Arthrogenic muscle response induced by an experimental knee joint effusion is mediated by pre- and post-synaptic spinal mechanisms

Abnormality in re-programing of preparatory muscle activity for landing following unpredictable events in patients with anterior cruciate ligament injury

BACKGROUND

Anterior cruciate ligament deficiency (ACL-D) causes dysfunction in the quadriceps femoris muscle, and this dysfunction hampers a safe return to sports. However, how the dysfunctional quadriceps femoris muscle affects instantaneous re-programming of motor command in response to unpredictable events remains unknown. This study aimed to examine the effects of ACL-D on re-programming of preparatory muscle activity during an unpredictable landing task.

METHODS

Eighteen patients with ACL-D and 20 healthy participants (controls) performed normal landing and surprise landing tasks. In the surprise landing task, a false floor, designed to dislodge easily under load, was positioned in the middle of the descent path. This setup causes participants to unpredictably fall through the false floor onto the actual landing surface. Electromyography data collected during the period after passing through the false floor until landing was segmented into two equal halves. The average electromyography amplitude for each muscle in each period was compared between patients and controls.

RESULTS

In the vastus medialis and rectus femoris during the surprise landing task, the average electromyography amplitude during only the second half period in patients with ACL-D was significantly smaller than that in controls (p = 0.011 and 0.004, respectively).

CONCLUSIONS

Abnormalities were detected in the re-programming of preparatory muscle activation during an unpredictable landing task in the vastus medialis and rectus femoris of patients with ACL-D. The surprise landing task used in the present study has the potential to become a diagnostic tool to evaluate readiness for safely returning to sports.

Sensorimotor Dysfunction Following Anterior Cruciate Ligament Reconstruction- an Afferent Perspective: A Scoping Review

Background

Sensorimotor dysfunction is thought to occur following anterior cruciate ligament (ACL) injury which may have implications on future reinjury risk. Dysfunction has been demonstrated within the efferent component of the sensorimotor system. However, no reviews have examined the two main components of the afferent system: the visual and somatosensory systems.

Hypothesis/Purpose

This study aimed to report differences in function (central processing and local processing) within the (1) somatosensory and (2) visual systems between individuals following anterior cruciate ligament reconstruction (ACLR) and healthy controls (between-subject). The study also aimed to report differences in function within the two systems between the two limbs of an individual following ACLR (within-subject).

Study Design

Scoping review.

Methods

A search was conducted in PubMed, SPORTDiscus, CINAHL, Medline and Embase up until September 2021. Level I-IV studies assessing somatosensory and visual systems were included if they compared ACLR limbs to the uninjured contralateral limb (within-subject) or a healthy control limb (between-group). The function of somatosensory and visual systems was assessed across both central processing (processing of information in the central cortex) and local processing (all other assessments outside of central processing of information).

Results

Seventy studies were identified (52 somatosensory, 18 visual). Studies examining somatosensory central processing demonstrated significant differences; 66% of studies exhibited within-subject differences and 100% of the studies exhibited between-group differences. Studies examining local somatosensory processing had mixed findings; 40% of the 'joint position sense (JPS)' and 'threshold to detect motion (TTDM)' studies showed significant within-subject differences (JPS=0.8°-3.8° and TTDPM=0.2°-1.4°) and 42% demonstrated significant between-group differences (JPS=0.4°-5° and TTDPM=0.3°-2.8°). Eighty-three percent of visual central processing studies demonstrated significant dysfunction between-groups with no studies assessing within-subject differences. Fifty percent of the studies examining local visual processing demonstrated a significant between-group difference.

Conclusion

Significant differences in central processing exist within somatosensory and visual systems following ACLR. There is mixed evidence regarding local somatosensory and visual processing. Increased compensation by the visual system and local visual processing dysfunction may occur in conjunction with somatosensory dysfunction.

Incidence of and Risk Factors for Arthrogenic Muscle Inhibition in Acute Anterior Cruciate Ligament Injuries: A Cross-Sectional Study and Analysis of Associated Factors From the SANTI Study Group

BACKGROUND

Arthrogenic muscle inhibition (AMI) is a process in which neural inhibition after injury or surgery to the knee results in quadriceps activation failure and knee extension deficit.

PURPOSE

To determine the incidence and spectrum of the severity of AMI after acute anterior cruciate ligament (ACL) injury using the Sonnery-Cottet classification, to determine the interobserver reliability of the classification system, and to investigate potential important factors associated with AMI after ACL injury.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Consecutive patients who had an acute ACL injury between October 2021 and February 2022 were considered for study inclusion. Eligible patients underwent a standardized physical examination at their first outpatient appointment. This included an assessment of quadriceps inhibition, identification of any extension deficits, and grading of AMI and its reversibility according to the Sonnery-Cottet classification.

RESULTS

A total of 300 consecutive patients with acute ACL ruptures were prospectively enrolled in the study. Of them, 170 patients (56.7%) had AMI. Patients evaluated with AMI showed a significantly inferior Lysholm score, International Knee Documentation Committee score, Simple Knee Value, and Knee injury and Osteoarthritis Outcome Score than patients without AMI (P < .0001). Multivariate analysis revealed that the presence of effusion, concomitant injuries, and high pain scores were associated with a significantly greater risk of AMI. Additional associations with the presence of AMI included a short duration between injury and evaluation, the use of crutches, and using a pillow as a support at night. In contrast, a previous ACL injury was associated with significantly lower odds of developing AMI (OR, 0.025; 95% CI, 0-0.2; P = .014). Among the 170 patients with AMI, 135 patients (79%) showed a resolution of their inhibition at the end of the consultation after application of simple exercises; the remaining 35 patients required specific rehabilitation. Interobserver reliability of the classification system was almost perfect (95% CI, 0.86-0.99).

CONCLUSION

AMI occurs in over half of patients with acute ACL injuries. When it occurs, it is easily reversible in the majority of patients with simple exercises targeted at abolishing AMI. The presence of "red flags" should increase the index of suspicion for the presence of AMI, and these include the presence of an effusion, high pain scores, a short time between injury and evaluation, multiligament injuries, the use of crutches, and using a pillow as a support at night. Patients with a history of ipsilateral or contralateral ACL injury are at a significantly lower risk of AMI than those with a first-time ACL injury.

Anterior Cruciate Ligament Injury Prevention and Rehabilitation

At all levels of American football, knee injuries are common, with injuries to the anterior cruciate ligament (ACL) making up a significant proportion. Historically, ACL injuries were career-altering for professional players, but innovative techniques in surgery and rehabilitation have returned many to the field. While there is a consensus on surgical techniques for ACL reconstruction, significant discrepancies remain on injury prevention and rehabilitation programs. This review article describes the burden of ACL injury on players in the National Football League, best practices in injury prevention and rehabilitation, and evidence-based recommendations for preparing injured athletes to return to play.

Quadriceps Weakness is Associated with Neuroplastic Changes Within Specific Corticospinal Pathways and Brain Areas After Anterior Cruciate Ligament Reconstruction: Theoretical Utility of Motor Imagery-Based Brain-Computer Interface Technology for Rehabilitation

Persistent quadriceps weakness is a problematic sequela of anterior cruciate ligament reconstruction (ACLR). The purposes of this review are to summarize neuroplastic changes after ACL reconstruction; provide an overview of a promising interventions, motor imagery (MI), and its utility in muscle activation; and propose a framework using a brain-computer interface (BCI) to augment quadriceps activation. A literature review of neuroplastic changes, MI training, and BCI-MI technology in postoperative neuromuscular rehabilitation was conducted in PubMed, Embase, and Scopus. Combinations of the following search terms were used to identify articles: "quadriceps muscle," "neurofeedback," "biofeedback," "muscle activation," "motor learning," "anterior cruciate ligament," and "cortical plasticity." We found that ACLR disrupts sensory input from the quadriceps, which results in reduced sensitivity to electrochemical neuronal signals, an increase in central inhibition of neurons regulating quadriceps control and dampening of reflexive motor activity. MI training consists of visualizing an action, without physically engaging in muscle activity. Imagined motor output during MI training increases the sensitivity and conductivity of corticospinal tracts emerging from the primary motor cortex, which helps "exercise" the connections between the brain and target muscle tissues. Motor rehabilitation studies using BCI-MI technology have demonstrated increased excitability of the motor cortex, corticospinal tract, spinal motor neurons, and disinhibition of inhibitory interneurons. This technology has been validated and successfully applied in the recovery of atrophied neuromuscular pathways in stroke patients but has yet to be investigated in peripheral neuromuscular insults, such as ACL injury and reconstruction. Well-designed clinical studies may assess the impact of BCI on clinical outcomes and recovery time. Quadriceps weakness is associated with neuroplastic changes within specific corticospinal pathways and brain areas. BCI-MI shows strong potential for facilitating recovery of atrophied neuromuscular pathways after ACLR and may offer an innovative, multidisciplinary approach to orthopaedic care.

Level of Evidence

V, expert opinion.

Neuromuscular Consequences of Lumbopelvic Dysfunction: Research and Clinical Perspectives

Injuries involving the lumbopelvic region (ie, lumbar spine, pelvis, hip) are common across the lifespan and include pathologies such as low back pain, femoroacetabular impingement syndrome, labrum tear, and osteoarthritis. Joint injury is known to result in an arthrogenic muscle response which contributes to muscle weakness and altered movement patterns. The purpose of this manuscript is to summarize the arthrogenic muscle response that occurs across lumbopelvic region pathologies, identify methods to quantify muscle function, and propose suggestions for future research. While each lumbopelvic region pathology is unique, there are a few common impairments and a relative consistent arthrogenic muscle response that occurs across the region. Hip muscle weakness and hip joint range of motion limitations occur with both lumbar spine and hip pathologies, and individuals with low back pain are known to demonstrate inhibition of the transversus abdominis and multifidus. Assessment of muscle inhibition is often limited to research laboratory settings, but dynamometers, ultrasound imaging, and electromyography offer clinical capacity to quantify muscle function and inform treatment pathways. Future studies should systematically determine the arthrogenic muscle response across multiple muscle groups and the timeline for changes in muscle function and determine whether disinhibitory modalities improve functional outcomes beyond traditional treatment approaches.

Alterations in Cortical Activation among Soccer Athletes with Chronic Ankle Instability during Drop-Jump Landing: A Preliminary Study

Background: Chronic ankle instability (CAI) is a common peripheral joint injury and there is still no consensus on the mechanisms. It is necessary to investigate electrocortical parameters to provide clinical insight into the functional alterations of brain activity after an ankle sprain, which would greatly affect the implementation of rehabilitation plans. The purpose of this study was to assess cortical activation characteristics during drop-jump landing among soccer athletes with CAI. Methods: A total of 24 participants performed the drop-jump landing task on a force platform while wearing a 64-channel EEG system. The differences of power spectral density (PSD) in theta and alpha (alpha-1 and alpha-2) bands were analyzed between two groups (CAI vs. CON) and between two limbs (injured vs. healthy). Results: CAI participants demonstrated significantly higher theta power at the frontal electrode than that in healthy control individuals (F(1,22) = 7.726, p = 0.011, η2p = 0.260). No difference in parietal alpha-1 and alpha-2 power was found between groups (alpha-1: F(1,22) = 0.297, p = 0.591, η2p = 0.013; alpha-2: F(1,22) = 0.118, p = 0.734, η2p = 0.005). No limb differences were presented for any frequency band in selected cortical areas (alpha-1: F(1,22) = 0.149, p = 0.703, η2p = 0.007; alpha-2: F(1,22) = 0.166, p = 0.688, η2p = 0.007; theta: F(1,22) = 2.256, p = 0.147, η2p = 0.093). Conclusions: Theta power at the frontal cortex was higher in soccer athletes with CAI during drop-jump landing. Differences in cortical activation provided evidence for an altered neural mechanism of postural control among soccer athletes with CAI.

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.

How does anterior cruciate ligament reconstruction affect the functioning of the brain and spinal cord? A systematic review with meta-analysis

OBJECTIVE

To examine the effect of anterior cruciate ligament (ACL) reconstruction on spinal-reflex and corticospinal excitability of the quadriceps muscle.

METHODS

A comprehensive electronic database search was performed to identify studies that objectively measured Hoffmann reflex to muscle response ratio, motor threshold, and motor evoked potentials after ACL reconstruction. Pooled standardized mean differences (SMDs) were computed using a random effects meta-analysis model.

RESULTS

A total of 13 studies were eligible for analysis. The Hoffmann reflex to muscle response ratio was significantly higher on both the reconstructed and non-reconstructed legs when compared with the healthy control leg (SMD = 0.28, 95% confidence interval (95%CI): 0.08-0.49, p = 0.006 and SMD = 0.22, 95%CI: 0.04-0.40, p = 0.016, respectively) but did not differ between legs (SMD = 0.10, 95%CI: -0.01 to 0.21, p = 0.078). The motor threshold was significantly higher on both the reconstructed (SMD = 0.76, 95%CI: 0.40-1.12, p < 0.001) and non-reconstructed legs (SMD = 0.47, 95%CI: 0.00-0.95, p = 0.049) when compared with the legs of healthy controls. The reconstructed leg also had a higher motor threshold when compared with the non-reconstructed leg (SMD = 0.20, 95%CI: 0.06-0.34, p = 0.005). These changes were paralleled by bilateral reductions in quadriceps strength (ACL reconstructed: SMD = -0.78, 95%CI: -1.07 to -0.49, p < 0.001; non-reconstructed: SMD = -0.32, 95%CI: -0.63 to -0.01, p = 0.042) and quadriceps voluntary activation (ACL reconstructed: SMD = -0.73, 95%CI: -0.97 to -0.50, p < 0.001; non-reconstructed: SMD = -0.55, 95%CI: -0.82 to -0.27, p < 0.001) when compared with healthy controls.

CONCLUSION

There is increased excitability of the spinal-reflex pathways and reduced excitability of the corticospinal pathways following ACL reconstruction. These changes are paralleled by reductions in quadriceps strength and voluntary activation, suggesting that rehabilitation interventions should focus on normalizing the excitability of neural pathways to effectively address quadriceps dysfunction after ACL reconstruction.

Neuromuscular Function of the Knee Joint Following Knee Injuries: Does It Ever Get Back to Normal? A Systematic Review with Meta-Analyses

BACKGROUND

Neuromuscular deficits are common following knee injuries and may contribute to early-onset post-traumatic osteoarthritis, likely mediated through quadriceps dysfunction.

OBJECTIVE

To identify how peri-articular neuromuscular function changes over time after knee injury and surgery.

DESIGN

Systematic review with meta-analyses.

DATA SOURCES

PubMed, Web of Science, Embase, Scopus, CENTRAL (Trials).

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Moderate and high-quality studies comparing neuromuscular function of muscles crossing the knee joint between a knee-injured population (ligamentous, meniscal, osteochondral lesions) and healthy controls. Outcomes included normalized isokinetic strength, muscle size, voluntary activation, cortical and spinal-reflex excitability, and other torque related outcomes.

RESULTS

A total of 46 studies of anterior cruciate ligament (ACL) and five of meniscal injury were included. For ACL injury, strength and voluntary activation deficits were evident (moderate to strong evidence). Cortical excitability was not affected at < 6 months (moderate evidence) but decreased at 24+ months (moderate evidence). Spinal-reflex excitability did not change at < 6 months (moderate evidence) but increased at 24+ months (strong evidence). We also found deficits in torque variability, rate of torque development, and electromechanical delay (very limited to moderate evidence). For meniscus injury, strength deficits were evident only in the short-term. No studies reported gastrocnemius, soleus or popliteus muscle outcomes for either injury. No studies were found for other ligamentous or chondral injuries.

CONCLUSIONS

Neuromuscular deficits persist for years post-injury/surgery, though the majority of evidence is from ACL injured populations. Muscle strength deficits are accompanied by neural alterations and changes in control and timing of muscle force, but more studies are needed to fill the evidence gaps we have identified. Better characterisation and therapeutic strategies addressing these deficits could improve rehabilitation outcomes, and potentially prevent PTOA.

TRIAL REGISTRATION NUMBER

PROSPERO CRD42019141850.

Assessment of Quadriceps Corticomotor and Spinal-Reflexive Excitability in Individuals with a History of Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis

BACKGROUND

Differences in the excitability of motor generating neural pathways are reported following anterior cruciate ligament reconstruction (ACLR) that is associated with quadriceps dysfunction and theorized to prevent the full recovery of muscle function.

OBJECTIVE

The aims of this systematic review and meta-analysis were to compare quadriceps neural excitability between the involved ACLR limb, the uninvolved limb, and uninjured controls, and to determine at what time intervals these differences are present after surgery.

METHODS

We conducted a search of PubMed, SPORTDiscus, Embase, and Web of Science, and extracted measures assessing difference of quadriceps spinal-reflexive, corticospinal, and intracortical excitability from studies that compared (1) involved limb to the uninvolved limb, (2) involved limb to a control limb, or (3) uninvolved limb to a control limb. We stratified time at 24 months, since this represents a period of heightened risk for reinjury. A modified Downs and Black checklist and Egger's test were used to determine the methodological quality of individual studies and risk of bias between studies.

RESULTS

Fourteen studies comprising 611 participants (371 individuals with a history of ACLR; median time from surgery: 31.5 months; range 0.5-221.1 months) were included in the review. Overall, the involved (g = 0.60, 95% CI [0.24, 0.96]) and uninvolved (g = 0.49, 95% CI [0.00, 0.98]) limbs exhibited greater motor threshold (MT) in comparison to uninjured controls. Motor-evoked potential (MEP) amplitudes were greater in the uninvolved limb in comparison to uninjured controls (g = 0.31, 95% CI [0.03, 0.59]). Lesser intracortical inhibition was exhibited in the uninvolved limb compared to uninjured controls (g = 0.54, 95% CI [0.14, 0.93]). When stratified by time from surgery, MEP amplitudes were greater in the uninvolved limb compared to uninjured controls (g = 0.33, 95% CI [0.03, 0.63]) within the first 24 months after surgery. When evaluated more than 24 months after surgery, the involved limb exhibited greater Hoffmann reflex (H-reflex) compared to uninjured controls (g = 0.38, 95% CI [0.00, 0.77]). MT were greater in the involved limb (g = 0.93, 95% CI [- 0.01, 1.88]) and uninvolved limb (g = 0.57, 95% CI [0.13, 1.02]) compared to uninjured controls. MEP amplitudes in the involved limb were lesser compared to uninjured controls when evaluated more than 24 months after ACLR (g = -1.11, 95% CI [- 2.03, - 0.20]).

CONCLUSIONS

The available evidence supports that there are neural excitability differences within the corticospinal tract in individuals with ACLR when compared to uninjured controls. Future research should focus further on longitudinal assessments of neural excitability prior to and following ACLR. Identifying interventions aimed to facilitate corticospinal excitability after ACLR appears to be warranted to improve quadriceps function.

TRIAL REGISTRATION

Registered through PROSPERO CRD42020158714.

Visuomotor therapy modulates corticospinal excitability in patients following anterior cruciate ligament reconstruction: A randomized crossover trial

BACKGROUND

Corticospinal adaptations have been observed following anterior cruciate ligament reconstruction around the time of returning to activity. These measures have been related to quadriceps strength deficits. Visuomotor therapy, combining motor control tasks with visual biofeedback, has been shown to increase corticospinal excitability. The purpose of this study was to assess the immediate changes of corticospinal excitability following a single session of visuomotor therapy in patients following anterior cruciate ligament reconstruction.

METHODS

This was a single blinded, sham-controlled crossover study. Ten patients following ACLR (8 Female, 26.1(6.2) years) completed assessments of quadriceps strength at approximately 4- and 6-months following anterior cruciate ligament reconstruction. At 6-months, quadriceps motor evoked potentials were assessed at 80%, 90%, 100%, 110%, 120%, 130%, 140%, and 150% of the patient's active motor threshold. Patients were randomized to receive a single session of visuomotor therapy(active) or passive motion(sham). Quadriceps motor evoked potentials were reassessed for treatment effect. Following a one-week washout period, all patients received the crossover intervention.

FINDINGS

Moderate to large increases in motor response following visuomotor therapy 90%(P = .008, r = 0.60), 110%(P = .038, r = 0.46), 120%(P = .021, r = 0.52), 130%(P = .021, r = 0.52), 140%(P = .008, r = 0.60) and 150%(P = .021, r = 0.52) of the active motor threshold were found. Moderate increases in motor response was observed following the passive motion at 80% of the active motor threshold(P = .028, r = 0.49).

INTERPRETATION

A single session of visuomotor therapy was found to increase quadriceps corticospinal motor response greater than the response to sham therapy. Visuomotor therapy is a potential supplement to quadriceps rehabilitation programs when upregulation of corticospinal excitability is indicated.

Examining the Relationship Between Neuroplasticity and Learned Helplessness After ACLR: Early Versus Late Recovery

Context: Altered neural signaling is known to have a direct impact on psychological wellness. Therefore, disruptions in neural signaling after anterior cruciate ligament reconstruction may influence psychological dysfunction, in some cases manifesting as learned helplessness. Helplessness is a psychological paradigm that presents as altered neuromuscular control, reduced motivation, and psychological deficits. Objectives: The authors sought to evaluate the relationship between helplessness, neural activity, and quadriceps function at different time points after anterior cruciate ligament reconstruction. Evidence Acquisition: Twenty-nine individuals with unilateral anterior cruciate ligament reconstruction were categorized into early group (<2 y, age: 19.13 [2.18] y; height: 1.77 [0.11] m; mass: 76.903 [11.87] kg) or late group (>2 y, age: 22 [23] y; height: 1.67 [0.07] m; mass: 65.66 [11.33] kg). Quadriceps function (activation and strength), spinal-reflexive and corticospinal excitability (active motor thresholds and motor evoked potentials), and helplessness were obtained. A principal component analysis was performed by group (early and late) to identify which factors of helplessness were most associated with neural activity and quadriceps function. Pearson product moment correlation analyses were performed by group to determine associations between individual components and main outcomes. Evidence Synthesis: In the early group, cognitive readiness was associated with quadriceps strength of the injured limb (r2 = .513, P = .004), and self-awareness/management was associated with motor threshold of the injured limb (r2 = .238, P = .05). In the late group, intrinsic helplessness was associated with motor output of injured limb (r2 = .653, P = .01). Conclusion: Helplessness is made up of several attributional constructs, which are altered at different phases of recovery. Helplessness constructs interact differently with neural activity and quadriceps function across time. These findings are preliminary and do not establish a causal link between neural alterations and learned helplessness. Future studies should serially evaluate both changes in neural activity and learned helplessness attributes throughout recovery.

Efecto de la crioterapia en la articulación tibiotarsiana en el área de sección transversa del tibial anterior y el sóleo en ratas

Introducción. La crioterapia se usa para tratar la inflamación articular aguda, sin embargo su efecto sobre el músculo relacionado con la articulación inflamada aún no ha sido estudiado.Objetivo. Evaluar el efecto de la crioterapia sobre la articulación tibiotarsiana en el área de sección transversa (AST) de los músculos tibial anterior (TA) y sóleo en ratas con inflamación articular aguda.Materiales y métodos. Estudio experimental realizado en 32 ratas Wistar que fueron asignadas aleatoriamente a cuatro grupos: Control, Inflamación, Crioterapia-A y Crioterapia-B. El AST de las fibras de los músculos se midió 72 horas después de haberse iniciado el experimento.Resultados. En el tibial anterior hubo una reducción significativa del AST de las fibras musculares en los grupos Inflamación y Crioterapia-B en comparación con el grupo Control, mientras que en el grupo Crioterapia-A no se observó una reducción significativa en dicha área al compararlo con el Control. En el caso del músculo sóleo, se observó una reducción significativa del área en todos los grupos experimentales.Conclusión. El uso de crioterapia una vez al día por tres días atenúa el efecto atrófico de la inflamación articular aguda sobre el músculo TA, lo que confirma su importancia en el control del efecto deletéreo de la inflamación aguda sobre músculos de contracción rápida.

Single bout of vibration-induced hamstrings fatigue reduces quadriceps inhibition and coactivation of knee muscles after anterior cruciate ligament (ACL) reconstruction

Persistent quadriceps strength deficits in individuals with anterior cruciate ligament reconstruction (ACLr) have been attributed to arthrogenic muscle inhibition (AMI). The purpose of the present study was to investigate the effect of vibration-induced hamstrings fatigue on AMI in patients with ACLr. Eight participants with unilateral ACLr (post-surgery time: M = 46.5, SD = 23.5 months; age: M = 21.4, SD = 1.4 years) and eight individuals with no previous history of knee injury (age: M = 22.5, SD = 2.5 years) were recruited. A fatigue protocol, consisting of 10 min of prolonged local hamstrings vibration, was applied to both the ACLr and control groups. The central activation ratio (CAR) of the quadriceps was measured with a superimposed burst of electrical stimulation, and hamstrings/quadriceps coactivation was assessed using electromyography (EMG) during isometric knee extension exercises, both before and after prolonged local vibration. For the ACLr group, the hamstrings strength, measured by a load cell on a purpose-built chair, was significantly (P = 0.016) reduced about 14.5%, indicating fatigue was actually induced in the hamstrings. At baseline, the ACLr group showed a trend (P = 0.051) toward a lower quadriceps CAR (M = 93.2%, SD = 6.2% versus M = 98.1%, SD = 1.1%) and significantly (P = 0.001) higher hamstrings/quadriceps coactivation (M = 15.1%, SD = 6.2% versus M = 7.5%, SD = 4.0%) during knee extension compared to the control group. The fatigue protocol significantly (P = 0.001) increased quadriceps CAR (from M = 93.2%, SD = 6.2% to M = 97.9%, SD = 2.8%) and significantly (P = 0.006) decreased hamstrings/quadriceps coactivation during knee extension (from M = 15.1%, SD = 6.2% to M = 9.5%, SD = 4.5%) in the ACLr group. In conclusion, vibration-induced hamstrings fatigue can alleviate AMI of the quadriceps in patients with ACLr. This finding has clinical implications in the management of recovery for ACLr patients with quadriceps strength deficits and dysfunction.

Risk factors and the natural history of accelerated knee osteoarthritis: a narrative review

BACKGROUND

Osteoarthritis is generally a slowly progressive disorder. However, at least 1 in 7 people with incident knee osteoarthritis develop an abrupt progression to advanced-stage radiographic disease, many within 12 months. We summarize what is known - primarily based on findings from the Osteoarthritis Initiative - about the risk factors and natural history of accelerated knee osteoarthritis (AKOA) - defined as a transition from no radiographic knee osteoarthritis to advanced-stage disease < 4 years - and put these findings in context with typical osteoarthritis (slowly progressing disease), aging, prior case reports/series, and relevant animal models. Risk factors in the 2 to 4 years before radiographic manifestation of AKOA (onset) include older age, higher body mass index, altered joint alignment, contralateral osteoarthritis, greater pre-radiographic disease burden (structural, symptoms, and function), or low fasting glucose. One to 2 years before AKOA onset people often exhibit rapid articular cartilage loss, larger bone marrow lesions and effusion-synovitis, more meniscal pathology, slower chair-stand or walking pace, and increased global impact of arthritis than adults with typical knee osteoarthritis. Increased joint symptoms predispose a person to new joint trauma, which for someone who develops AKOA is often characterized by a destabilizing meniscal tear (e.g., radial or root tear). One in 7 people with AKOA onset subsequently receive a knee replacement during a 9-year period. The median time from any increase in radiographic severity to knee replacement is only 2.3 years. Despite some similarities, AKOA is different than other rapidly progressive arthropathies and collapsing these phenomena together or extracting results from one type of osteoarthritis to another should be avoided until further research comparing these types of osteoarthritis is conducted. Animal models that induce meniscal damage in the presence of other risk factors or create an incongruent distribution of loading on joints create an accelerated form of osteoarthritis compared to other models and may offer insights into AKOA.

CONCLUSION

Accelerated knee osteoarthritis is unique from typical knee osteoarthritis. The incidence of AKOA in the Osteoarthritis Initiative and Chingford Study is substantial. AKOA needs to be taken into account and studied in epidemiologic studies and clinical trials.

Using TENS to Enhance Therapeutic Exercise in Individuals with Knee Osteoarthritis

Transcutaneous electrical nerve stimulation (TENS) facilitates quadriceps voluntary activation in experimental settings. Augmenting therapeutic exercise (TE) with TENS may enhance the benefits of TE in individuals with knee osteoarthritis (KOA) and quadriceps voluntary activation failure (QVAF).

PURPOSE

This study aimed to determine the effect of TENS + TE on patient-reported function, quadriceps strength, and voluntary activation, as well as physical performance compared with sham TENS + TE (Sham) and TE alone in individuals with symptomatic KOA and QVAF.

METHODS

Ninety individuals participated in a double-blinded randomized controlled trial. Everyone received 10 standardized TE sessions of physical therapy. TENS + TE and Sham groups applied the respective devices during all TE sessions and throughout activities of daily living over 4 wk. The Western Ontario and McMaster University Osteoarthritis Index (WOMAC), quadriceps strength, and voluntary activation, as well as a 20-m walk test, chair-stand test, and stair-climb test were performed at baseline, after the 4-wk intervention (post 1) and at 8 wk after the start of the intervention (post 2). Mixed-effects models were used to determine between-group differences between baseline and post 1, as well as baseline and post 2.

RESULTS

Improvements in WOMAC subscales, quadriceps strength, and voluntary activation, 20-m walk times, chair-stand repetitions, and stair-climb time were found at post 1 and post 2 compared with baseline for all groups (P < 0.05). WOMAC Pain and Stiffness improved in the TENS + TE group compared with TE alone at post 1 (P < 0.05); yet, no other between-group differences were found.

CONCLUSIONS

TE effectively improved patient-reported function, quadriceps strength, and voluntary activation, as well as physical performance in individuals with symptomatic KOA and QVAF, but augmenting TE with TENS did not improve the benefits of TE.

The effect of a single high velocity low amplitude hip mobilization on strength in subjects with knee injuries

BACKGROUND

Manual therapy have been used as a disinhibitory intervention to increase muscle activation before performing functional tasks that are limited by weakness. Knee injuries are commonly associated with weakness in quadriceps and gluteus. Currently, there is no evidence to support anecdotal experience that a hip distraction mobilization improves muscle performance in subjects with knee injuries and lower extremity weakness.

OBJECTIVES

To determine if a hip distraction mobilization would result in an immediate change of maximal force output of the quadriceps and gluteus.

DESIGN

Non-controlled observational pre-post design.

METHODS

Forty individuals with knee pathology were included. Subjects underwent quadriceps, gluteus maximus, and gluteus medius muscle strength assessment before a single hip distraction of the symptomatic side. An immediate re-assessment of muscle strength of both symptomatic and asymptomatic sides followed the mobilization.

RESULTS

/findings: Comparing pre-to post-mobilization strength on the symptomatic side, a significant increase was found with the gluteus maximus (average change = 2.0 kg [95%CI 0.6-3.4]; p < 0.01) but not gluteus medius (0.2 kg [-0.7-1.0]; p = 0.71) or quadriceps (0.1 kg [-1.4-1.7]; p = 0.86). When comparing the strength on the symptomatic side in subjects with weakness greater than the MDD₉₅ (0.7-2.9 kg), a significant increase was again found for gluteus maximus (4.7 kg [2.6-6.8]; p < 0.01) but not for gluteus medius (0.2 kg [-1.0-1.4]; p = 0.71) or quadriceps (1.6 kg [-0.7-3.9]; p = 0.15).

CONCLUSION

A single hip distraction resulted in a significant increase in gluteus maximus strength but did not produce a change in gluteus medius or quadriceps strength in subjects with knee injuries.

Alterations in physical and neurocognitive wellness across recovery after ACLR: A preliminary look into learned helplessness

OBJECTIVES

Neural alterations after anterior cruciate ligament reconstruction (ACLR) may initiate a maladaptive neurocognitive response (learned helplessness [LH]). Understanding the interrelationships between neural inhibition, quadriceps function and psychological responses can provide clinicians areas to target during recovery. The purpose was to longitudinally evaluate neural excitability, strength and self-reported LH after ACL injury and to explore the relationship between these measures and knee mechanics and patient reported function.

DESIGN

Case-series.

SETTING

University.

PARTICIPANTS

Eight patients were evaluated across recovery after ACL injury.

MAIN OUTCOME MEASURES

Neural activity, quadriceps function, and self-reported LH were evaluated at pre-surgery, 3-months post-ACLR and at the time of return to play (RTP).

RESULTS

Patients presented with higher helplessness between 3-months and RTP. Neural excitability and quadriceps function were variable and associated with various aspects of LH. These findings indicate a systemic inability to generate appropriate neural signaling to the quadriceps and highlights how these changes may influence perceived helplessness and overall function after ACLR.

CONCLUSIONS

LH is related to both measures of physical function and neural outcomes and varies across recovery. This may provide clinicians with a feasible clinical tool that has the potential to identify a variety of impairments arising after ACLR.

A prospective randomized trial examining the use of a closed suction drain shows no influence on strength or function in primary total knee arthroplasty

Aims

The aim of this study was to determine whether closed suction drain (CSD) use influences recovery of quadriceps strength and to examine the effects of drain use on secondary outcomes: quadriceps activation, intra-articular effusion, bioelectrical measure of swelling, range of movement (ROM), pain, and wound healing complications.

Patients and Methods

A total of 29 patients undergoing simultaneous bilateral total knee arthroplasty (TKA) were enrolled in a prospective, randomized blinded study. Patients were randomized to receive a CSD in one limb while the contralateral limb had the use of a subcutaneous drain (SCDRN) without the use of suction (‘sham drain’). Isometric quadriceps strength was collected as the primary outcome. Secondary outcomes consisted of quadriceps activation, intra-articular effusion measured via ultrasound, lower limb swelling measured with bioelectrical impendence and limb girth, knee ROM, and pain. Outcomes were assessed preoperatively and postoperatively at day two, two and six weeks, and three months. Differences between limbs were determined using paired Student’s t-tests or Wilcoxon’s signed-rank tests.

Results

No significant differences were identified between limbs prior to surgery for the primary or secondary outcomes. No significant differences in quadriceps strength were seen between CSD and SCDRN limbs at postoperative day two (p = 0.09), two weeks (primary endpoint) (p = 0.7), six weeks (p = 0.3), or three months (p = 0.5). The secondary outcome of knee extension ROM was significantly greater in the CSD limb compared with the SCDRN (p = 0.01) at two weeks following surgery, but this difference was absent at all other intervals. Secondary outcomes of quadriceps activation, intra-articular effusion, lower limb swelling, and pain were not found to differ significantly at any timepoint following surgery.

Conclusion

The use of CSD during TKA did not influence quadriceps strength, quadriceps activation, intra-articular effusion, lower limb swelling, ROM, or pain. These results have limited drain use by the authors in primary uncomplicated TKA. Cite this article: Bone Joint J 2019;101-B (7 Supple C):84–90

Deficits in Quadriceps Force Control After Anterior Cruciate Ligament Injury: Potential Central Mechanisms

CONTEXT

Poor quadriceps force control has been observed after anterior cruciate ligament (ACL) reconstruction but has not been examined after ACL injury. Whether adaptations within the central nervous system are contributing to these impairments is unknown.

OBJECTIVE

To examine quadriceps force control in individuals who had sustained a recent ACL injury and determine the associations between cortical excitability and quadriceps force control in these individuals.

DESIGN

Cross-sectional study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Eighteen individuals with a recent unilateral ACL injury (6 women, 12 men; age = 29.6 ± 8.4 years, height = 1.74 ± 0.07 m, mass = 76.0 ± 10.4 kg, time postinjury = 69.5 ± 42.5 days) and 18 uninjured individuals (6 women, 12 men; age = 29.2 ± 6.8 years, height = 1.79 ± 0.07 m, mass = 79.0 ± 8.4 kg) serving as controls participated.

MAIN OUTCOME MEASURE(S)

Quadriceps force control was quantified as the root mean square error between the quadriceps force and target force during a cyclical force-matching task. Cortical excitability was measured as the active motor threshold and cortical silent period. Outcome measures were determined bilaterally in a single testing session. Group and limb differences in quadriceps force control were assessed using mixed analyses of variance (2 × 2). Pearson product moment correlations were performed between quadriceps force control and cortical excitability in individuals with an ACL injury.

RESULTS

Individuals with an ACL injury exhibited greater total force-matching error with their involved (standardized mean difference [SMD] = 0.8) and uninvolved (SMD = 0.9) limbs than did controls (F_1,27 = 11.347, P = .03). During the period of descending force, individuals with an ACL injury demonstrated greater error using their involved (SMD = 0.8) and uninvolved (SMD = 0.8) limbs than uninjured individuals (F_1,27 = 4.941, P = .04). Greater force-matching error was not associated with any cortical excitability measures (P > .05).

CONCLUSIONS

Quadriceps force control was impaired bilaterally after recent ACL injury but was not associated with selected measures of cortical excitability. The findings highlight a need to incorporate submaximal-force control tasks into rehabilitation and "prehabilitation," as the deficits were present before surgery.

The relationship between lower extremity swelling, quadriceps strength, and functional performance following total knee arthroplasty

BACKGROUND

The relationships between swelling after total knee arthroplasty (TKA) and quadriceps strength and functional performance are poorly understood. Therefore, the aim of this study was to examine the relationships between lower extremity swelling, measured using bioelectrical impedance assessment (SF-BIA), and quadriceps strength and timed up and go (TUG) times following TKA.

METHODS

53 participants (64 ± 9.5 y/o, 43% male) undergoing primary unilateral TKA were recruited for the longitudinal observational study with repeated measures. Quantities of swelling were examined for contribution to two and six-week outcomes of strength and TUG time using hierarchical regression controlling for age, sex, and the baseline value of the dependent variable. Swelling was assessed using bioelectrical impedance assessment and quantified as the peak level of swelling and cumulative swelling (integral) over the post-TKA time window. Maximum isometric quadriceps strength (MVIC) was measured using a electromechanical dynamometer and participant functional performance measured using the TUG.

RESULTS

Neither peak swelling nor cumulative swelling significantly contributed to the variance of two-week quadriceps strength. At six weeks, peak swelling significantly improved the variance in maximal quadriceps strength by an additional four percent (p = 0.05), while cumulative swelling did not significantly contribute. Peak swelling significantly contributed to the variance in two-week (16%) and six-week (five percent) TUG times (p < 0.05), but the cumulative swelling did not.

CONCLUSIONS

Peak swelling represents a value of post-TKA swelling that is associated with strength and function. Reducing the peak level of swelling, occurring early after surgery, may improve patient functional recovery.

LEVEL OF EVIDENCE

Level II - Prospective observational study.

Corticospinal excitability can discriminate quadriceps strength indicative of knee function after ACL-reconstruction

PURPOSE

To investigate relationships between quadriceps strength and neural activity, and to establish a clinical threshold of corticospinal excitability able to discriminate between patients with quadriceps strength indicative of satisfactory and unsatisfactory knee function after ACLR.

METHODS

A total of 29 patients following primary, unilateral ACL-reconstruction (11 female, 23.2 ± 8.1 years of age, 7.3 ± 2.5 months since surgery) participated. Subjective knee function was quantified using the International Knee Documentation Committee (IKDC) subjective evaluation. Peak isokinetic knee extensor torque was assessed at 90°/s. Quadriceps corticospinal excitability was quantified via active motor threshold (AMT, %2-Tesla) using transcranial magnetic stimulation during a 5% maximal voluntary isometric contraction of the quadriceps. Pearson's r correlations were used to assess the relationship between peak knee extensor torque and AMT. Receiver operating characteristic (ROC) curves were used to establish a threshold of (a) mass-normalized peak knee extensor torque to discriminate satisfactory knee function (IKDC ≥ 75.9%), and (b) AMT to discriminate quadriceps strength indicative of satisfactory knee function. Likelihood ratios (LR) and the magnitude of change in pre-post-test probability were calculated for each threshold.

RESULTS

Active motor threshold was negatively correlated with mass-normalized peak knee extensor torque (r = -0.503, P = 0.005). Knee extensor torque ≥1.23 Nm/kg was an excellent discriminator of satisfactory knee function (AUC = 0.890, P = 0.002; (+)LR = 9.56). An AMT ≤50.5% was an excellent discriminator of quadriceps strength indicative of satisfactory knee function following ACLR (AUC = 0.839, P = 0.005; (+)LR = 23.75).

CONCLUSION

Lower corticospinal excitability was associated with lower quadriceps strength. An AMT above 50.5% was found to decrease the probability of having satisfactory knee strength by over 62%.

Development of a reference chart to monitor postoperative swelling following total knee arthroplasty

Title: Development of a reference chart to monitor postoperative swelling following total knee arthroplasty.Purpose: Lower extremity swelling is a feature of total knee arthroplasty. Until recently, clinicians lacked tools to accurately measure swelling in clinical settings, but bioelectrical impedance assessment has shown promise in this regard. The purpose of this study was to develop a reference chart of lower extremity swelling following total knee arthroplasty.Method: Fifty-six participants (54% male, mean age = 64 years) were followed for the first 7 weeks following total knee arthroplasty, during which frequent lower extremity bioelectrical impedance assessments were performed. Using Generalized Additive Models for Location Scale and Shape, a reference chart for swelling was developed with bioelectrical impedance assessment data from the first 40 patients enrolled in the study (223 observations) and preliminarily tested for performance in the remaining 16 patients' data (96 observations).Results: The reference chart illustrates approximately 10% per day increase for the first 3 days following surgery. Peak swelling occurs 6-8 days following surgery; the 10th percentile demonstrates a peak of 25%, whereas the 90th percentile peaks at 47%. In the test data, this reference chart demonstrated accurate coverage at each estimated centile.Conclusion: The reference chart provides a novel framework for monitoring swelling following total knee arthroplasty and may augment clinical decisions to improve postoperative swelling management.Implications for rehabilitationThe use of bioelectrical impedance assessment provides an accurate and easily implemented approach for rehabilitation professionals to measure swelling.The reference chart provided allows for monitoring of patient recovery of swelling following total knee arthroplasty.Precise depictions of where a patient's swelling is in reference to others will improve clinical decision making at the individual level.

Corticospinal and intracortical excitability differ between athletes early after ACLR and matched controls

Neuromuscular impairments, such as quadriceps weakness and activation deficits, persist after anterior cruciate ligament reconstruction (ACLR). Recent research demonstrating changes in the function of the primary motor cortex after ACLR posits that quadriceps impairments may be influenced by reduced corticospinal excitability. The purpose of this study was to investigate whether the integrity of the neuromotor axis of the vastus medialis is altered in subjects 2 weeks post-ACLR compared to uninjured control subjects. Eighteen athletes 2 weeks post-ACLR and 18 age and sex matched uninjured control subjects participated in this cross-sectional study. We quantified corticospinal (resting motor threshold, RMT; motor evoked potential amplitudes at 120% RMT, MEP₁₂₀ ) and intracortical (inhibition and facilitation) excitability using single and paired pulse transcranial magnetic stimulation (TMS), respectively. We assessed spinal-reflex excitability (H-reflex amplitude normalized to maximal M-wave, H/M ratio) using peripheral stimulation. Subjects post-ACLR had higher RMTs (p = 0.001), greater MEP₁₂₀ amplitudes (p = 0.001), and more asymmetric facilitation (p = 0.041) than the uninjured control subjects. No significant group differences were found for intracortical inhibition (p = 0.289) and H/M ratio (p = 0.332). Our findings indicate that both intracortical and corticospinal excitability of vastus medialis are bilaterally altered in subjects 2 weeks after ACLR. Given persistent neuromuscular deficits seen after ACLR, rehabilitation strategies targeting intracortical and corticospinal deficits may potentially improve clinical outcomes. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2941-2948, 2018.

Is muscle strength in a painful limb affected by knee pain status of the contralateral limb? - Data from the Osteoarthritis Initiative

Contralateral knee pain has been suggested to be associated with muscle weakness in a pain-free knee, potentially through a mechanism of central nervous inhibition. Whether contralateral knee pain also affects muscle strength in a painful knee, however, is unknown. Here we study the extent to which isometric muscle strength differs between matched painful limbs of people with unilateral knee pain vs. matched painful limbs people with bilateral knee pain. To that end, 163 participants with unilateral knee pain were identified from the Osteoarthritis Initiative. Unilaterally painful (UP) limbs were defined as having numerical rating scale (NRS) ≥4/10, infrequent/frequent pain in the painful limb, while contralateral pain-free limbs were defined by NRS=0-1, no/infrequent pain and Western Ontario and McMaster Universities Arthritis Index (WOMAC) ≤1. The comparator group were matched bilaterally painful (BP) limbs. Maximum isometric muscle strength (N) was compared between 1:1 matched BP and UP limbs. Extensor strength was found to be lower in BP limbs than in UP limbs, (-2.9%; p=0.39) but this difference was not statistically significant. Extensor strength was significantly lower in the UP vs. contralateral pain-free limbs (-6.2%; p<0.001). No differences were observed between BP and contralateral painful limbs (0.6%; p=0.87). In conclusion, the current results identify a slight reduction of maximum knee extensor strength in a painful limb, when the contralateral knee is also painful. In contrast to pain-free limbs, this effect did not reach statistical significance, but the overall findings support the concept of central nervous inhibition of muscle strength by contralateral knee pain.

Clinical course and recommendations for patients after anterior cruciate ligament injury and subsequent reconstruction: A narrative review

Almost all athletes who have suffered an anterior cruciate ligament (ACL) injury expect a full return to sports at the same pre-injury level after ACL reconstruction (ACLR). Detailed patient information on the reasonable outcomes of the surgery may be essential to improve patient satisfaction.

Pre-operative rehabilitation before ACLR should be considered as an addition to the standard of care to maximise functional outcomes after ACLR.

We propose an optimised criterion-based rehabilitation programme within a biopsychosocial framework.

No benchmark exists for evaluating return-to-sport (RTS) readiness after ACLR. Therefore, the authors propose a multi-factorial RTS test battery. A combination of both physical and psychological elements should be included in the RTS test battery.

There is need for shared decision-making regarding RTS.

Cite this article: EFORT Open Rev 2017;2:410-420. DOI: 10.1302/2058-5241.2.170011

Persistent Muscle Inhibition after Anterior Cruciate Ligament Reconstruction: Role of Reflex Excitability

PURPOSE

Persistent voluntary quadriceps activation deficits are common after anterior cruciate ligament reconstruction (ACLR), but the direct causes are unclear. The primary purpose of this study was to determine whether spinal reflex excitability deficits are present in individuals with a history of ACLR, and secondarily to determine whether spinal reflex excitability predicts which individuals possess full voluntary quadriceps activation.

METHODS

One hundred and forty-seven individuals (74 healthy and 73 ACLR) participated in this cross-sectional case-control study. Quadriceps spinal reflex excitability was quantified using the Hoffmann reflex normalized to the maximal muscle response (H:M ratio). Voluntary quadriceps activation was evaluated with the burst superimposition technique and calculated via the central activation ratio (CAR). Separate 2 × 2 ANCOVA tests were used to compare between-limb and between-group differences for H:M ratio and CAR. A receiver operating characteristic curve was used to determine the accuracy of H:M ratio to predict if ACLR participants present with full voluntary activation (CAR ≥ 0.95).

RESULTS

The ACLR H:M ratio was not different between limbs or compared with the healthy group (P > 0.05). Although ACLR CAR was lower bilaterally compared with the healthy group (P < 0.001), it did not differ between limbs. The H:M ratio has poor accuracy for predicting which individuals exhibit full voluntary activation (receiver operating characteristic area under the curve = 0.52, 95% CI = 0.37,0.66; odds ratio = 2.2, 95% CI = 0.8, 5.9).

CONCLUSIONS

Spinal reflex excitability did not differ between limbs in individuals with ACLR or compared with healthy participants. The level of quadriceps spinal reflex excitability has poor accuracy at predicting which ACLR individuals would demonstrate full voluntary quadriceps activation.

Eccentric Exercise to Enhance Neuromuscular Control

Context:

Neuromuscular alterations are a major causal factor of primary and secondary injuries. Though injury prevention programs have experienced some success, rates of injuries have not declined, and after injury, individuals often return to activity with functionality below clinical recommendations. Considering alternative therapies to the conventional concentric exercise approach, such as one that can target neuromuscular injury risk and postinjury alterations, may provide for more effective injury prevention and rehabilitation protocols.

Evidence Acquisition:

Peer-reviewed sources available on the Web of Science and MEDLINE databases from 2000 through 2016 were gathered using searches associated with the keywords eccentric exercise, injury prevention, and neuromuscular control.

Hypothesis:

Eccentric exercise will reduce injury risk by targeting specific neural and morphologic alterations that precipitate neuromuscular dysfunction.

Study Design:

Clinical review.

Level of Evidence:

Level 4.

Results:

Neuromuscular control is influenced by alterations in muscle morphology and neural activity. Eccentric exercise beneficially modifies several underlying factors of muscle morphology (fiber typing, cross-sectional area, working range, and pennation angle), and emerging evidence indicates that eccentric exercise is also beneficial to peripheral and central neural activity (alpha motorneuron recruitment/firing, sarcolemma activity, corticospinal excitability, and brain activation).

Conclusion:

There is mounting evidence that eccentric exercise is not only a therapeutic intervention influencing muscle morphology but also targets unique alterations in neuromuscular control, influencing injury risk.

Benefits of using transcranial magnetic stimulation as a tool to facilitate the chronic knee injury rehabilitation

[Purpose] While primary motor cortex activation has been implicated as a key factor in the arthrogenic muscle inhibition after knee joint injury, no viable rehabilitation protocol has been developed to accommodate this factor. In this study, transcranial magnetic stimulation was applied as a means of dissipating arthrogenic muscle inhibition by introducing temporary motor cortex excitation prior to the rehabilitation. [Subjects and Methods] Twenty-four subjects who have underwent the surgery due to knee injury were recruited, and randomly assigned to the control or the simulation groups. The levels of electromyography signals during the maximum voluntary contraction of the quadriceps muscle before, during, and after training designed for the quadriceps strength rehabilitation were measured. [Results] When compared to controls, subjects who received the transcranial magnetic stimulations showed significantly increased levels of voluntary muscle contraction after the training. Moreover, the beneficial effect of the stimulation increased as the rehabilitation progressed. [Conclusion] Transcranial magnetic stimulation itself does not directly improve the symptoms related to knee injuries. However, the use of this technique can provide a time window for effective intervention by dissipating the unwanted effect of the arthrogenic muscle inhibition during rehabilitation.

Hamstring Contracture After ACL Reconstruction Is Associated With an Increased Risk of Cyclops Syndrome

Background:

Cyclops syndrome is characterized by loss of terminal knee extension due to proliferative fibrous nodule formation in the intercondylar notch. This complication occurs in the early postoperative period after anterior cruciate ligament reconstruction (ACLR). The pathogenesis of Cyclops syndrome is not well understood.

Hypothesis:

Persistent hamstring contracture after ACLR is associated with an increased risk of subsequent Cyclops syndrome.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

The files of 45 patients who underwent arthroscopic debridement of a Cyclops lesion after ACLR were analyzed. Recorded data included demographic information and technical details of surgery. Preoperative magnetic resonance images were also analyzed, and patients with femoral bone bruising were identified. Passive and active range of motion were recorded in all patients preoperatively and at 3 and 6 weeks after surgery to address the Cyclops lesion. Passive extension deficit was evaluated in comparison with the contralateral limb and classified as secondary to hamstring contracture when contracture was observed and palpated in the prone position and when the extension deficit was reversed after exercises performed to fatigue the hamstrings. A control group was selected using a random numbers table among our entire ACLR cohort. Statistical analysis was performed to analyze differences between the 2 groups.

Results:

There was no significant difference between the groups with regard to age at ACLR, sex distribution, time from injury to surgery (P > .05), proportion of professional athletes, presence of femoral bone bruise, or technical aspects of surgery. The overall extension deficit incidence was significantly higher in the Cyclops group at 3 weeks (Cyclops, 71%; control, 22%) (P < .001) and at 6 weeks (Cyclops, 60%; control, 7%) (P < .001). The extension deficit related to hamstring contracture was significantly higher in the Cyclops group at 3 weeks (Cyclops, 58%; control, 22%) (P < .001) and at 6 weeks (Cyclops, 29%; control, 2%) (P < .001).

Conclusion:

The Cyclops lesion is associated with a persistent hamstring contracture at 3 and 6 weeks after ACLR.

Quadriceps cortical adaptations in individuals with an anterior cruciate ligament injury

BACKGROUND

Altered quadriceps corticomotor excitability has been demonstrated following anterior cruciate ligament (ACL) injury and reconstruction, however only the single joint vasti muscles have been assessed. There is no current data on rectus femoris corticomotor excitability following ACL injury, the biarticular quadriceps muscle also critical for force attenuation and locomotion. The purpose of this study was to examine rectus femoris corticomotor excitability, intracortical inhibition and cortical motor representation in individuals with and without an ACL injury.

METHODS

A cross-sectional design was used to evaluate corticomotor excitability bilaterally in individuals with a physician confirmed ACL injury (12 males, six females; mean±SD age: 29.6±8.4years; BMI: 24.8±2.3kg·m(2); 69.5±42.5days post-injury) compared to a healthy control group (12 males, six females; age: 29.2±6.8years; BMI: 24.6±2.3kg·m(2)). Single-pulse transcranial magnetic stimulation (TMS) was used to assess corticomotor excitability and cortical motor representation, and paired-pulse TMS used to assess intracortical inhibition for rectus femoris while participants maintained a knee extension force at 10% of body weight.

RESULTS

The cortical silent period (cSP) duration was longer in the injured limb of the ACL group compared to the uninjured limb (P=0.004). No significant differences were found for corticomotor excitability, intracortical inhibition or cortical motor representation center position and size (P>0.05).

CONCLUSIONS

There is preliminary evidence that the cSP is longer, but changes in rectus femoris corticomotor excitability and cortical motor representation are not present following ACL injury.

Whole-Body and Local Muscle Vibration Immediately Improve Quadriceps Function in Individuals With Anterior Cruciate Ligament Reconstruction

OBJECTIVE

To determine the immediate effects of a single session of whole-body vibration (WBV) and local muscle vibration (LMV) on quadriceps function in individuals with anterior cruciate ligament reconstruction (ACLR).

DESIGN

Singe-blind, randomized crossover trial.

SETTING

Research laboratory.

PARTICIPANTS

Population-based sample of individuals with ACLR (N=20; mean age ± SD, 21.1±1.2y; mean mass ± SD, 68.3±14.9kg; mean time ± SD since ACLR, 50.7±21.3mo; 14 women; 16 patellar tendon autografts, 3 hamstring autografts, 1 allograft).

INTERVENTIONS

Participants performed isometric squats while being exposed to WBV, LMV, or no vibration (control). Interventions were delivered in a randomized order during separate visits separated by 1 week.

MAIN OUTCOME MEASURES

Quadriceps active motor threshold (AMT), motor-evoked potential (MEP) amplitude, Hoffmann reflex (H-reflex) amplitude, peak torque (PT), rate of torque development (RTD), electromyographic amplitude, and central activation ratio (CAR) were assessed before and immediately after a WBV, LMV, or control intervention.

RESULTS

There was an increase in CAR (+4.9%, P=.001) and electromyographic amplitude (+16.2%, P=.002), and a reduction in AMT (-3.1%, P<.001) after WBV, and an increase in CAR (+2.7%, P=.001) and a reduction in AMT (-2.9%, P<.001) after LMV. No effect was observed after WBV or LMV in H-reflex, RTD, or MEP amplitude. AMT (-3.7%, P<.001), CAR (+5.7%, P=.005), PT (+.31Nm/kg, P=.004), and electromyographic amplitude (P=.002) in the WBV condition differed from the control condition postapplication. AMT (-3.0% P=.002), CAR (+3.6%, P=.005), and PT (+.30Nm/kg, P=.002) in the LMV condition differed from the control condition postapplication. No differences were observed between WBV and LMV postapplication in any measurement.

CONCLUSIONS

WBV and LMV acutely improved quadriceps function and could be useful modalities for restoring quadriceps strength in individuals with knee pathologies.

The Consequence of a Medial Ankle Sprain on Physical and Self-reported Functional Limitations: A Case Study Over a 5-Month Period

STUDY DESIGN

Case report.

BACKGROUND

Little evidence exists about impairments and perceived disability following eversion injury to the deltoid ligament. This case study prospectively examined the neuromuscular, biomechanical, and psychological consequences of a case of a medial ankle sprain.

CASE DESCRIPTION

A recreationally active man with a history of a lateral ankle sprain (grade I) was participating in a university Institutional Review Board-approved research study examining the neuromuscular and mechanical characteristics associated with chronic ankle instability. Twenty-two days after the testing session, the participant sustained an eversion injury to his left ankle while playing basketball. Outcomes The outcomes of this case are presented using the International Classification of Functioning, Disability and Health model. Outcome variables were assessed at preinjury (medial ankle sprain), 3 months postinjury, and 5 months postinjury. Measurements included neural excitability of the soleus, balance assessment, joint stability, and psychological assessments. Data from this case study revealed that a medial ankle sprain reduces joint mobility and alters neural excitability of the soleus, with concurrent deficits in balance and self-reported function. These impairments forced the participant to downgrade his physical activity lifestyle up to 5 months postinjury.

DISCUSSION

These data suggest the need for the development of intervention strategies to address impairments in neural excitability and joint mobility at the ankle to help patients meet the goal of maintaining long-term joint health.

LEVEL OF EVIDENCE

Prognosis, level 4.

Effects of transcutaneous electrical nerve stimulation on quadriceps function in individuals with experimental knee pain

Knee joint pain (KJP) is a cardinal symptom in knee pathologies, and quadriceps inhibition is commonly observed among KJP patients. Previously, KJP independently reduced quadriceps strength and activation. However, it remains unknown how disinhibitory transcutaneous electrical nerve stimulation (TENS) will affect inhibited quadriceps motor function. This study aimed at examining changes in quadriceps maximum voluntary contraction (MVC) and central activation ratio (CAR) before and after sensory TENS following experimental knee pain. Thirty healthy participants were assigned to either the TENS or placebo groups. All participants underwent three separate data collection sessions consisting of two saline infusions and one no infusion control in a crossover design. TENS or placebo treatment was administered to each group for 20 min. Quadriceps MVC and CAR were measured at baseline, infusion, treatment, and post-treatment. Perceived knee pain intensity was measured on a 100-mm visual analogue scale. Post-hoc analysis revealed that hypertonic saline infusion significantly reduced the quadriceps MVC and CAR compared with control sessions (P < 0.05). Sensory TENS, however, significantly restored inhibited quadriceps motor function compared with placebo treatment (P < 0.05). There was a negative correlation between changes in MVC and knee pain (r = 0.33, P < 0.001), and CAR and knee pain (r = 0.62, P < 0.001), respectively.

Neural Excitability Alterations After Anterior Cruciate Ligament Reconstruction

CONTEXT

Neuromuscular dysfunction is common after anterior cruciate ligament reconstruction (ACL-R). However, little is known about quadriceps spinal-reflex and descending corticomotor excitability after ACL-R. Understanding the effects of ACL-R on spinal-reflex and corticomotor excitability will help elucidate the origins of neuromuscular dysfunction.

OBJECTIVE

To determine whether spinal-reflex excitability and corticomotor excitability differed between the injured and uninjured limbs of patients with unilateral ACL-R and between these limbs and the matched limbs of healthy participants.

DESIGN

Case-control study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 28 patients with unilateral ACL-R (9 men, 19 women; age = 21.28 ± 3.79 years, height = 170.95 ± 10.04 cm, mass = 73.18 ± 18.02 kg, time after surgery = 48.10 ± 36.17 months) and 29 participants serving as healthy controls (9 men, 20 women; age = 21.55 ± 2.70 years, height = 170.59 ± 8.93 cm, mass = 71.89 ± 12.70 kg) volunteered.

MAIN OUTCOME MEASURE(S)

Active motor thresholds (AMTs) were collected from the vastus medialis (VM) using transcranial magnetic stimulation. We evaluated VM spinal reflexes using the Hoffmann reflex normalized to maximal muscle responses (H : M ratio). Voluntary quadriceps activation was measured with the superimposed-burst technique and calculated using the central activation ratio (CAR). We also evaluated whether ACL-R patients with high or low voluntary activation had different outcomes.

RESULTS

The AMT was higher in the injured than in the uninjured limb in the ACL-R group (t27 = 3.32, P = .003) and in the matched limb of the control group (t55 = 2.05, P = .04). The H : M ratio was bilaterally higher in the ACL-R than the control group (F1,55 = 5.17, P = .03). The quadriceps CAR was bilaterally lower in the ACL-R compared with the control group (F1,55 = 10.5, P = .002). The ACL-R group with low voluntary activation (CAR < 0.95) had higher AMT than the control group (P = .02), whereas the ACL-R group with high voluntary activation (CAR ≥ 0.95) demonstrated higher H : M ratios than the control group (P = .05).

CONCLUSIONS

The higher VM AMT in the injured limbs of ACL-R patients suggested that corticomotor deficits were present after surgery. Higher bilateral H : M ratios in ACL-R patients may be a strategy to reflexively increase excitability to maintain voluntary activation.

Quadriceps corticomotor excitability following an experimental knee joint effusion

PURPOSE

Deficits in quadriceps strength and voluntary activation are common following knee injury. These deficits are hypothesized to generate from a neural level, however, it remains unclear how corticomotor pathways are affected following acute injury. The purpose of this investigation was to examine whether corticomotor alterations of the quadriceps were present following a simulated knee joint injury using an experimental effusion model.

METHODS

Participants completed two testing sessions, an experimental knee effusion and control session, separated by 7 days. The central activation ratio was used to assess change in quadriceps activation. Corticomotor excitability was assessed pre- and post-intervention via active motor thresholds (AMTs) and motor evoked potentials (MEPs) normalized to maximal muscle responses. MEPs were assessed at different percentages of AMT, and associated slopes between these percentages were analysed. Paired-sample t tests were performed on percentage change scores calculated from pre-intervention outcome measures to assess change in corticomotor excitability and changes in the slope of MEP values as percentage of AMT increased.

RESULTS

Quadriceps activation significantly decreased during the effusion session. AMT and MEP change scores were not different between effusion and control conditions. No substantial differences were found in slope between any percentages of AMT.

CONCLUSIONS

An experimental knee effusion did not induce changes in corticomotor excitability. Further research is needed to understand how corticomotor pathways are affected following joint injury. Corticomotor excitability alterations may not be the cause of acute changes in neuromuscular activation following joint effusion. Future research should determine whether clinically altering corticomotor excitability will improve physical function.

LEVEL OF EVIDENCE

II.

Is Pain in One Knee Associated with Isometric Muscle Strength in the Contralateral Limb?: Data From the Osteoarthritis Initiative

OBJECTIVE

Knee pain and muscle weakness confer risk for knee osteoarthritis incidence and progression. The purpose of this study was to determine whether unilateral knee pain influences contralateral thigh muscle strength.

DESIGN

Of 4796 Osteoarthritis Initiative participants, 224 (mean ± SD age, 63.9 ± 8.9 yrs) cases could be matched to a control. Cases were defined as having unilateral knee pain (numerical rating scale, ≥ 4/10; ≥infrequent pain) and one pain-free knee (numerical rating scale, 0-1; ≤infrequent pain; Western Ontario and McMaster Universities Arthritis Index, ≤ 1). Controls were defined as having bilaterally pain-free knees (numerical rating scale, 0-1; ≤infrequent pain; Western Ontario and McMaster Universities Arthritis Index, ≤ 1). Maximal isometric muscle strength (N) was compared between limbs in participants with unilateral pain (cases) as well as between pain-free limbs of cases and controls.

RESULTS

Knee extensor/flexor strength in pain-free limbs of the cases was lower than that in bilaterally pain-free controls (-5.5%/-8.4%; P = 0.043/P = 0.022). Within the cases, maximum extensor/flexor strength was significantly lower in the painful limb than in the pain-free limb (-6.3%/4.1%; P < 0.0001/P = 0.015).

CONCLUSIONS

These results suggest that strength in limbs without knee pain is associated with the pain status of the contralateral knee. The strength difference between unilateral pain-free cases and matched bilateral pain-free controls was similar to that between limbs in persons with unilateral knee pain. Lower strength caused by contralateral knee pain might be centrally mediated.

Quadriceps neural alterations in anterior cruciate ligament reconstructed patients: A 6-month longitudinal investigation

The purpose of this investigation was to evaluate differences in quadriceps corticospinal excitability, spinal-reflexive excitability, strength, and voluntary activation before, 2 weeks post and 6 months post-anterior cruciate ligament reconstruction (ACLr). This longitudinal, case-control investigation examined 20 patients scheduled for ACLr (11 females, 9 males; age: 20.9 ± 4.4 years; height:172.4 ± 7.5 cm; weight:76.2 ± 11.8 kg) and 20 healthy controls (11 females, 9 males; age:21.7 ± 3.7 years; height: 173.7 ± 9.9 cm; weight: 76.1 ± 19.7 kg). Maximal voluntary isometric contractions (MVIC), central activation ratio (CAR), normalized Hoffmann spinal reflexes, active motor threshold (AMT), and normalized motor-evoked potential (MEP) amplitudes at 120% of AMT were measured in the quadriceps muscle at the specific time points. ACLr patients demonstrated bilateral reductions in spinal-reflexive excitability compared with controls before surgery (P = 0.02) and 2 weeks post-surgery (P ≤ 0.001). ACLr patients demonstrated higher AMT at 6 months post-surgery (P ≤ 0.001) in both limbs. No MEP differences were detected. Quadriceps MVIC and CAR were lower in both limbs of the ACLr group before surgery and 6 months post-surgery (P ≤ 0.05) compared with controls. Diminished excitability of spinal-reflexive and corticospinal pathways are present at different times following ACLr and occur in combination with clinical deficits in quadriceps strength and activation. Early rehabilitation strategies targeting spinal-reflexive excitability may help improve postoperative outcomes, while later-stage rehabilitation may benefit from therapeutic techniques aimed at improving corticospinal excitability.

Clinical strategies for addressing muscle weakness following knee injury

Muscle strength is a determinate of physical function and increasing muscle strength is an important clinical goal for patients with knee injury. This article discusses the emerging evidence regarding a novel rehabilitation strategy that uses disinhibitory modalities to increase neuromuscular activation in conjunction with traditional muscle strengthening for the purpose of maximizing strength gains following acute knee injury or surgery and in patients with knee osteoarthritis. The use of disinhibitory modalities and specific types of neuromuscular training for clinically maximizing strength are discussed.

Changes in voluntary quadriceps activation predict changes in muscle strength and gait biomechanics following knee joint effusion

BACKGROUND

It has been hypothesized that arthrogenic muscle inhibition is responsible for altering physical function following knee injury. The association between the onset of arthrogenic muscle inhibition, measured using voluntary quadriceps activation, and changes in muscle strength and gait biomechanics are unknown.

METHODS

Outcomes were collected before and following a 60 ml experimental knee effusion in eighteen healthy participants. Voluntary quadriceps activation was the predictor variable, while the criterion variable included, maximal voluntary isometric strength, peak knee flexion angle, peak internal knee extension moment, and peak vertical ground reaction forces during the first half of stance phase upon stair descent. Percent change scores (Δ) were imputed into linear regression equations to determine associations between predictor and criterion variables.

FINDINGS

The variance in Δ voluntary quadriceps activation significantly predicted 87% the variance in the Δ strength (R(2)=0.87, P<0.001; Δ strength=-2.15+1.77Δ voluntary quadriceps activation) and 25% of the Δ vertical ground reaction force following effusion (R(2)=0.25, P=0.04; Δ vertical ground reaction force=-6.1+0.57 Δ voluntary quadriceps activation). After accounting for Δ knee flexion angle, Δ voluntary quadriceps activation predicted an additional 29% (Δ R(2)=0.29, P=0.007) of the variance in the Δ knee extension moment (R(2)=0.54, P=0.003, Δ knee extension moment=-10.79+0.74Δ knee flexion angle+1.64Δ voluntary quadriceps activation) following knee effusion.

INTERPRETATION

Immediate quadriceps activation deficits following joint effusion result in immediate alterations in muscle strength, knee extensor moment and vertical ground reaction force during gait.

Quadriceps function following ACL reconstruction and rehabilitation: implications for optimisation of current practices

PURPOSE

To determine the most effective practices for quadriceps strengthening after ACL reconstruction.

METHODS

An electronic search has been performed for the literature appearing from January 1990 to January 2012. Inclusion criteria were articles written in English, German or Dutch with unilateral ACL-reconstructed patients older than 13 years, RCT rehabilitation programmes containing muscle strengthening, protocol described in detail and time frame of measurements reported. Quadriceps muscle strength and patient-reported outcomes were the endpoints. Included studies were assessed on their methodological quality using the CONSORT Checklist.

RESULTS

From 645 identified studies, 10 met the inclusion criteria. Seven studies found an increase in quadriceps strength after intervention programmes regardless of type of training. An eccentric exercise programme showed significantly better values for isometric quadriceps strength compared to a concentric exercise programme. The Tegner activity scale showed a significant increase in activity level for all training programmes. The Cincinnati Knee Rating System showed significant improvements in particular for the neuromuscular training group.

CONCLUSIONS

The evidence from this review indicates that eccentric training may be most effective to restore quadriceps strength, but full recovery may not be achieved with current rehabilitation practices. Neuromuscular training incorporating motor learning principles should be added to strengthening training to optimise outcome measurements.

LEVEL OF EVIDENCE

II.

Manual therapy directed at the knee or lumbopelvic region does not influence quadriceps spinal reflex excitability

Manual therapies, directed to the knee and lumbopelvic region, have demonstrated the ability to improve neuromuscular quadriceps function in individuals with knee pathology. It remains unknown if manual therapies may alter impaired spinal reflex excitability, thus identifying a potential mechanism in which manual therapy may improve neuromuscular function following knee injury.

AIM

To determine the effect of local and distant mobilisation/manipulation interventions on quadriceps spinal reflex excitability.

METHODS

Seventy-five individuals with a history of knee joint injury and current quadriceps inhibition volunteered for this study. Participants were randomised to one of five intervention groups: lumbopelvic manipulation (grade V), lumbopelvic manipulation positioning (no thrust), grade IV patellar mobilisation, grade I patellar mobilisation, and control (no treatment). Changes in spinal reflex excitability were quantified by assessing the Hoffmann reflex (H-reflex), presynaptic, and postsynaptic excitability. A hierarchical linear-mixed model for repeated measures was performed to compare changes in outcome variables between groups over time (pre, post 0, 30, 60, 90 min).

RESULTS

There were no significant differences in H-reflex, presynaptic, or postsynaptic excitability between groups across time.

CONCLUSIONS

Manual therapies directed to the knee or lumbopelvic region did not acutely change quadriceps spinal reflex excitability. Although manual therapies may improve impairments and functional outcomes the underlying mechanism does not appear to be related to changes in spinal reflex excitability.

Disinhibitory interventions and voluntary quadriceps activation: a systematic review

OBJECTIVE

To determine the effects of various therapeutic interventions on increasing voluntary quadriceps muscle activation.

BACKGROUND

Decreased voluntary quadriceps activation is commonly associated with knee injury. Recently, research has focused on developing specific disinhibitory interventions to improve voluntary quadriceps activation; yet, it remains unknown which interventions are most effective in promoting this improvement.

DATA SOURCES

We searched Web of Science from January 1, 1965 through September 27, 2012, using the key words quadriceps activation and transcutaneous electrical nerve stimulation, transcranial magnetic stimulation, cryotherapy, focal joint cooling, joint mobilization, joint mobilisation, joint manipulation, manual therapy, and neuromuscular electrical stimulation.

STUDY SELECTION

Studies evaluating the effect of disinhibitory interventions on volitional quadriceps activation were used in our review. Standardized effect sizes (Cohen d) and 95% confidence intervals (CIs) were calculated from voluntary quadriceps activation means and standard deviations measured at baseline and at all available postintervention time points from each study.

DATA SYNTHESIS

Ten studies were grouped into 5 categories based on intervention type: manual therapy (4 studies), transcutaneous electrical nerve stimulation (2 studies), cryotherapy (2 studies), neuromuscular electrical stimulation (2 studies), and transcranial magnetic stimulation (1 study). Transcutaneous electrical nerve stimulation demonstrated the strongest immediate effects (d = 1.03; 95% CI = 0.06, 1.92) and long-term effects (d = 1.93; 95% CI = 0.91, 2.83). Cryotherapy (d = 0.76; 95% CI = -0.13, 1.59) and transcranial magnetic stimulation (d = 0.54; 95% CI = -0.33, 1.37) had moderate immediate effects in improving voluntary quadriceps activation, whereas manual therapy (d = 0.38; 95% CI = -0.35, 1.09) elicited only weak immediate effects. Neuromuscular electrical stimulation produced weak negative to strong positive effects (range of d values = -0.50 to 1.87) over a period of 3 weeks to 6 months.

CONCLUSIONS

Transcutaneous electrical nerve stimulation demonstrated the strongest and most consistent effects in increasing voluntary quadriceps activation and may be the best disinhibitory intervention for improving the same.

Chronic ankle instability and corticomotor excitability of the fibularis longus muscle

CONTEXT

Neuromuscular deficits are common in people with chronic ankle instability (CAI). Corticomotor pathways are very influential in the production of voluntary muscle function, yet these pathways have not been evaluated in people with CAI.

OBJECTIVE

To determine if corticomotor excitability of the fibularis longus (FL) differs between individuals with unilateral CAI and matched control participants without CAI.

DESIGN

Case-control study.

SETTING

Laboratory. Patients or Other Participants: Ten people with CAI (4 men, 6 women; age = 21.2 ± 1.23 years, height = 175.13 ± 9.7 cm, mass = 77.1 ± 13.58 kg) and 10 people without CAI (4 men, ± women; age = 21.2 ± 2.3 years; height = 172.34 ± 8.86 cm, mass = 73.4 ± 7.15 kg) volunteered for this study.

MAIN OUTCOME MEASURE(S)

Transcranial magnetic stimulation was performed over the motor cortex on neurons corresponding with the FL. All testing was performed with the participant in a seated position with a slightly flexed knee joint and the ankle secured in 10 8 of plantar flexion. The resting motor threshold (RMT), which was expressed as a percentage of 2 T, was considered the lowest amount of magnetic energy that would induce an FL motor evoked potential equal to or greater than 20 l V, as measured with surface electromyography, on 7 consecutive stimuli. In addition, the Functional Ankle Disability Index (FADI) and FADI Sport were used to assess self-reported function.

RESULTS

Higher RMTs were found in the injured and uninjured FL of the CAI group (60.8% ± 8.4% and 59.1% ± 8.99%, respectively) than the healthy group (52.8% ± 8.56% and 52% ± 7.0%, respectively; F(1,18) = 4.92, P = .04). No leg x group interactions (F(1,18) = 0.1, P = .76) or between-legs differences (F(1,18) = 0.74, P = .40) were found. A moderate negative correlation was found between RMT and FADI (r = 0.4, P = .04) and FADI Sport (r = 0.44, P = .03), suggesting that higher RMT is related to lower self-reported function.

CONCLUSIONS

Higher bilateral RMTs may indicate deficits in FL corticomotor excitability in people with CAI. In addition, a moderate correlation between RMT and FADI suggests that cortical excitability deficits may be influential in altering function.