked skeletal muscle

OBJECTIVE

This study aimed to investigate the association between naturally occurring spinal osteoarthritis (OA) (L3-L5), the expression of substance P (SP) centrally (L4-L5) and the presence of neurogenic inflammation within the neurosegmentally linked quadriceps (L2-L5) in elderly rats versus young controls.

DESIGN

Eight aged (27 ± 3.2 months) and six young (4 ± 0.0 months) male Wistar Kyoto rats were euthanized and submitted to micro-computerized tomography for determination of spine OA. SP expression (% area) at the dorsal horn of the spinal cord as well as the relative expression of SP and protease-activated receptor 2 (PAR2) to alpha-tubulin within quadriceps muscle were determined by immunohistochemistry and Western Blot.

RESULTS

Spine osteoarthritis was confirmed in all aged rats but no young controls. Aged rats expressed significant increase of SP protein expression within the dorsal horn (MD = 0.086; 95% CI [0.026 to 0.145]; p = 0.0094) and quadriceps (MD = 1.209; 95% CI [0.239 to 2.179]; p = 0.0191) and PAR2 (MD = 0.797; 95% CI [0.160 to 1.435]; p = 0.0187) compared to young controls.

CONCLUSION

These observations provide novel insight into the potential role of neurogenic inflammation in the pathophysiology of myofascial pain syndrome in the naturally occurring spinal OA in elderly population.

Electromyographic activity of quadriceps muscle during sit-to-stand in patients with unilateral knee osteoarthritis

Objective

The sit-to-stand (STS) is a simple test to evaluate the functional performance of the quadriceps muscle in patients with knee osteoarthritis (OA). The aim was to evaluate the electromyographic (EMG) activity of the ipsilateral quadriceps during STS task at different seat heights and feet positions in patients with severe unilateral OA. The EMG activity was recorded in a group of eight participants with unilateral OA during the performance of STS task in four conditions: (1) knee-height seat with feet together, (2) knee-height seat with feet askew (feet side by side and heel-to-toe), (3) low-height seat (25% lower than knee-height seat) with feet together, and (4) low-height seat with feet askew.

Results

There was a statistically significant difference among the four conditions in the EMG activity (p =0.004). Particularly, the EMG activity of the quadriceps was significantly higher when participants rose from the low height with their feet askew than when they rose from the knee height with their feet placed together (p =0.004) or askew (p =0.002). These results recommend considering initial feet position and seat height when evaluating the functional activity of the quadriceps in patients with unilateral OA using STS test.

Effect of a physiotherapy rehabilitation program on knee osteoarthritis in patients with different pain intensities

[Purpose] To examine the effect of physiotherapy rehabilitation program on moderate knee osteoarthritis in patients with different pain intensities. [Subjects and Methods] Sixty subjects (37 men and 23 women) with moderate knee osteoarthritis participated in the current study. Randomization software was used to select the participating subjects' numbers from the clinic records. They were classified into three groups according to pain intensity: mild, moderate, and severe pain groups. All groups underwent a standard set of pulsed electromagnetic field, ultrasound, stretching exercises, and strengthening exercises. Pain intensity, knee range of motion, knee function, and isometric quadriceps strength were evaluated using the visual analogue scale, universal goniometer, Western Ontario and McMaster Universities osteoarthritis index, and Jamar hydraulic dynamometer, respectively. The evaluation was performed before and after a 4-week rehabilitation program. [Results] All groups showed significant differences in pain intensity, knee range of motion, isometric quadriceps strength, and knee function. The score change in moderate pain group was significantly greater than those in mild and severe pain groups. [Conclusion] Pain intensity is one of the prominent factors that are responsible for the improvement of knee osteoarthritis. Consequently, pain intensity should be considered during rehabilitation of knee osteoarthritis.

Neuromuscular function of the quadriceps muscle during isometric maximal, submaximal and submaximal fatiguing voluntary contractions in knee osteoarthrosis patients

INTRODUCTION

Knee osteoarthrosis (KOA) is commonly associated with a dysfunction of the quadriceps muscle which contributes to alterations in motor performance. The underlying neuromuscular mechanisms of muscle dysfunction are not fully understood. The main objective of this study was to analyze how KOA affects neuromuscular function of the quadriceps muscle during different contraction intensities.

MATERIALS AND METHODS

The following parameters were assessed in 20 patients and 20 healthy controls: (i) joint position sense, i.e. position control (mean absolute error, MAE) at 30° and 50° of knee flexion, (ii) simple reaction time task performance, (iii) isometric maximal voluntary torque (IMVT) and root mean square of the EMG signal (RMS-EMG), (iv) torque control, i.e. accuracy (MAE), absolute fluctuation (standard deviation, SD), relative fluctuation (coefficient of variation, CV) and periodicity (mean frequency, MNF) of the torque signal at 20%, 40% and 60% IMVT, (v) EMG-torque relationship at 20%, 40% and 60% IMVT and (vi) performance fatigability, i.e. time to task failure (TTF) at 40% IMVT.

RESULTS

Compared to the control group, the KOA group displayed: (i) significantly higher MAE of the angle signal at 30° (99.3%; P = 0.027) and 50° (147.9%; P < 0.001), (ii) no significant differences in reaction time, (iii) significantly lower IMVT (-41.6%; P = 0.001) and tendentially lower RMS-EMG of the rectus femoris (-33.7%; P = 0.054), (iv) tendentially higher MAE of the torque signal at 20% IMVT (65.9%; P = 0.068), significantly lower SD of the torque signal at all three torque levels and greater MNF at 60% IMVT (44.8%; P = 0.018), (v) significantly increased RMS-EMG of the vastus lateralis at 20% (70.8%; P = 0.003) and 40% IMVT (33.3%; P = 0.034), significantly lower RMS-EMG of the biceps femoris at 20% (-63.6%; P = 0.044) and 40% IMVT (-41.3%; P = 0.028) and tendentially lower at 60% IMVT (-24.3%; P = 0.075) and (vi) significantly shorter TTF (-51.1%; P = 0.049).

CONCLUSION

KOA is not only associated with a deterioration of IMVT and neuromuscular activation, but also with an impaired position and torque control at submaximal torque levels, an altered EMG-torque relationship and a higher performance fatigability of the quadriceps muscle. It is recommended that the rehabilitation includes strengthening and fatiguing exercises at maximal and submaximal force levels.

Anterior cruciate ligament reconstruction does not induce further gamma loop abnormalities on the intact side of the quadriceps femoris: A longitudinal study

This study aimed to investigate the effect of surgery on the gamma loop of the quadriceps on the side with an intact knee in patients with anterior cruciate ligament (ACL) injuries. We compared longitudinally the response of alpha motor neurons to vibration stimulation of the quadriceps on the side with an intact knee before and after ACL reconstruction. To evaluate alpha motor neuron response, we measured the maximal knee extension strength and integrated electromyography of the vastus medialis, vastus lateralis, and rectus femoris. After obtaining pre-vibration data from each subject, vibration stimulation was applied to the infrapatellar tendon, and the same measurements were performed immediately after stimulation. The results of this study showed that the response to prolonged vibration stimulation on the intact side of the quadriceps did not differ pre- and post-surgery. As vibration stimuli normally elicit a decrease in alpha motor neuron activity in normal individuals, abnormal responses to prolonged vibration stimulation of the quadriceps on the side with an intact knee might be observed in patients with ACL injuries. The abnormality of the gamma loop of the quadriceps on the side with an intact knee was probably induced by the rupture. Based on these results, we conclude that surgery does not induce further gamma loop abnormalities on the intact side of the quadriceps.

Knee morphometric and alignment measurements with MR imaging in young adults with central cartilage lesions of the patella and trochlea

PURPOSE

The goal of this study was to assess whether common measurements of patellar and trochlear morphology and patellar alignment are associated with central cartilage lesions of the patella and trochlea using magnetic resonance imaging (MRI).

METHODS

The MRI examinations of 58 patients (38 women, 20 men; mean age, 28.59 years [range: 19-35 years]) with central cartilage lesions of the patella and trochlea were retrospectively compared to those obtained in 102 control subjects (57 women, 45 men; mean age, 27.05 years [range: 20-35 years]). Patients had Modified Noyes Classification grade IIA, IIB or III cartilage defects whereas control subjects had normal MRI examination of the knee as determined by two radiologists. Patellar measurements of facet asymmetry, patellar tilt, lateral patellofemoral angle, Insall-Salvati ratio, and patellotrochlear cartilage overlap were performed in patients and control subjects along with trochlear measurements of the trochlear depth and width, and sulcal angle. Multivariate logistic regression adjusted for age and body mass index was used to assess associations.

RESULTS

The ratio of the lengths of the medial to lateral facets of the patella (OR=2.7×10^-3; P<0.001), angle of the median eminence of the patella (OR=1.05; P=0.040), lateral patellofemoral angle (OR=0.91; P=0.048), Insall-Salvati ratio (OR=364.4; P<0.001) and edema in the superolateral aspect of Hoffa's fat pad (OR=6.52; P<0.001) were significantly associated with central cartilage lesions of the patella and trochlea.

CONCLUSION

Central cartilage lesions of the patellofemoral joint are associated with patellar and trochlear morphology, and patellar alignment.

The influence of prolonged vibration on motor unit behavior

INTRODUCTION

The purpose of this study was to determine the effects of vibration (VIB) on motor unit (MU) behavior of the vastus lateralis (VL) muscle during a 40% maximal voluntary contraction (MVC).

METHODS

Eleven healthy (age 21.3 ± 2.6 years) individuals participated in the study. Surface electromyography (EMG) data were recorded from the VL during isometric trapezoidal muscle contractions at 40% MVC. Firing events of single MUs and EMG amplitude were reported for the first, middle, and final seconds of a 12-second steady force segment at 40% MVC. VIB was applied at 55 Hz to the patellar tendon for 15 minutes before and continued throughout the remainder of testing (VIB) or remained off (CON).

RESULTS

There were significant increases in MU firing rates during VIB in comparison to CON and no differences in EMG amplitude between VIB and CON.

CONCLUSION

The VIB-mediated reduction in muscle spindle function altered MU behavior at 40% MVC. Muscle Nerve 55: 500-507, 2017.

Effects of muscle strength asymmetry between left and right on isokinetic strength of the knee and ankle joints depending on athletic performance level

[Purpose] The aim of this study was to collect basic data on the effect of asymmetry on the muscle strength of the left and right knee and ankle joints of soccer players at varying athletic performance levels, to guide the development of improved exercise programs. [Subjects and Methods] Forty-nine soccer players at three athletic performance levels participated: 15 professional, 16 amateur, and 18 college. Knee extensor and flexor strength were measured at 60°/sec and 180°/sec, and ankle plantar flexor and dorsiflexor strength were measured at 30°/sec and at 120°/sec. Variables were analyzed by one-way ANOVA. [Results] College soccer players showed greater muscle strength at 60°/sec and 180°/sec in the knee extension muscles of both the right and the left sides, lower muscle strength at 30°/sec and 120°/sec in the dorsiflexor of the right ankle, and similar levels of asymmetry between left and right. The maximum muscle strength on the same side significantly differed in the right ankle joint, with asymmetry between left and right at 30°/sec and 120°/sec. [Conclusion] These findings suggest that muscle strength asymmetry in the ankle joint may lead to counterbalancing muscle strengthening of the knee joint to maintain the center of body mass.

Identifying yoga-based knee strengthening exercises using the knee adduction moment

BACKGROUND

This study aimed to compare muscle activations, co-contraction indices, and the knee adduction moment between static standing yoga postures to identify appropriate exercises for knee osteoarthritis.

METHODS

Healthy young women (24.4 (5.4) years, 23.1 (3.7) kg/m(2)) participated. Primary outcome variables were electromyographic activations of the vastus lateralis, rectus femoris, vastus medialis, biceps femoris, and semitendinosus; co-contraction between the biceps femoris and rectus femoris, and vastus lateralis and vastus medialis; and knee adduction moments of both legs during six static, standing yoga postures (two squatting postures, two lunging postures, a hamstring stretch, and a single-leg balance posture). A two-factor repeated measures analysis of variance was used to identify differences in muscle amplitudes, co-contractions, and knee adduction moment between postures and legs.

FINDINGS

Quadriceps activations were highest during squat and lunge postures (p≤0.001). Hamstring activations were highest during the hamstring stretch (p≤0.003). Squat and lunge postures produced higher co-contraction indices than other postures (p≤0.011). The wide legged squat (Goddess) and lunge with trunk upright (Warrior) produced the lowest knee adduction moments (p≤0.006), while the single-leg balance posture elicited a higher knee adduction moment than all other postures (p<0.05).

INTERPRETATION

Squatting and lunging postures could improve leg strength while potentially minimizing exposure to high knee adduction moments. Future work should evaluate whether these exercises are useful in people with knee osteoarthritis.

Effects of whole-body vibration training with quadriceps strengthening exercise on functioning and gait parameters in patients with medial compartment knee osteoarthritis: a randomised controlled preliminary study

OBJECTIVE

To compare the effects of whole-body vibration training (WBVT) with quadriceps strengthening exercise (QSE) with QSE alone on functioning and gait parameters in patients with medial compartment knee osteoarthritis.

DESIGN

Randomised controlled preliminary study.

SETTING

Department of Rehabilitation Medicine, West China Hospital, Chengdu, Sichuan, People's Republic of China.

SUBJECTS

Thirty-nine patients with medial compartment knee osteoarthritis.

INTERVENTIONS

Participants were assigned at random to one of two groups.

MAIN MEASURES

Visual analogue scale (VAS) for pain, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), timed up and go test (TUG), 6-minute walk distance test (6MWD), and three-dimensional gait analysis during level walking at baseline, 12 weeks and 16 weeks (follow-up).

RESULTS

Compared with baseline, significant improvements in VAS, all WOMAC scales, TUG, 6MWD and all spatiotemporal parameters were seen in both the WBVT+QSE group and the QSE alone group at 12 and 16 weeks. However, the WBVT+QSE group showed greater improvements than the QSE alone group in WOMAC scales (physical function), TUG, 6MWD and cadence at 12 weeks. No differences were found between the WBVT+QSE and QSE alone groups in VAS, WOMAC scales (pain, stiffness), kinematic and kinetic gait parameters, and other spatiotemporal parameters at 12 weeks and 16 weeks.

CONCLUSION

Over a 3-month period, WBVT in combination with QSE improved symptoms, physical function and spatiotemporal parameters in patients with medial compartment knee osteoarthritis, and led to greater improvement than QSE alone in WOMAC scales (physical function), TUG, 6MWD and cadence.

Association between the severity of femoral condylar cartilage erosion related to knee osteoarthritis by ultrasonographic evaluation and the clinical symptoms and functions

OBJECTIVE

To determine the association between the severity of femoral condylar cartilage erosion resulting from knee osteoarthritis (OA) by an ultrasonographic grading system and the clinical symptoms and functions.

DESIGN

Cross-sectional study.

SETTING

A tertiary center.

PARTICIPANTS

Participants (N=101) with and without subjective complaints of knee discomfort were consecutively enrolled. Patients who had ever received knee arthroplasty, who had inflammatory arthritis, and whose knee flexion range of motion was <90° were excluded. A total of 194 knees were evaluated.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

A semiquantitative ultrasonographic grading system was used to evaluate the severity of femoral condylar cartilage erosion. The clinical symptoms and functions were evaluated with the visual analog scale (VAS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Lequesne index. The association of the VAS/WOMAC/Lequesne index with the ultrasonographic grading was assessed.

RESULTS

Positive linear associations were found between the ultrasonographic grading and the following: the VAS and the total scores and pain subscales of both the Lequesne index and WOMAC. Multivariate logistic regression analysis revealed grade-dependent association between VAS and ultrasonographic grading after adjusting for age, sex, and body mass index. The WOMAC and Lequesne index scores were associated with the ultrasonographic grading in more severe degrees, particularly in the pain subscales.

CONCLUSIONS

This semiquantitative ultrasonographic grading system may well reflect the clinical symptoms and functions related to knee OA as evaluated by the VAS, WOMAC, and Lequesne index. This method provides a more comprehensive description and measurement of knee OA.

Knee osteoarthritis: Clinical connections to articular cartilage structure and function

Articular cartilage is a unique biphasic material that supports a lifetime of compressive and shear forces across joints. When articular cartilage deteriorates, whether due to injury, wear and tear or normal aging, osteoarthritis and resultant pain can ensue. Understanding the basic science of the structure and biomechanics of articular cartilage can help clinicians guide their patients to appropriate activity and loading choices. The purpose of this article is to examine how articular cartilage structure and mechanics, may interact with risk factors to contribute to OA and how this interaction provides guidelines for intervention choices This paper will review the microstructure of articular cartilage, its mechanical properties and link this information to clinical decision making.