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

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.

The effects of repetitive haemarthrosis on postural balance in children with haemophilia

Sensory information from visual, vestibular and proprioceptive systems is necessary to control posture and balance. Impairment in proprioception due to repetitive joints bleeding may lead to a deficit in postural balance which, in turn, leads to high joint stress and risk of bleeding recurrence. Despite the increase in attention in this field during the past few years, the data concerning to how bleeds can affect postural control in children with haemophilia (CWH) remain scarce. This study aimed to evaluate the postural balance in CWH. Twenty CWH Haemophilia Group (HG) and 20 age-matched children Control Group (CG) were recruited to this study. A force plate was used to record centre of pressure (COP) displacement under four different postural conditions during quiet standing: eyes open on firm surface, eyes open on foam surface, eyes closed on firm surface and eyes closed on a foam surface. Variables of COP as sway area and mean velocity and in anterior-posterior (y) medio-lateral (x) direction were processed and for each variable sensory, quotients were calculated and compared between groups. No differences were found in visual and vestibular quotients variables between groups. A higher value was found in sway area variable on proprioception quotient in the HG when compared with CG (P = 0.042). CWH with repetitive joint bleed on lower limbs showed differences in postural balance when compared with non-haemophiliac children. The identification of early balance impairments in CWH can help us understand better the effects of bleeds inside joints on postural control and plan a more effective preventive and rehabilitative treatment.

Arthrogenic neuromusculature inhibition: a foundational investigation of existence in the hip joint

BACKGROUND

Patients and athletes with diminished gluteal muscle activation are thought to have 'gluteal inhibition'. This may be a component of arthrogenic neuromuscular inhibition, which has been well documented in the knee and generalized to all joints. While clinical evidence surrounding gluteal inhibition increases, supportive research is non-existent. This study investigated whether arthrogenic neuromuscular inhibition occurred about the hip following instillation of intra-articular fluid during functional hip extension tasks.

METHODS

Data was collected in a biomechanics laboratory (control) and hospital setting (intervention). Nine healthy individuals (4M/5F) comprised the control group. The intervention group contained twelve patients (4M/8F) with hip pathology requiring a magnetic resonance arthrogram (capsular distension via intra-articular fluid injection) procedure. The participants performed a pelvic bridge (PB) and active hip extension (EXT) before and after the control time or injection. Peak EMG from the gluteus maximus (GM) was collected bilaterally.

FINDINGS

The findings of this study provide substantial support for arthrogenic inhibition following hip intra-articular fluid instillation during functional tasks. Two-way repeated measures ANOVA revealed a significant group by session interaction effect (PB,EXT: affected/unaffected=0.0192/0.9654 P=0.05, <0.0001/0.0826 P=0.05). Tukey post hoc revealed decreases in ipsilateral peak GM EMG following intervention were significant (0.0238/<0.0001 P=0.025). No changes were observed in the control group.

INTERPRETATION

These concepts are of clinical importance to both patient and athletic populations. Understanding the role of gluteal inhibition in the injury process is essential to the development of rehabilitation and prevention protocols. Restoration and promotion of optimal recruitment patterns are crucial to enhancing athletic performance.

Electrode type and placement configuration for quadriceps activation evaluation

CONTEXT

The ability to accurately estimate quadriceps voluntary activation is an important tool for assessing neuromuscular function after a variety of knee injuries. Different techniques have been used to assess quadriceps volitional activation, including various stimulating electrode types and electrode configurations, yet the optimal electrode types and configurations for depolarizing motor units in the attempt to assess muscle activation are unknown.

OBJECTIVE

To determine whether stimulating electrode type and configuration affect quadriceps central activation ratio (CAR) and percentage-of-activation measurements in healthy participants.

DESIGN

Crossover study.

SETTING

Research laboratory.

PATIENTS AND OTHER PARTICIPANTS

Twenty participants (13 men, 7 women; age = 26 ± 5.3 years, height = 173.85 ± 7.3 cm, mass = 77.37 ± 16 kg) volunteered.

INTERVENTION(S)

All participants performed 4 counter-balanced muscle activation tests incorporating 2 different electrode types (self-adhesive, carbon-impregnated) and 2 electrode configurations (vastus, rectus).

MAIN OUTCOME MEASURE(S)

Quadriceps activation was calculated with the CAR and percentage-of-activation equations, which were derived from superimposed burst and resting torque measurements.

RESULTS

No differences were found between conditions for CAR and percentage-of-activation measurements, whereas resting twitch torque was higher in the rectus configuration for both self-adhesive (216 ± 66.98 Nm) and carbon-impregnated (209.1 ± 68.22 Nm) electrodes than in the vastus configuration (209.5 ± 65.5 Nm and 204 ± 62.7 Nm, respectively) for these electrode types (F(1,19) = 4.87, P = .04). In addition, resting twitch torque was greater for both electrode configurations with self-adhesive electrodes than with carbon-impregnated electrodes (F(1,19) = 9.33, P = .007). Bland-Altman plots revealed acceptable mean differences for agreement between electrode type and configuration for CAR and percentage of activation, but limits of agreement were wide.

CONCLUSIONS

Although these electrode configurations and types might not necessarily be able to be used interchangeably, differences in electrode type and configuration did not seem to affect CAR and percentage-of-activation outcome measures.

Changes in voluntary quadriceps activation predict changes in quadriceps strength after therapeutic exercise in patients with knee osteoarthritis

INTRODUCTION

Recent rehabilitation paradigms have suggested that improving voluntary muscle activation may optimize strength outcomes related to resistance training. The aim of this study was to determine if changes in voluntary quadriceps activation could predict changes in quadriceps strength following a 4 week therapeutic exercise regimen.

METHOD

Thirty-six participants with tibiofemoral osteoarthritis volunteered for this study, while 30 participants (14 males, 16 females, 58 ± 11.8 years, 172.2 ± 9.2 cm, 87.1 ± 18.5 kg) finished the 4 week supervised therapeutic exercise protocol and were used in the final analysis. Demographics, quadriceps strength and voluntary quadriceps activation using the burst superimposition technique were evaluated prior to the intervention. Following the therapeutic exercise program, quadriceps strength and voluntary activation were assessed. Simple correlations were performed to determine covariates in a multiple regression equation to evaluate if changes in voluntary quadriceps activation could predict changes in quadriceps strength.

RESULTS

There was a significant moderate simple correlation between participant height and change in MVIC (r=-0.44, P=0.01). Both height and changes in voluntary quadriceps activation significantly predicted changes in MVIC (R(2)=0.66, P<0.001). After controlling for patient height, a change in voluntary quadriceps activation produced a significant improvement in the prediction of a change in MVIC (ΔR(2)=0.47, P<0.001).

DISCUSSION

Changes in voluntary quadriceps activation predicted 47% of variance in the change in quadriceps strength. These results suggest that interventions aimed at manipulating quadriceps activation may be helpful for improving quadriceps strength in patients with tibiofemoral osteoarthritis.

A theoretical framework for understanding neuromuscular response to lower extremity joint injury

Background:

Neuromuscular alterations are common following lower extremity joint injury and often lead to decreased function and disability. These neuromuscular alterations manifest in inhibition or abnormal facilitation of the uninjured musculature surrounding an injured joint. Unfortunately, these neural alterations are poorly understood, which may affect clinical recognition and treatment of these injuries. Understanding how these neural alterations affect physical function may be important for proper clinical management of lower extremity joint injuries.

Methods:

Pertinent articles focusing on neuromuscular consequences and treatment of knee and ankle injuries were collected from peer-reviewed sources available on the Web of Science and Medline databases from 1975 through 2010. A theoretical model to illustrate potential relationships between neural alterations and clinical impairments was constructed from the current literature.

Results:

Lower extremity joint injury affects upstream cortical and spinal reflexive excitability pathways as well as downstream muscle function and overall physical performance. Treatment targeting the central nervous system provides an alternate means of treating joint injury that may be effective for patients with neuromuscular alterations.

Conclusions:

Disability is common following joint injury. There is mounting evidence that alterations in the central nervous system may relate to clinical changes in biomechanics that may predispose patients to further injury, and novel clinical interventions that target neural alterations may improve therapeutic outcomes.

Immediate Effects of Acupuncture and Cryotherapy on Quadriceps Motoneuron Pool Excitability: Randomised Trial Using Anterior Knee Infusion Model

Objective

The authors asked the following research questions: will an anterior knee infusion model induce constant pain? will perceived pain alter motoneuron pool (MNP) excitability? and will treatments alter perceived pain and/or MNP excitability?

Methods

Thirty-six neurologically healthy volunteers participated in this randomised controlled laboratory study. To induce anterior knee pain (AKP), 5% hypertonic saline (0.12 ml/min with a total volume of 8.5 ml over 70 min) was injected into the infrapatellar fat pad of the dominant leg. One of four 30-min treatments was randomly assigned to each subject after pain was induced (acupuncture, cryotherapy, sham cryotherapy and no treatment). Five acupuncture needles (SP9, SP10, ST36, GB34 and an ah shi point) were inserted to a depth of 1 cm. Vastus medialis (VM) maximum Hoffmann reflexes normalised by maximum motor response were recorded from each subject at baseline, 20 min post-injection, 50 min post-injection and 70 min post-injection. To record pain perception, a visual analogue scale was used every 5 min after injection.

Results

An anterior knee infusion pain model increased perceived pain (p<0.0001). No change was found in VM MNP excitability among the four treatments (p<0.19) or at any of the time intervals (p<0.52). Cryotherapy reduced perceived pain compared with acupuncture (p=0.0003) and sham treatment (p=0.0002).

Conclusions

A pain model may be used in other neurophysiological intervention studies related to AKP. AKP alone may not directly alter quadriceps activation. None of the treatments altered VM MNP excitability. Cryotherapy reduced pain while a single session of acupuncture and sham treatments did not.

Longitudinal changes in the lower extremity functional scale after anterior cruciate ligament reconstructive surgery

OBJECTIVE

To describe the pattern of change in lower extremity physical function status as measured by the Lower Extremity Functional Scale (LEFS) during the first 16 weeks after anterior cruciate ligament (ACL) reconstructive surgery and illustrate how this information can be applied in clinical practice to assist with goal setting and the evaluation of patient outcomes. The secondary objective is to estimate the test-retest reliability of the LEFS in this population.

DESIGN

Prospective cohort, observational.

SETTING

Physiotherapy private practice.

PATIENTS

Forty-seven participants underwent ACL reconstructive surgery and were initially recruited. Two participants were excluded from the analysis, resulting in 45 participants (28 men, mean age 29.4 years; 17 women, mean age 29.0 years).

INTERVENTIONS

Participants underwent a rehabilitation protocol.

MAIN OUTCOME MEASURES

Participants completed the LEFS at each visit from their initial physiotherapy session to 16 weeks postsurgery. A nonlinear model of change was developed, which related LEFS scores to weeks postsurgery. Test-retest reliability was examined between the seventh and ninth weeks using intraclass correlation coefficients (ICC2,1) and standard error of measurement (SEM).

RESULTS

The nonlinear model demonstrated rapid improvements in LEFS scores within the first 7 to 8 weeks with a gradual tapering of this improvement. At 16 weeks, the predicted LEFS score was 63 out of a maximum score of 80. The LEFS demonstrated excellent test-retest reliability in this population (ICC2,1 = 0.90, SEM = 3.7).

CONCLUSIONS

This study provides a description of postsurgical change in functional status for patients after ACL reconstructive surgery that can assist clinicians in developing clinical goals.

CLINICAL RELEVANCE

A rapid improvement in lower extremity physical function is demonstrated in the first 7 to 8 weeks after ACL reconstructive surgery with a tapering of this improvement after 8 weeks.

Effect of knee joint icing on knee extension strength and knee pain early after total knee arthroplasty: a randomized cross-over study

OBJECTIVE

To investigate the acute effect of knee joint icing on knee extension strength and knee pain in patients shortly after total knee arthroplasty.

DESIGN

A prospective, single-blinded, randomized, cross-over study.

SETTING

A fast-track orthopaedic arthroplasty unit at a university hospital.

PARTICIPANTS

Twenty patients (mean age 66 years; 10 women) scheduled for primary unilateral total knee arthroplasty.

INTERVENTIONS

The patients were treated on two days (day 7 and day 10) postoperatively. On one day they received 30 minutes of knee icing (active treatment) and on the other day they received 30 minutes of elbow icing (control treatment). The order of treatments was randomized.

MAIN OUTCOME MEASURES

Maximal knee extension strength (primary outcome), knee pain at rest and knee pain during the maximal knee extensions were measured 2-5 minutes before and 2-5 minutes after both treatments by an assessor blinded for active or control treatment.

RESULTS

The change in knee extension strength associated with knee icing was not significantly different from that of elbow icing (knee icing change (mean (1 SD)) -0.01 (0.07) Nm/kg, elbow icing change -0.02 (0.07) Nm/kg, P = 0.493). Likewise, the changes in knee pain at rest (P = 0.475), or knee pain during the knee extension strength measurements (P = 0.422) were not different between treatments.

CONCLUSIONS

In contrast to observations in experimental knee effusion models and inflamed knee joints, knee joint icing for 30 minutes shortly after total knee arthroplasty had no acute effect on knee extension strength or knee pain.

Reduced quadriceps motor-evoked potentials in an individual with unilateral knee osteoarthritis: a case report

One male with unilateral osteoarthritis (OA) of the knee underwent testing of corticospinal (CS) excitability (as quantified from motor-evoked potentials (MEPs) in the rectus femoris (RF) using transcranial magnetic stimulation) and quadriceps muscle strength. Baseline data indicated reduced MEP amplitudes in the RF of the affected limb compared to the unaffected limb. Increases in RF MEP amplitudes from both limbs were observed immediately following a 30-minute exercise session focusing on muscle strengthening. Following an 8-week muscle strengthening intervention, the participant exhibited increased MEP amplitudes and muscle strength in the affected limb. These findings suggest that alterations in peripheral muscle function found in patients with knee OA may have an origin centrally within the motor cortex and that interlimb differences may be evident in those with unilateral disease. These findings also suggest that CS excitability may be improved following a muscle strengthening intervention.

Transcranial magnetic stimulation and volitional quadriceps activation

CONTEXT

Quadriceps-activation deficits have been reported after meniscectomy. Transcranial magnetic stimulation (TMS) in conjunction with maximal contractions affects quadriceps activation in patients after meniscectomy.

OBJECTIVE

To determine the effect of single-pulsed TMS on quadriceps central activation ratio (CAR) in patients after meniscectomy.

DESIGN

Randomized controlled clinical trial.

SETTING

University laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty participants who had partial meniscectomy and who had a CAR less than 85% were assigned randomly to the TMS group (7 men, 4 women; age  =  38.1 ± 16.2 years, height  =  176.8 ± 11.5 cm, mass  =  91.8 ± 27.5 kg, postoperative time  =  36.7 ± 34.9 weeks) or the control group (7 men, 2 women; age  =  38.2 ± 17.5 years, height  =  176.5 ± 7.9 cm, mass  =  86.2 ± 15.3 kg, postoperative time  =  36.6 ± 37.4 weeks).

INTERVENTION(S)

Participants in the experimental group received TMS over the motor cortex that was contralateral to the involved leg and performed 3 maximal quadriceps contractions with the involved leg. The control group performed 3 maximal quadriceps contractions without the TMS.

MAIN OUTCOME MEASURE(S)

Quadriceps activation was assessed using the CAR, which was measured in 70° of knee flexion at baseline and at 0, 10, 30, and 60 minutes posttest. The CAR was expressed as a percentage of full activation.

RESULTS

Differences in CAR were detected over time (F(4,72)  =  3.025, P  = .02). No interaction (F(4,72)  =  1.457, P  =  .22) or between-groups differences (F(1,18)  =  0.096, P  =  .76) were found for CAR. Moderate CAR effect sizes were found at 10 (Cohen d  =  0.54, 95% confidence interval [CI]  =  -0.33, 1.37) and 60 (Cohen d  =  0.50, 95% CI  =  -0.37, 1.33) minutes in the TMS group compared with CAR at baseline. Strong effect sizes were found for CAR at 10 (Cohen d  =  0.82, 95% CI  =  -0.13, 1.7) and 60 (Cohen d  =  1.06, 95% CI  =  0.08, 1.95) minutes in the TMS group when comparing percentage change scores between groups.

CONCLUSIONS

No differences in CAR were found between groups at selected points within a 60-minute time frame, yet moderate to strong effect sizes for CAR were found at 10 and 60 minutes in the TMS group, indicating increased activation after TMS.

Relationship between transcranial magnetic stimulation and percutaneous electrical stimulation in determining the quadriceps central activation ratio

OBJECTIVE

To determine the relationship between quadriceps central activation ratios (CARs) derived from a percutaneous electrical stimulation (CAR(SIB)) and a transcranial magnetic stimulation (CAR(TMS)) in healthy participants.

DESIGN

Nineteen healthy participants (5 men, 14 women, 23.7 ± 4.8 yrs, 66.8 ± 10.0 kg, and 170.1 ± 7.0 cm) qualified for this descriptive study. Muscle activation, using both methods (CAR(SIB) and CAR(TMS)), was measured at days 1, 14, and 28. All participants performed both methods in a counterbalanced order. Correlation coefficients and Bland-Altman plots were used to assess relationships and agreement between the two methods. For both methods, reliability was assessed at 14 and 28 days using Bland-Altman plots and intraclass correlation coefficients.

RESULTS

CAR(TMS) scores were higher than CAR(SIB) scores for all three sessions, with mean differences between CAR scores of -0.06 (95% confidence interval, -0.19-0.07), -0.03 (95% confidence interval, -0.14-0.08), and -0.03 (95% confidence interval, -0.11-0.05). There was a significant moderate positive correlation between CAR(SIB) and CAR(TMS) at 14 days from baseline (ρ = 0.45, P = 0.05). Intersession reliability was strong for CAR(SIB) at 14 and 28 days from baseline (intraclass correlation coefficients = 0.80 [P = 0.001] and 0.85 [P < 0.001], respectively). Intersession reliability for CAR(TMS) was moderate from baseline to 14 days (intraclass correlation coefficients = 0.68 [P = 0.01]).

CONCLUSIONS

It does not seem that the CAR(TMS) and CAR(SIB) methods are interchangeable measurements for evaluating volitional quadriceps activation; however, both measurements seem to have acceptable agreement at 14 and 28 days compared with day 1.

Voluntary quadriceps activation deficits in patients with tibiofemoral osteoarthritis: a meta-analysis

The objective of this study was to assess the magnitude of quadriceps activation deficits in the involved extremity and contralateral extremity of patients with knee joint osteoarthritis (OA), as well as matched controls. An exhaustive search of the literature was performed using Web of Science between 1970 and February 24, 2010, using the search terms "osteoarthritis" AND "quadriceps activation" OR "quadriceps inhibition" and cross-referencing pertinent articles. Studies written in English reporting quadriceps activation means and standard deviations in patients with tibiofemoral OA via a method using an exogenous electrical stimulation were evaluated for methodological quality and were included for data analysis. Fourteen individual studies met the criteria for inclusion into data analysis. The number of participants and mean activation levels were used to calculate weighted means for the involved limb (14 studies), the contralateral limb (from a subset of 6 studies), and an involved limb subset from only the studies evaluating the contralateral limb and population of control subjects (5 studies). Weighted means from the involved limb (82.2; 95% CI = 81.4-83.3%), contralateral limb (81.7; 80.1-83.3%), and involved limb subset (76.8; 74.8-78.8%) groups were found to have lower volitional quadriceps activation compared with the control groups (90; 88.9-91.7%). Although the weighted involved limb mean was not different from that of the contralateral limb, the mean and 95% confidence intervals for the involved limb subset were lower than that of the contralateral limb group, suggesting that the involved limb had less volitional activation within OA subjects. This provides evidence that bilateral quadriceps volitional activation deficits are present in persons with knee OA.

Six weeks of balance training improves sensorimotor function in individuals with chronic ankle instability

STUDY DESIGN

Prospective cohort study.

OBJECTIVE

To assess the effect of 6 weeks of balance training on sensorimotor measures previously found to be deficient in participants with chronic ankle instability (CAI).

BACKGROUND

CAI is the tendency toward repeated ankle sprains and recurring symptoms, occurring in 40% to 70% of individuals who have previously sustained a lateral ankle sprain. Recent studies have found deficits in sensorimotor measures in individuals with CAI. As balance training is a common component of ankle rehabilitation, understanding its effect on the sensorimotorsystem in individuals with CAI may enable us to optimize protocols to better utilize this rehabilitation method.

METHODS

Twelve participants with CAI and 9 healthy volunteers participated. Independent variables were group (CAI, control) and time (pretraining, posttraining). Participants with CAI who completed a 6-week balance training program and healthy controls who did not get any training were pretested and posttested at the beginning and at the end of 6 weeks.

RESULTS

The individuals in the CAI group who performed balance training demonstrated better performance than control participants on baseline adjusted posttraining measures of dynamic balance in the anterior medial (P = .021), medial (P = .048), and posterior medial directions (P = .030); motoneuron pool excitability Hmax/Mmax ratio (P = .044) and single-limb presynaptic inhibition (P = .012); and joint position sense inversion variable error (P = .017). It may be of note that no systematic differences were detected for static balance or plantar flexion joint position sense tasks.

CONCLUSIONS

After 6 weeks of balance training, individuals with CAI demonstrated enhanced dynamic balance, inversion joint position sense, and changes in motoneuron pool excitability compared to healthy controls who did not train.

LEVEL OF EVIDENCE

Therapy, level 2b.

Effects of transcutaneous electrical nerve stimulation and therapeutic exercise on quadriceps activation in people with tibiofemoral osteoarthritis

STUDY DESIGN

Blinded, randomized controlled trial.

OBJECTIVES

To determine if the combination of transcutaneous electrical nerve stimulation (TENS) set to a sensory level and therapeutic exercise would be more effective than the combination of placebo TENS and therapeutic exercises or therapeutic exercises only to increase quadriceps activation in individuals with tibiofemoral osteoarthritis.

BACKGROUND

Quadriceps activation deficits are common in those with tibiofemoral osteoarthritis, and TENS has been reported to immediately increase quadriceps activation. Yet the long-term benefits of TENS for motor neuron activation have yet to be determined.

METHODS

Thirty-six individuals with radiographically assessed tibiofemoral osteoarthritis were randomly assigned to the TENS and exercise, placebo and exercise, and exercise only groups. All participants completed a supervised 4-week lower extremity exercise program. TENS and placebo TENS were worn throughout the therapeutic exercise sessions, as well as during daily activities. Our primary outcome measures, quadriceps central activation ratio, and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were evaluated at baseline and at 2 weeks and 4 weeks of the intervention.

RESULTS

Quadriceps activation was significantly higher in the TENS with exercise group compared to the exercise only group at 2 weeks (0.94 ± 0.04 versus 0.82 ± 0.12, P<.05) and the placebo and exercise group at 4 weeks (0.94 ± 0.06 versus 0.81 ± 0.15, P<.05). WOMAC scores improved in all 3 groups over time, with no significant differences among groups.

CONCLUSION

This study provides evidence that TENS applied in conjunction with therapeutic exercise and daily activities increases quadriceps activation in patients with tibiofemoral osteoarthritis and, while function improved for all participants, effects were greatest in the group treated with a combination of TENS and therapeutic exercises.

LEVEL OF EVIDENCE

Therapy, level 1b-.

Effects of disinhibitory transcutaneous electrical nerve stimulation and therapeutic exercise on sagittal plane peak knee kinematics and kinetics in people with knee osteoarthritis during gait: a randomized controlled trial

Objective: To determine whether sensory transcutaneous electrical nerve stimulation (TENS) augmented with therapeutic exercise and worn for daily activities for four weeks would alter peak gait kinetics and kinematics, compared with placebo electrical stimulation and exercise, and exercise only.

Design: Randomized controlled trial.

Setting: Motion analysis laboratory.

Subjects: Thirty-six participants with radiographically assessed knee osteoarthritis and volitional quadriceps activation below 90% were randomly assigned to electrical stimulation, placebo and comparison (exercise-only) groups.

Interventions: Participants in all three groups completed a four-week quadriceps strengthening programme directed by an experienced rehabilitation clinician. Active electrical stimulation units and placebo units were worn in the electrical stimulation and placebo groups throughout the rehabilitation sessions as well as during all activities of daily living.

Main measures: Peak external knee flexion moment and angle during stance phase were analysed at a comfortable walking speed before and after the intervention.

Findings: Comfortable walking speed increased for all groups over time (TENS 1.16 ± 0.15 versus 1.32 ± 0.16 m/s; placebo 1.21 ± 0.34 versus 1.3 ± 0.24 m/s; comparison 1.27 ± 0.18 versus 1.5 ± 0.14 m/s), yet no group differences in speed were found. No differences were found for peak flexion moment or angle between groups overtime.

Conclusions: TENS in conjunction with therapeutic exercise does not seem to affect peak flexion moment and angle during stance over a four-week period in participants with tibiofemoral osteoarthritis.

Introduction to rehabilitation

Rehabilitation plays an integral role when it comes to managing sports injuries in a safe and timely manner. Doing so competently allows for a greater chance of quick recovery and ultimate success on and off the field. Understanding the goals of rehabilitation and how to enhance communication between all providers who are involved with athlete care is critical to the process. The purpose of this article is to thoroughly explain the steps and critical components of a rehabilitation process designed specifically for each athlete's needs.

A neuromuscular mechanism of posttraumatic osteoarthritis associated with ACL injury

Anterior cruciate ligament (ACL) injury leads to early-onset osteoarthritis. Quadriceps weakness is a consequence of ACL injury and is considered to result from arthrogenic inhibition (AMI). AMI is the neurological "shutdown" of muscles surrounding an injured joint, preventing full activation, reducing strength, and promoting atrophy. As quadriceps function is critical for energy absorption, its dysfunction may contribute to posttraumatic osteoarthritis.

Sensorimotor function as a predictor of chronic ankle instability

BACKGROUND

Recurrent ankle injury occurs in 70% of individuals experiencing a lateral ankle sprain. The cause of this high level of recurrence is currently unknown. Researchers have begun to investigate sensorimotor deficits as one possible cause with inconclusive and often conflicting results. The purpose of this study was to further the understanding of the role of sensorimotor deficits in the chronically unstable ankle by establishing which specific measures best distinguish between chronically unstable and healthy ankles.

METHODS

Twenty-two participants with chronic ankle instability and 21 healthy matched controls volunteered. Twenty-five variables were measured within four sensorimotor constructs: joint kinesthesia (isokinetic dynamometer), static balance (force plate), dynamic balance (Star Excursion Balance Test) and motoneuron pool excitability (electromyography).

FINDINGS

The above variables were evaluated using a discriminant function analysis [Wilks'Lambda=0.536 chi(2)(7, N=43)=22.118, P=0.002; canonical correlation=0.681]. The variables found to be significant were then used to assess group discrimination. This study revealed that seven separate variables from the static balance (anterior/posterior and medial/lateral displacement and velocity) and motoneuron pool excitability constructs (single-legged recurrent inhibition and single- and double-legged paired reflex depression) accurately classified over 86% of participants with unstable ankles.

INTERPRETATION

These results suggest that a multivariate approach may be necessary to understand the role of sensorimotor function in chronic ankle instability, and to the development of appropriate rehabilitation and prevention programs. Out of the four overall constructs, only two were needed to accurately classify the participants into two groups. This indicates that static balance and motoneuron pool excitability may be more clinically important in treatment and rehabilitation of chronic ankle instability than functional balance or joint kinesthesia.

Effects of lumbopelvic joint manipulation on quadriceps activation and strength in healthy individuals

Lumbopelvic joint manipulation has been shown to increase quadriceps force output and activation, but the duration of effect is unknown. It is also unknown whether lower grade joint mobilisations may have a similar effect. Forty-two healthy volunteers (x+/-SD; age=28.3+/-7.3 yr; ht=172.8+/-9.8 cm; mass=76.6+/-21.7 kg) were randomly assigned to one of three groups (lumbopelvic joint manipulation, 1 min lumbar passive range of motion (PROM), or prone extension on elbows for 3 min). Quadriceps force and activation were measured using the burst-superimposition technique during a seated isometric knee extension task before and at 0, 20, 40, and 60 min following intervention. Collectively, all groups demonstrated a significant decrease (p<0.001) in quadriceps force output without changes in activation (p>0.05) at all time intervals following intervention. The group that received a lumbopelvic joint manipulation demonstrated a significant increase in quadriceps force (3%) and activation (5%) (p<0.05) immediately following intervention, but this effect was not present after the 20 min interval. Since participants in this study were free of knee joint pathology, it is possible that they did not have the capacity to allow for large changes in quadriceps muscle activation to occur.

Joint angle and contraction mode influence quadriceps motor neuron pool excitability

OBJECTIVE

The purpose of the study was to compare the central activation ratio (CAR) of eccentric contractions to isometric contractions at 30 and 70 degrees of knee flexion.

DESIGN

A repeated-measures design was used. CARs were measured at 30 and 70 degrees of knee flexion in 16 healthy subjects during both eccentric and isometric modes of contraction. CARs were measured using the superimposed burst technique.

RESULTS

Isometric CARs at 30 degrees (0.88+/-0.069) of knee flexion were significantly higher (P<0.001) than at 70 degrees (0.77+/-0.116). Eccentric CARs were significantly higher (P=0.013) at 70 degrees (0.87+/-0.085) of knee flexion compared with 30 degrees (0.8+/-0.09). At 30 degrees of knee flexion, isometric CARs were significantly higher (P=0.003) than eccentric CARs. At 70 degrees, eccentric CARs were higher (P<0.001) when compared with isometric CARs.

CONCLUSIONS

Our results provide evidence that isometric measures at a single joint angle are not sufficient in generalizing activation of an entire muscle group for dynamic movements. CARs are significantly affected by joint angle and mode of contraction.

Intra-articular anesthesia and knee muscle response

BACKGROUND

Many receptors located within the intra-articular knee structures contribute to the neuromuscular responses of the knee. The purpose was to compare the automatic postural response induced by a perturbation at the foot before and after an intra-articular injection of a local anesthetic (bupivicaine), after a saline (sham) injection, and after no intra-articular injection (control) in the knee.

METHODS

Muscle onset latencies and automatic response magnitudes for the vastus medialis, vastus lateralis, biceps femoris, medial hamstrings, tibialis anterior, and gastrocnemius were measured using electromyography (EMG) when anteriorly directed perturbations were applied to the feet of 30 subjects. All subjects then received a lidocaine skin injection followed by: an intra-articular bupivicaine injection (treatment group); an intra-articular saline injection (sham group); or no injection (control group), depending on their randomized group assignment. The perturbation tests were then repeated.

FINDINGS

Muscle onset latencies and automatic response magnitudes did not change as a result of the intra-articular injections. Latencies were significantly greater for the vastus medialis and vastus lateralis when compared to the medial hamstrings, biceps femoris and tibialis anterior (P<0.001). Automatic response magnitudes for the tibialis anterior were significantly greater than those of the hamstrings, which were greater than those of the quadriceps (P<0.001).

INTERPRETATION

There were no differences in muscle response when anteriorly directed perturbations were applied to the foot with or without an injection of local anesthetic in the knee. Intra-articular receptors were either unaffected by the anesthetic or the extra-articular receptors or receptors of the other joints were able to compensate for their loss.

Corticomotor excitability associated with unilateral knee dysfunction secondary to anterior cruciate ligament injury

In the present report, we investigated changes in corticomotor excitability associated with unilateral knee dysfunction secondary to anterior cruciate ligament (ACL) injury. Ten participants, each with a previous history of unilateral ACL injury (median time post-injury 22 months) and eight healthy controls underwent transcranial magnetic stimulation (TMS) to assess excitability of the lower limb motor representation. Resting motor thresholds (RMTs) and stimulus response curves were measured at rest, while amplitude of motor evoked potentials and silent period duration were measured during active contraction. Correlations between these indices of excitability and three clinical measures of knee function were identified. Paired comparisons of indices by hemisphere revealed an asymmetry only in RMTs, which were significantly reduced on the side of injury in the ACL group. Correlations with clinical measures showed that the extent of quadriceps motor representation, as reflected by the steepness of SR curves, was strongly associated with quadriceps strength (r 2=0.71) on the injured side. The RMT asymmetry reported here in the context of ACL injury is consistent with other recent reports describing enhanced excitability of corticomotor projections targeting muscles adjacent to an immobilized or a painful joint. In such conditions, alterations in the quantity and quality of sensory feedback from the affected limb may underlie the rise in cortical excitability.