Patellar Tendon Reflex and Vastus Medialis Hoffmann Reflex Are Down Regulated and Correlated in Women With Patellofemoral Pain

Transcranial magnetic stimulation and electrical stimulation techniques used to measure the excitability of distinct neuronal populations that influence motor output in people with persistent musculoskeletal conditions: A scoping review and narrative synthesis of evidence

Functional impairments are evident in persistent musculoskeletal (MSK) conditions, and linked to altered excitability of neuronal elements contributing to motor output. In MSK conditions, transcranial magnetic stimulation (TMS) or electrical stimulation (ES) techniques have been used to investigate intracortical, corticospinal, spinal and neuromuscular excitability, which influence the efficacy of descending volley transmission to produce movement. This review compiled studies using TMS or ES to investigate neuronal excitability in persistent MSK conditions, to identify techniques used, and to synthesis evidence for neural deficits. We used narrative synthesis to summarise individual study findings. We included 60 studies; 52/60 used at least one TMS technique, and more frequently measured corticospinal tract excitability (48/52). 15/60 studies used at least one ES technique, and more frequently measured neuromuscular excitability (15/15). In tendinopathy, excitability was assessed for a range of distinct neurones; no study measured neuromuscular excitability in low back pain, osteoarthritis or shoulder pain, nor spinal or intracortical excitability in shoulder pain. This review identified a range of TMS and ES techniques used to assess excitability of neural elements. It provides insight for specific deficits contributing to functional impairments in certain persistent MSK conditions, while highlighting evidence gaps hindering the ability to draw meaningful inferences.

Comparison of gluteal muscle central activation in individuals with and without patellofemoral pain

Patellofemoral pain (PFP) is often linked to knee valgus during weight-bearing activities, commonly attributed to gluteal muscle weakness. However, recent research suggests that central nervous system adaptations may also influence muscle function and movement patterns in individuals with PFP. This study compared the central activation ratio (CAR) of the gluteus medius and gluteus maximus between individuals with and without PFP, and assessed the associations between gluteal CAR, frontal plane projection angle of the trunk and lower extremity, and knee function. Twelve individuals without PFP and 10 individuals with PFP participated. We tested CAR of the gluteal muscles with a superimposed burst protocol during a maximum voluntary isometric contraction and evaluated frontal plane kinematics of the trunk and lower extremities during five single leg tasks. Participants with PFP also completed the Anterior Knee Pain Scale (AKPS). Independent t-tests compared CAR between groups, and Pearson correlation coefficients evaluated the associations between CAR, frontal plane kinematics, and AKPS. Individuals with PFP tended to have lower gluteus maximus CAR, though the difference was not statistically significant (PFP: 90.8% ± 7.0%, Control: 94.4% ± 3.0%; p = 0.067). CAR of both the gluteus maximus (R = 0.790, p = 0.003) and gluteus medius (R = 0.584, p = 0.038) were significantly correlated with AKPS scores, and gluteus maximus CAR was associated with trunk lean angle during single leg landing (R = 0.533, p = 0.006). Our data suggest that higher gluteal CAR is associated with better function in individuals with PFP. Lower gluteus maximus CAR contributes to ipsilateral trunk lean during single leg landing, potentially to reduce external hip moments and muscle demand.

Assessing neuromuscular system via patellar tendon reflex analysis using EMG in healthy individuals

Patellar tendon reflex tests are essential for evaluating neuromuscular function and identifying abnormalities in nerve conduction and muscle response. This study explored how age, height, weight, and gender influence reflex response times in healthy individuals, providing a reference for future research on different neuromuscular conditions. We analyzed reflex onset, endpoint, and total duration of reflexes using electromyography (EMG) recordings from 40 healthy participants. Reflexes were elicited by striking the patellar tendon, and participants were grouped based on age, height, weight, and gender. We investigated both the individual and combined effects of these factors on reflex response times. Additionally, height and weight-normalized data were analyzed to clarify their roles in influencing reflexes across age groups. Gender-specific analyses were conducted as well to assess potential differences between males and females. Our findings indicated that reflex onset was significantly delayed in elderly individuals, particularly in taller and heavier individuals, and in males compared to females. Even with height normalization, elderly participants showed slower reflexes. Weight-normalized data revealed that younger participants exhibited longer total reflex durations, likely due to their greater height, which impacted nerve conduction time. This trend was consistent across genders, with males generally exhibiting longer duration of reflex response times. These findings provide insights into how different demographic factors, particularly aging, affect neuromuscular reflexes and could serve as a reference for diagnosing and monitoring neuromuscular disorders.

Physical Activity Variability in Patellofemoral Pain: Relationships With Clinical and Psychological Outcomes

OBJECTIVES

To (1) compare physical activity variability between individuals with patellofemoral pain (PFP) and pain-free individuals and (2) evaluate the relationships of physical activity variability with pain severity, symptom duration, disability, and pain catastrophizing in PFP cohorts.

DESIGN

Cross-sectional case-control study.

SETTING

University research laboratory.

PARTICIPANTS

Individuals with PFP (N=34) and pain-free individuals (N=34) aged 18 to 40 years.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

We assessed physical activity (daily steps and moderate-to-vigorous physical activity [MVPA]) over a period of 14 consecutive days using a triaxial accelerometer. Variability (coefficient of variation) for daily steps and MVPA was calculated, where higher coefficient of variation values indicate greater physical activity variability. We evaluated pain severity (numeric pain rating scale), symptom duration (months), disability (Knee Injury and Osteoarthritis Outcome Score-Patellofemoral subscale), and pain catastrophizing (Pain Catastrophizing Scale). Independent t tests or Mann-Whitney U tests evaluated group differences in physical activity variability. Spearman ρ correlation coefficients were calculated to determine the relationships of physical activity variability with pain severity, symptom duration, disability, and pain catastrophizing in PFP cohorts. Correlation coefficients were interpreted as weak (<0.40), moderate (0.40-0.70), and strong (>0.70).

RESULTS

Age, height, and mass did not differ between individuals with PFP and pain-free individuals (P>.05). Individuals with PFP displayed greater variability in daily steps (P<.001) and MVPA (P=.001) compared to pain-free individuals. In individuals with PFP, greater variability in daily steps was moderately related to higher pain severity (ρ=0.41, P=.016), while greater variability in MVPA was weakly related to higher pain severity (ρ=0.36, P=.037).

CONCLUSIONS

Individuals with PFP demonstrated greater variability in physical activity compared to pain-free individuals, which positively related to more severe pain. Future PFP research should explore the underlying factors contributing to increased physical activity variability and their potential implications for pain management.

Brain and Spinal Cord Adaptations Associated With Patellofemoral Pain: A Systematic Review and Meta-Analysis

Objective

To evaluate the evidence for altered cortical and spinal cord functions in individuals with patellofemoral pain (PFP).

Methods

We conducted a comprehensive search of databases to appraise and analyze the studies published prior to December 10, 2021 that examined spinal reflex excitability measured using Hoffmann reflex (H-reflex) amplitudes, corticospinal excitability measured using transcranial magnetic stimulation (TMS)-elicited motor evoked potential (MEP) amplitudes, motor threshold (MT), or stimulus-response (SR) curves, cortical reorganization assessed using TMS cortical mapping or structural magnetic resonance imaging (MRI), or functional changes of the brain assessed using functional MRI (fMRI) in individuals with PFP.

Results

Eight studies were eligible for analyses. While an earlier study showed that pain had no effect on the H-reflex amplitude of the quadriceps muscle, more recent evidence reported a decrease in vastus medialis (VM) H-reflex amplitude in participants with PFP. VM H-reflex amplitude was correlated with pain, chronicity, physical function, and isometric knee extensor torque production in participants with PFP. Altered corticospinal excitability was reported in participants with PFP, observed as increased MT in the VM and vastus lateralis (VL) muscles. In addition, cortical reorganization has been observed, where decreased number of cortical peaks, shifts and reduced volumes, and increased overlap of motor cortex representations for the VM, VL, and rectus femoris (RF) muscles were reported in participants with PFP.

Conclusion

There is emerging evidence on altered cortical and spinal cord functions in individuals with PFP, however, solid conclusions cannot be drawn due to limited literature available. Further research is needed to better understand the adaptations of the brain and spinal cord in this population.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier: CRD42020212128.

Arthrogenic Muscle Inhibition: Best Evidence, Mechanisms, and Theory for Treating the Unseen in Clinical Rehabilitation

CONTEXT

Arthrogenic muscle inhibition (AMI) impedes the recovery of muscle function following joint injury, and in a broader sense, acts as a limiting factor in rehabilitation if left untreated. Despite a call to treat the underlying pathophysiology of muscle dysfunction more than three decades ago, the continued widespread observations of post-traumatic muscular impairments are concerning, and suggest that interventions for AMI are not being successfully integrated into clinical practice.

OBJECTIVES

To highlight the clinical relevance of AMI, provide updated evidence for the use of clinically accessible therapeutic adjuncts to treat AMI, and discuss the known or theoretical mechanisms for these interventions.

EVIDENCE ACQUISITION

PubMed and Web of Science electronic databases were searched for articles that investigated the effectiveness or efficacy of interventions to treat outcomes relevant to AMI.

EVIDENCE SYNTHESIS

122 articles that investigated an intervention used to treat AMI among individuals with pathology or simulated pathology were retrieved from 1986 to 2021. Additional articles among uninjured individuals were considered when discussing mechanisms of effect.

CONCLUSION

AMI contributes to the characteristic muscular impairments observed in patients recovering from joint injuries. If left unresolved, AMI impedes short-term recovery and threatens patients' long-term joint health and well-being. Growing evidence supports the use of neuromodulatory strategies to facilitate muscle recovery over the course of rehabilitation. Interventions should be individualized to meet the needs of the patient through shared clinician-patient decision-making. At a minimum, we propose to keep the treatment approach simple by attempting to resolve inflammation, pain, and effusion early following injury.

Local neuromuscular characteristics associated with patellofemoral pain: A systematic review and meta-analysis

BACKGROUND

Local neuromuscular deficits have been reported in people with patellofemoral pain. We synthesised the neuromuscular characteristics associated with patellofemoral pain to help identify interventional targets and potential mechanisms.

METHODS

Five databases were searched for local neuromuscular characteristics in case-control studies. Electromyography, flexibility, muscle performance and cross-sectional area data were derived from functional or isolated task investigations and synthesised accordingly. An evidence gap map was constructed.

FINDINGS

Sixty-seven studies were included. In functional tasks, electromyographic investigations showed moderate evidence of small effect for vastus medialis onset-delays relative to vastus lateralis (0.44 [0.03, 0.85]) during stepping/stair negotiation tasks, and higher biceps femoris mean excitation amplitudes (0.55 [0.06, 1.04]) in single-leg triple-hop test. In isolated tasks, we found moderate evidence of medium effect for lower Hoffman-reflex amplitude of vastus medialis (-1.12 [-1.56, -0.67]). Muscle performance investigations showed; strong evidence with medium and small effects for lower extensors concentric (-0.61 [-0.81, -0.40]) and eccentric (-0.56 [-0.79, -0.33]) strength, and moderate evidence of medium effect of lower isometric (-0.64 [-0.87, -0.41]) strength, moderate evidence with small effect for rate of force development to 30% (-0.55[-0.89, -0.21]), 60% (-0.57[-0.90, -0.25]) and medium effect to 90% (-0.76[-1.43, -0.10]) of maximum voluntary contraction, and small effect for lower flexors concentric strength (-0.46 [-0.74, -0.19]) and extensors total work (-0.48 [-0.90, -0.07]). Flexibility investigations showed tighter hamstrings (-0.57 [-0.99, -0.14]).

INTERPRETATION

Differences within quadriceps and hamstrings motor-control, hamstrings tightness, and quadriceps and hamstrings weakness are associated with patellofemoral pain, and can be used to guide investigations of treatment effects.

Impaired Isometric, Concentric, and Eccentric Rate of Torque Development at the Hip and Knee in Patellofemoral Pain

ABSTRACT

Ferreira, AS, de Oliveira Silva, D, Barton, CJ, Briani, RV, Taborda, B, Pazzinatto, MF, and de Azevedo, FM. Impaired isometric, concentric, and eccentric rate of torque development at the hip and knee in patellofemoral pain. J Strength Cond Res 35(9): 2492-2497, 2021-The aims of this study were to compare maximal muscle strength and rate of torque development (RTD) of knee extensor and hip abductor during isometric, concentric, and eccentric contractions between women with and without patellofemoral pain (PFP). Thirty-eight women with PFP (PFPG) and 38 pain-free women (CG) participated in this study. Isometric, concentric, and eccentric maximal torque and RTD of knee extensor and hip abductor were assessed using an isokinetic dynamometer. Rate of torque development was calculated as the change in torque over the change in time from torque onset to 30, 60, and 90% of the maximal torque (RTD30%, RTD60%, and RTD90%) during isometric, concentric, and eccentric contractions. PFPG had lower isometric, concentric, and eccentric knee extensor maximal torque (29.9, 28.3, and 26.7%) compared with the CG. For knee extensor RTD, PFPG had slower isometric RTD30% (17.8%), RTD60% (21.5%), and RTD90% (23.4%); slower concentric RTD30% (35.7%), RTD60% (29.3%), and RTD90% (28.2%); and slower eccentric RTD30% (20.5%), RTD60% (25.2%), and RTD90% (22.5%) compared with the CG. PFPG had lower isometric, concentric, and eccentric hip abductor maximal torque (28.3, 21.8, and 17%) compared with the CG. For hip abductor RTD, PFPG had slower isometric RTD30% (32.6%), RTD60% (31.1%), and RTD90% (25.4%); slower concentric RTD90% (11.5%); and slower eccentric RTD30% (19.8%), RTD60% (26.4%), and RTD90% (24%) compared with the CG. In conclusion, women with PFP presented deficits in both maximal strength and RTD of knee extensor and hip abductor during isometric, concentric, and eccentric contractions, which highlight the potential importance of addressing different aspects of muscle function through exercise therapy.

Neurophysiological changes of brain and spinal cord in individuals with patellofemoral pain: a systematic review and meta-analysis protocol

INTRODUCTION

Reduced neuromuscular control due to altered neurophysiological functions of the central nervous system has been suggested to cause movement deficits in individuals with patellofemoral pain (PFP). However, the underlying neurophysiological measures of brain and spinal cord in this population remain to be poorly understood. The purpose of this systematic review is to evaluate the evidence for altered cortical and spinal cord functions in individuals with PFP.

METHODS AND ANALYSIS

The protocol for conducting the review was prepared using the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols guidelines. We will systematically search the literature that examines cortical and spinal cord functions in individuals with PFP, aged 18-45 years. The studies for cross-sectional, prospective, longitudinal, case-control and randomised control trial designs will be included from the following databases: PubMed (MEDLINE), EMBASE and Web of Science. Only studies published in English prior to 1 February 2021 will be included. The risk of bias and quality assessment will be performed using National Institutes of Health's Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. We will conduct meta-analysis of the data where appropriate. Narrative synthesis will be taken if a meta-analysis is not possible.

ETHICS AND DISSEMINATION

This is a systematic review from the existing literature and does not require ethical approval. The results of this study will be published in a peer-reviewed journal in the field of rehabilitation medicine, sports/orthopaedic medicine or neurology, regardless of the outcome.

PROSPERO REGISTRATION NUMBER

CRD42020212128.

The effect of experimental and clinical musculoskeletal pain on spinal and supraspinal projections to motoneurons and motor unit properties in humans: A systematic review

BACKGROUND AND OBJECTIVE

Numerous studies have examined the influence of pain on spinal reflex excitability, motor unit behaviour and corticospinal excitability. Nevertheless, there are inconsistencies in the conclusions made. This systematic review sought to understand the effect of pain on spinal and supraspinal projections to motoneurons and motor unit properties by examining the influence of clinical or experimental pain on the following three domains: H-reflex, corticospinal excitability and motor unit properties.

DATABASES AND DATA TREATMENT

MeSH terms and preselected keywords relating to the H-reflex, motor evoked potentials and motor unit decomposition in chronic and experimental pain were used to perform a systematic literature search using Cumulative Index of Nursing and Allied Health Literature (CINAHL), Excerpta Medica dataBASE (EMBASE), Web of Science, Medline, Google Scholar and Scopus databases. Two independent reviewers screened papers for inclusion and assessed the methodological quality using a modified Downs and Black risk of bias tool; a narrative synthesis and three meta-analyses were performed.

RESULTS

Sixty-one studies were included, and 17 different outcome variables were assessed across the three domains. Both experimental and clinical pain have no major influence on measures of the H-reflex, whereas experimental and clinical pain appeared to have differing effects on corticospinal excitability. Experimental pain consistently reduced motor unit discharge rate, a finding which was not consistent with data obtained from patients. The results indicate that when in tonic pain, induced via experimental pain models, inhibitory effects on motoneuron behaviour were evident. However, in chronic clinical pain populations, more varied responses were evident likely reflecting individual adaptations to chronic symptoms.

SIGNIFICANCE

This is a comprehensive systematic review and meta-analysis which synthesizes evidence on the influence of pain on spinal and supraspinal projections to motoneurons and motor unit properties considering measures of the H-reflex, corticospinal excitability and motor unit behaviour. The H-reflex is largely not influenced by the presence of either clinical or experimental pain. Whilst inhibitory effects on corticospinal excitability and motor unit behaviour were evident under experimental pain conditions, more variable responses were observed for people with painful musculoskeletal disorders.

A stimulus rate that is not influenced by homosynaptic post-activation depression in chronic stroke

PURPOSE

To determine a stimulus rate that is not influenced by homosynaptic post-activation depression for H-reflex studies in patients with chronic spasticity.

MATERIALS AND METHODS

A cohort of 15 chronic stroke patients with soleus spasticity who received inpatient treatment at our rehabilitation centre participated in this study. The effect of stimulus frequency related depression on H-reflex size was tested using four different stimulus rates (0.1, 0.2, 0.3 and 1 Hz). The affected sides stibial nerve was stimulated by a bipolar electrode. The H-reflex was recorded from the affected sideed sidee sidehe affected smine stimulus frequency related depression of H-reflex size, amplitude of the first H-reflex response (H₁) was used as control and amplitude of the second H-reflex response (H₂) as test.

RESULTS

H₂ amplitude for frequency of 1 Hz, 0.3 Hz, 0.2 Hz and 0.1 Hz were 74.3, 84.1, 85.5 and 92.7% of H₁, respectively. Depression of H₂ amplitude was statistically significant for 1 Hz, 0.3 Hz and 0.2 Hz (p < 0.001, p = 0.002, p = 0.024, respectively).

CONCLUSIONS

Higher frequency stimulation of Ia afferents than 0.1 Hz induced a stimulus frequency-related depression of H-reflex size in patients with chronic spasticity. The optimal stimulus rate for H-reflex was found to be 0.1 Hz.

Isometric exercises and somatosensory training as intervention programmes for patellofemoral pain in young dancers

Patellofemoral pain (PPF) is a common problem experienced by young dancers. Currently, there is no clear indication as to the optimal intervention programme for reducing the level of pain and improving functional abilities in young dancers with PFP. Our aim was to examine the efficacy of two intervention programmes compared with controls in relation to PFP symptoms (shown by pain level, Grinding test, and patellar inhibition test-PIT) and functional abilities of dancers with PFP. Ninety-eight young dancers (mean age 13.4 ± .97) with PFP were assessed for clinical parameters and functional abilities pre and post an intervention programme lasting 12 weeks. Using cluster sampling controlling for grade and school, the dancers were divided into three groups: isometric exercises (IE), somatosensory training (ST), and control (CO). Post-intervention, significantly lower pain levels upon patellar provocation testing were reported for the two treatment groups compared with controls. There was a significantly lower rate of legs recovered in the CO group compared with both intervention groups on the Grinding test, and on the PIT. Postural balance ability and proprioception abilities were significantly better post-treatment for the two treatment groups compared with controls. A significant interaction showed that hip abduction muscle strength improved more in the IE group. In conclusion, both isometric exercises and somatosensory training were effective for decreasing clinical symptoms and improving some functional abilities in young dancers with PFP. Further studies on these types of interventions could determine the most effective training protocol for prevention and treatment of PFP in young dancers.