Immediate Effects of Transcutaneous Electrical Nerve Stimulation and Focal Knee Joint Cooling on Quadriceps Activation

Can Arthrogenic Muscle Inhibition Exist in Peroneal Muscles Among People with Chronic Ankle Instability? A Cross-sectional Study

BACKGROUND

Ankle sprains lead to an unexplained reduction of ankle eversion strength, and arthrogenic muscle inhibition (AMI) in peroneal muscles is considered one of the underlying causes. This study aimed to observe the presence of AMI in peroneal muscles among people with chronic ankle instability (CAI).

METHODS

Sixty-three people with CAI and another sixty-three without CAI conducted maximal voluntary isometric contraction (MVIC) and superimposed burst (SIB) tests during ankle eversion, then fifteen people with CAI and fifteen without CAI were randomly invited to repeat the same tests to calculate the test-retest reliability. Electrical stimulation was applied to the peroneal muscles while the participants were performing MVIC, and the central activation ratio (CAR) was obtained by dividing MVIC torque by the sum of MVIC and SIB torques, representing the degree of AMI.

RESULTS

The intra-class correlation coefficients were 0.77 (0.45-0.92) and 0.92 (0.79-0.97) for the affected and unaffected limbs among people with CAI, and 0.97 (0.91-0.99) and 0.93 (0.82-0.97) for the controlled affected and unaffected limbs among people without CAI; Significant group × limb interaction was detected in the peroneal CAR (p = 0.008). The CARs were lower among people with CAI in the affected and unaffected limbs, compared with those without CAI (affected limb = 82.54 ± 9.46%, controlled affected limb = 94.64 ± 6.37%, p < 0.001; unaffected limb = 89.21 ± 8.04%, controlled unaffected limb = 94.93 ± 6.01%, p = 0.016). The CARs in the affected limbs were lower than those in the unaffected limbs among people with CAI (p = 0.023). No differences between limbs were found for CAR in the people without CAI (p = 0.10).

CONCLUSIONS

Bilateral AMI of peroneal muscles is observed among people with CAI. Their affected limbs have higher levels of AMI than the unaffected limbs.

The past and future of peri-operative interventions to reduce arthrogenic quadriceps muscle inhibition after total knee arthroplasty: A narrative review

Total knee arthroplasty (TKA) improves patient-reported function by alleviating joint pain, however the surgical trauma exacerbates already impaired muscle function, which leads to further muscle weakness and disability after surgery. This early postoperative strength loss indicates a massive neural inhibition and is primarily driven by a deficit in quadriceps muscle activation, a process known as arthrogenic muscle inhibition (AMI). To enhance acute recovery of quadriceps muscle function and long-term rehabilitation of individuals after TKA, AMI must be significantly reduced in the early post-operative period. The aim of this narrative review is to review and discuss previous efforts to mitigate AMI after TKA and to suggest new approaches and interventions for future efficacy evaluation. Several strategies have been explored to reduce the degree of post-operative quadriceps AMI and improve strength recovery after TKA by targeting post-operative swelling and inflammation or changing neural discharge. A challenge of this work is the ability to directly measure AMI and relevant contributing factors. For this review we focused on interventions that aimed to reduce post-operative swelling or improve knee extension strength or quadriceps muscle activation measured by twitch interpolation. For individuals undergoing TKA, the use of anti-inflammatory medications, tranexamic acid, cryotherapy, intra-articular drains, torniquets, and minimally invasive surgical techniques for TKA have limited benefit in attenuating quadriceps AMI early after surgery. However, interventions such as inelastic compression garments, voluntary muscle contractions, and neuro-muscular electrical stimulation show promise in mitigating or circumventing AMI and should continue to be refined and explored.

The effects of neuromuscular electrical stimulation to the ankle pronators on neural excitability & functional status in patients with chronic ankle instability

OBJECTIVES

Chronic ankle instability (CAI) is associated with decreased neural excitability that negatively impacts function. This study assessed a 2-week neuromuscular electrical stimulation (NMES) or transcutaneous electrical nerve stimulation (TENS) intervention over the ankle pronators on neural excitability, performance, and patient-reported function in patients with CAI.

STUDY DESIGN

Randomized controlled trial.

PARTICIPANTS

Twenty participants with CAI completed the study.

MAIN OUTCOME MEASURES

Participants were assessed for reflexive and corticospinal excitability to the ankle muscles, dynamic balance, side-hop test performance and patient-reported outcomes at baseline, post-intervention (2-weeks), and retention (4-weeks). Between baseline and post-intervention, participants reported for 5 sessions where they received either sub-noxious NMES (n = 11) or sensory-level TENS (n = 9) over the ankle pronators.

RESULTS

Improved reflexive excitability to the ankle pronators was observed in TENS at post-intervention (p = 0.030) and retention (p = 0.029). Cortical excitability to the dorsiflexors increased in TENS at post-intervention (p = 0.017), but not at retention (p = 0.511). No significant changes were found for other neural measures, balance ability, hopping, or patient-reported function (p > 0.050).

CONCLUSIONS

Our results suggest TENS modified neural excitability; however, these changes were not enough to impact clinical function. While TENS may be capable of neuromodulation, it may require rehabilitative exercise to generate lasting changes. NCT04322409.

LEVEL OF EVIDENCE

Level 2.

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.

Characterising the Features of 381 Clinical Studies Evaluating Transcutaneous Electrical Nerve Stimulation (TENS) for Pain Relief: A Secondary Analysis of the Meta-TENS Study to Improve Future Research

Background and Objectives: Characterising the features of methodologies, clinical attributes and intervention protocols, of studies is valuable to advise directions for research and practice. This article reports the findings of a secondary analysis of the features from studies screened as part of a large systematic review of TENS (the meta-TENS study). Materials and Methods: A descriptive analysis was performed on information associated with methodology, sample populations and intervention protocols from 381 randomised controlled trials (24,532 participants) evaluating TENS delivered at a strong comfortable intensity at the painful site in adults with pain, irrespective of diagnosis. Results: Studies were conducted in 43 countries commonly using parallel group design (n = 334) and one comparator group (n = 231). Mean ± standard deviation (SD) study sample size (64.05 ± 58.29 participants) and TENS group size (27.67 ± 21.90 participants) were small, with only 13 of 381 studies having 100 participants or more in the TENS group. Most TENS interventions were ‘high frequency’ (>10 pps, n = 276) and using 100 Hz (109/353 reports that stated a pulse frequency value). Of 476 comparator groups, 54.2% were active treatments (i.e., analgesic medication(s), exercise, manual therapies and electrophysical agents). Of 202 placebo comparator groups, 155 used a TENS device that did not deliver currents. At least 216 of 383 study groups were able to access other treatments whilst receiving TENS. Only 136 out of 381 reports included a statement about adverse events. Conclusions: Clinical studies on TENS are dominated by small parallel group evaluations of high frequency TENS that are often contaminated by concurrent treatment(s). Study reports tended focus on physiological and clinical implications rather than the veracity of methodology and findings. Previously published criteria for designing and reporting TENS studies were neglected and this should be corrected in future research using insights gleaned from this analysis.

Effect of transcutaneous electrical nerve stimulation (TENS) on knee pain and physical function in patients with symptomatic knee osteoarthritis: the ETRELKA randomized clinical trial

OBJECTIVE

To determine the effectiveness of TENS at relieving pain and improving physical function as compared to placebo TENS, and to determine its safety, in patients with knee osteoarthritis.

METHODS

Multi-centre, parallel, 1:1 randomized, double-blind, placebo-controlled clinical trial conducted in six outpatient clinics in Switzerland. We included 220 participants with knee osteoarthritis recruited between October 15, 2012, and October 15, 2014. Patients were randomized to 3 weeks of treatment with TENS (n = 108) or placebo TENS (n = 112). Our pre-specified primary endpoint was knee pain at the end of 3-weeks treatment assessed with the WOMAC pain subscale. Secondary outcome measures included WOMAC physical function subscale and safety outcomes.

RESULTS

There was no difference between TENS and placebo TENS in WOMAC pain at the end of treatment (mean difference -0.06; 95%CI -0.41 to 0.29; P = 0.74), nor throughout the trial duration (P = 0.98). Subgroup analyses did not indicate an interaction between patient/treatment characteristics and treatment effect on WOMAC pain at the end of treatment (P-interaction ≥0.22). The occurrence of adverse events was similar across groups, with 10.4% and 10.6% of patients reporting events in the TENS and placebo TENS groups, respectively (P = 0.95). No relevant differences were observed in secondary outcomes.

CONCLUSIONS

TENS does not improve knee osteoarthritis pain when compared to placebo TENS. Therapists should consider other potentially more effective treatment modalities to decrease knee osteoarthritis pain and facilitate strengthening and aerobic exercise. Our findings are conclusive and further trials comparing TENS and placebo TENS in this patient population are not necessary.

Effects of transcutaneous electrical nerve stimulation (TENS) in people with knee osteoarthritis: A systematic review and meta-analysis

OBJECTIVE

To evaluate the effects of Transcutaneous Electric Nerve Stimulation (TENS) on pain, function, walking ability and stiffness in people with Knee osteoarthritis (KOA).

DESIGN

Systematic review and meta-analysis of randomized controlled trials.

METHODS

We searched MEDLINE, EMBASE, PubMed, Cochrane Central Register of Controlled Trials, Physiotherapy Evidence Database (PEDro), clinicaltrials.gov and Web of Science (last search November 2021) for randomized controlled trials. The Cochrane Risk of Bias Tool was used for the included studies, and Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) was used to interpret the certainty of results. Standardized Mean Differences (SMDs) and 95% confidence interval (CI) were calculated for meta-analysis.

RESULTS

Twenty-nine studies were found (1398 people, age range 54-85, 74% are female) and fourteen were included in this review. Intervention duration was divided as short term (immediately after intervention), medium term (<four weeks) and long term (≥ four weeks). Active TENS showed greater improvement in Visual Analogue Scale (VAS) than sham TENS.Combining TENS with other interventions produced superior outcomes compared with other interventions for VAS in all the terms. In the meanwhile, TENS combined with other interventions was superior to other interventions for the pain subgroup of Western Ontario and McMaster Universities Arthritis Index in the medium term and long term. TENS combined with other interventions was superior to other interventions for function in the medium term and long term.

CONCLUSION

TENS could significantly relieve pain, decrease dysfunction and improve walking ability in people with KOA, but it is not effective for stiffness.

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.

Understanding Athletic Trainers' Knowledge, Intervention, and Barriers Toward Arthrogenic Muscle Inhibition

CONTEXT

Arthrogenic muscle inhibition (AMI) is a common neurophysiological response to joint injury. While athletic trainers (ATs) are constantly treating patients with AMI, it is unclear how clinicians are using the available evidence to treat the condition.

OBJECTIVE

To investigate ATs' general knowledge, clinical practice, and barriers for treating AMI.

METHODS

A cross-sectional web-based survey was utilized. The survey was distributed to a random sample of 3000 ATs from the National Athletic Trainers' Association and through social media. 143 board certified ATs (age: 34.6 [10.3] y; experience: 11.7 [9.8] y) from various clinical settings and educational backgrounds were included in the analysis.

RESULTS

One hundred one respondents were able to correctly identify the definition of AMI. The majority of these respondents correctly reported that joint effusion (n = 95, 94.1%) and abnormal activity from joint receptors (n = 91, 90.1%) resulted in AMI. Of the 101 respondents, only 58 (57.4%) reported using disinhibitory interventions to treat AMI. The most frequently used evidence supported interventions were transcutaneous electrical nerve stimulation (n = 38, 65.5%), neuromuscular electrical stimulation (n = 33, 56.9%), and focal joint cooling (n = 25, 43.1%). The interventions used correctly most often based on current evidence were neuromuscular electrical stimulation (n = 29/33, 87.9%) and transcutaneous electrical nerve stimulation (n = 26/38, 68.4%). Overall, difficulty quantifying AMI (n = 62, 61.24%) and lack of education (n = 71, 76.2%) were most frequently perceived as barriers. Respondents that did not use disinhibitory interventions perceived lack of experience treating AMI, understanding the terminology, and access to therapeutic modalities more often than the respondents that reported using disinhibitory interventions.

CONCLUSION

Further education about concepts and treatment about AMI is warranted for ATs. Continued understanding of ATs' clinical practice in regard to AMI may help identify gaps in athletic training clinical education.

Single-Leg Drop Jump Biomechanics After Ankle or Knee Joint Cooling in Healthy Young Adults

CONTEXT

It is unclear if lower-extremity joint cooling alters biomechanics during a functional movement.

OBJECTIVE

To investigate the effects of unilateral lower-extremity cryotherapy on movement alterations during a single-leg drop jump.

DESIGN

A crossover design.

SETTING

Laboratory.

PATIENTS

Twenty healthy subjects (10 males and 10 females; 23 y, 169 cm, 66 kg).

INTERVENTION(S)

Subjects completed a single-leg drop jump before and after a 20-minute ankle or knee joint cooling on the right leg, or control (seated without cooling) on 3 separate days.

MAIN OUTCOME MEASURES

Time to peak knee flexion, vertical ground reaction force, lower-extremity joint angular velocity (sagittal plane only), and angle and moment (sagittal and frontal planes) in the involved leg over the entire ground contact (GC; from initial contact to jump-off) during the first landing. Time to peak knee flexion was compared using an analysis of variance; the rest of the outcome measures were analyzed using functional analyses of variance (P < .05).

RESULTS

Neither joint cooling condition changed the time to peak knee flexion (F2,95 = 0.73, P = .49). Ankle joint cooling reduced vertical ground reaction force (55 N at 4% of GC), knee joint angular velocity (44°/s during 5%-9% of GC), and knee varus moment (181 N·m during 18%-20% of GC). Knee joint cooling resulted in a reduction in knee joint angular velocity (24°/s during 37%-40% of GC) and hip adduction moment (151 N·m during 46%-48% of GC), and an increase in hip joint angular velocity (16°/s during 49%-53% of GC) and plantarflexion angle (1.5° during 11%-29% of GC).

CONCLUSION

Resuming activity immediately after lower-extremity joint cooling does not seem to predispose an individual to injury during landing because altered mechanics are neither overlapping with the injury time period nor of sufficient magnitude to lead to an injury.

Effects of Focal Knee Joint Cooling on Static and Dynamic Strength of the Quadriceps: Innovative Approach to Muscle Conditioning

Recent evidence suggests an innovative approach to muscle conditioning: focal knee joint cooling (FKJC) appears to improve quadriceps function, including static (isometric) strength. However, there is limited evidence on the effects of FKJC on dynamic (concentric and eccentric) strength. Thus, the purpose of the study was to examine dynamic quadriceps strength following FKJC as well as static strength. Twenty-one college-aged participants volunteered. They randomly underwent 20 min of FKJC and control condition at least 72 h apart. FKJC involves two ice bags, placed on the anterior and posterior surfaces of the knee, whereas the control condition received a plastic ice bag filled with candy corn. We assessed isometric and isokinetic (concentric and eccentric) quadriceps strength at two different velocities (60°/s and 180°/s). Participants performed three maximal voluntary contractions for each mode of muscle contraction, before and after each treatment (immediately, 20, and 40 min after). The outcome variable was maximum knee extension peak torque. FKJC did not change peak torque during any mode of muscle contraction (p > 0.05). The current findings suggest that 20 min of FKJC does not change static (isometric) or dynamic (isokinetic) strength of the quadriceps. FKJC was neither beneficial nor harmful to static or dynamic muscular strength.

Shall we use cryotherapy in the treatment in surgical procedures, in acute pain or injury, or in long term pain or dysfunction? - A systematic review

PURPOSE

This review aimed to evaluate the certainty of evidence for the use of cryotherapy in patients with musculoskeletal disorders.

METHODS

PubMed, Embase, Cochrane Library and AMED were searched from January 2000 to January 2018 (update June 2019) for systematic reviews (SRs) and randomized controlled trials (RCTs) reporting outcomes on pain, swelling, range of motion (ROM), function, blood loss, analgesic use, patient satisfaction and adverse advents. The papers were categorised into: surgical procedures, acute pain or injury and long-term pain or dysfunction. Methodological quality and risk of bias were assessed using the AMSTAR and the Swedish Health Technology Assessment instruments. Level of certainty of evidence was synthesized using GRADE.

STUDY SELECTION

Eight SRs and 50 RCTs from a total of 6027 (+839) were included. In total 34 studies evaluated cryotherapy in surgical procedures, twelve evaluated cryotherapy use in acute pain or injury and twelve studies evaluated cryotherapy in long-term pain and dysfunction.

RESULTS

The certainty of evidence is moderate (GRADE III) after surgical procedures to reduce pain, improve ROM, for patient satisfaction and few adverse events are reported. Cryotherapy in acute pain and injury or long-term pain and dysfunction show positive effects but have a higher number of outcomes with low certainty of evidence (GRADE II).

CONCLUSION

Cryotherapy may safely be used in musculoskeletal injuries and dysfunctions. It is well tolerated by patients. More advanced forms of cryotherapy may accentuate the effect. Future research is needed where timing, temperature for cooling, dose (time) and frequency are evaluated.

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.

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.

Electroacupuncture and Manual Acupuncture Increase Joint Flexibility but Reduce Muscle Strength

The objective of this study was to investigate the immediate effects of electroacupuncture and manual acupuncture on hip flexion range of motion (ROM), knee joint (flexion replication at 15° and 45°) and quadriceps (strength and activation) function. Forty-five neurologically healthy adults participated in this randomized controlled laboratory study. Straight leg raise test, modified Thomas test, and hip abductors strength test were performed to determine acupoints. Afterwards, one of three 15-min treatments (control—no treatment, electroacupuncture, or manual acupuncture) was randomly applied using determined acupoints. Measurements (hip flexion ROM, and knee joint and quadriceps function) were recorded at baseline, and at 0, 20, and 40 min post treatment. Both electroacupuncture (4.0°, ES = 0.41) and manual acupuncture (5.4°, ES = 0.95) treatment immediately increased hip flexion ROM, and the increased values persisted for 40-min (p = 0.01). Knee flexion replication (at 15°: p = 0.17; 45°: p = 0.19) and quadriceps activation (p = 0.71) did not change at any of the time points. Post-treatment, both electroacupuncture and manual acupuncture decreased quadriceps strength at 0-min (electroacupuncture: 9.2%, p < 0.0001, ES = 0.60) and 40-min (electroacupuncture: 7.3%, p = 0.005, ES = 0.55; manual acupuncture: 8.7%, p = 0.01, ES = 0.54). A single session of either electroacupuncture or manual acupuncture treatment (selected acupoints based on physical examination) may immediately improve joint flexibility but reduce muscle strength.

A comparison of the effects of electroacupuncture versus transcutaneous electrical nerve stimulation for pain control in knee osteoarthritis: a Bayesian network meta-analysis of randomized controlled trials

BACKGROUND

To compare the effectiveness of electroacupuncture (EA) and transcutaneous electrical nerve stimulation (TENS) for pain control in knee osteoarthritis (KOA).

METHODS

Four English (MEDLINE, EMBASE, Cochrane Library and Web of Science) and three Chinese (China Science Journal Citation Report (VIP), Wanfang and China National Knowledge Infrastructure (CNKI)) language databases were searched for eligible randomized controlled trials (RCTs), comparing four approaches: EA, TENS, medication and sham/placebo controls. The primary outcome was pain intensity, measured by visual analogue scale (VAS), numeric-rating scale (NRS) or Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scale. Classic pairwise and Bayesian network meta-analyses were conducted to integrate the treatment efficacy/effectiveness through direct and indirect evidence.

RESULTS

Thirteen studies were included. In the direct meta-analyses, there was no statistically significant overall effect of EA (mean difference (MD) -4.77, 95% confidence interval (CI) -12.51 to 2.96), while the overall effects of high-frequency transcutaneous electrical nerve stimulation (H-TENS) (MD -16.63, 95% CI -24.57 to -8.69) and medication (MD -7.12, 95% CI -12.07 to -2.17) were statistically significant. In the network meta-analyses, the relative effect of the EA and H-TENS groups (MD 5.07, 95% CI -11.33 to 21.93) on pain control did not differ. Meanwhile, H-TENS demonstrated the highest probability of being the first best treatment, and EA had the second highest probability.

CONCLUSION

The present analysis indicated that both EA and TENS exert significant pain relieving effects in KOA. Among the four treatments, H-TENS was found to be the optimal treatment choice for the management of KOA pain in the short-term, and EA the second best treatment option. Given that the application of TENS is recommended by various international guidelines for the treatment of KOA, EA may also represent a potentially effective non-pharmacologic therapy.

Transcutaneous Electrical Nerve Stimulation Improves Stair Climbing Capacity in People with Knee Osteoarthritis

This study aimed to examine the effect of transcutaneous electrical nerve stimulation (TENS) on stair climbing capacity in individuals with pre-radiographic to mild knee osteoarthritis (OA). This is a secondary analysis of data from a single, participant-blinded, randomized controlled trial with a pre-post design. Participants with pre-radiographic to mild knee OA (mean age, 59.1 years; 72.9% women) were randomly assigned into two groups, a TENS (n = 30) and a sham-TENS groups (n = 29). TENS or sham-TENS treatments were applied to all participants by using the prototype TENS device with pre-specified parameters. The primary outcome measures included valid and reliable functional measures for stair climbing (stair-climb test [SCT]), visual analog scale for knee pain during the SCT, and quadriceps muscle strength. TENS improved SCT time by 0.41 s (95% confidence interval [CI]: 0.07, 0.75). The time reduction in the transition phase explains the TENS therapeutic effect. Post-hoc correlation analyses revealed a non-significant but positive relationship between the pain relief effect and improved 11-step SCT time in the TENS group but not in the sham-TENS group. These results indicate that the TENS intervention may be an option for reducing the burden of early-stage knee OA.

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.

Knee Joint and Quadriceps Dysfunction in Individuals With Anterior Knee Pain, Anterior Cruciate Ligament Reconstruction, and Meniscus Surgery: A Cross-Sectional Study

CONTEXT

While arthrogenous muscle inhibition associated with knee injuries is evident, the relative magnitude of functional deficiency related to each individual knee pathology is unclear.

OBJECTIVE

To compare the knee joint and quadriceps dysfunction among patients with anterior knee pain (AKP) without surgical history and those with surgical history (anterior cruciate ligament reconstruction [ACLR]; meniscus surgery) without current AKP, with matched healthy controls.

DESIGN

Cross-sectional study.

SETTING

Laboratory.

PARTICIPANTS

A total of 66 patients with knee pathologies and 30 controls.

MAIN OUTCOME MEASURES

Pain perception and lower-extremity functional outcomes were assessed. Knee joint function was measured by replication tests. Quadriceps function was measured by strength, voluntary activation, and torque-generating capacity.

RESULTS

Patients with AKP reported greater pain perception compared with the other knee conditions (4.3 vs 0.1 of 10 in Numeric Pain Rating Scale, P < .0001). Compared with the controls: (1) patients with AKP showed a greater error on knee-flexion replications at 75° (2.9° vs 5.4°, P = .002), (2) patients with AKP and ACLR showed less quadriceps strength (AKP: 3.3 vs 2.6 N·m/kg, P = .002; ACLR: 3.3 vs 2.7 N·m/kg, P = .02) and voluntary activation (AKP: 0.982 vs 0.928, P < .0001; ACLR: 0.982 vs 0.946, P = .003), and (3) all knee pathologies reported lower scores on functional outcomes (79 vs 65 of 80 points in Lower-Extremity Functional Scale, P < .0001) and showed less quadriceps torque-generating capacity (10.7 vs 7.8 N·m/s/kg, P < .0001). Among the knee pathologies, patients with AKP showed less quadriceps voluntary activation compared with the patients with meniscus surgery (0.928 vs 0.964, P = .03).

CONCLUSION

As patients with AKP had an additional impairment in knee joint flexion replications and reported a less score in functional outcomes, knee pain may produce a greater impact on functional deficiency.

Simultaneous ice and transcutaneous electrical nerve stimulation decrease anterior knee pain during running but do not affect running kinematics or associated muscle inhibition

BACKGROUND

Runners often experience anterior knee pain and this pain is associated with altered running neuromechanics. The purpose of this study was to examine potential therapeutic benefits (reduced pain and restored running neuromechanics) of simultaneously applied ice and transcutaneous electrical nerve stimulation on experimentally-induced anterior knee pain.

METHODS

Nineteen healthy subjects completed a sham and treatment data collection session. For both sessions, hypertonic saline was infused into the infrapatellar fat pad for approximately 80 min to induce experimental anterior knee pain. Perceived pain levels were measured every two minutes and running neuromechanics were recorded at four time points: pre-pain, pain before treatment, pain immediately post-treatment, and pain 20 min post-treatment.

FINDINGS

The saline infusion significantly increased perceived knee pain from 0 to 2.8 cm. The ice/transcutaneous electrical nerve stimulation treatment significantly reduced perceived knee pain by 35%, six minutes after the treatment initiation. Perceived knee pain remained reduced until eight minutes after the treatment termination. The knee pain significantly decreased peak gluteus medius, vastus lateralis, and vastus medialis activation during running, each by an average of 17% plus/minus 6%; however, none of these decreases were resolved via the therapeutic treatment. Neither the knee pain nor the therapeutic treatment significantly affected peak gluteus maximus activation or peak hip adduction angle.

INTERPRETATION

The experimental pain model effectively produced anterior knee pain and decreased muscle activation during running. The simultaneous ice/transcutaneous electrical nerve stimulation treatment effectively decreased anterior knee pain, but did not restore running neuromechanics that were altered due to the pain.

Best Evidence Rehabilitation for Chronic Pain Part 5: Osteoarthritis

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

Short-term cryotherapy did not substantially reduce pain and had unclear effects on physical function and quality of life in people with knee osteoarthritis: a randomised trial

OBJECTIVE

Does short-term cryotherapy improve pain, function and quality of life in people with knee osteoarthritis (OA)?

DESIGN

Randomised controlled trial with concealed allocation, blinded assessment of some outcomes, and intention-to-treat analysis.

PARTICIPANTS

People living in the community with knee OA.

INTERVENTIONS

The experimental group received cryotherapy, delivered as packs of crushed ice applied to the knee with mild compression. The control group received the same regimen but with sham packs filled with sand. The interventions were applied once a day for 4 consecutive days.

OUTCOME MEASURES

Participants were assessed at baseline and on the day after the 4-day intervention period. The primary outcome was pain intensity according to a visual analogue scale. Secondary outcomes were baseline to post-intervention changes according to the Western Ontario and McMaster Universities Osteoarthritis, Knee injury and Osteoarthritis Outcome; Timed Up and Go test; and 30-Second Chair to Stand test.

RESULTS

Sixty participants were randomised into the experimental group (n = 30) or the control group (n = 30). Twenty-nine participants from each group completed the trial. The mean between-group difference in change in pain severity was -0.8 cm (95% CI -1.6 to 0.1), where negative values favour the experimental group. This result did not reach the nominated smallest worthwhile effect of 1.75 cm. The secondary outcomes had less-precise estimates, with confidence intervals that spanned worthwhile, trivial and mildly harmful effects.

CONCLUSION

Short-term cryotherapy was not superior to a sham intervention in terms of relieving pain or improving function and quality of life in people with knee OA. Although cryotherapy is considered to be a widely used resource in clinical practice, this study does not suggest that it has an important short-term effect, when compared with a sham control, as a non-pharmacological treatment for people with knee osteoarthritis.

REGISTRATION

NCT02725047.

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.

Ankle perturbation generates bilateral alteration of knee muscle onset times after unilateral anterior cruciate ligament reconstruction

BACKGROUND

The aim of this study was to compare muscle activation onset times of knee muscles between the involved and uninvolved knee of patients with unilateral anterior cruciate ligament reconstruction (ACLR), and the uninjured knees of healthy subjects after a controlled perturbation at the ankle level.

METHODS

Fifty male amateur soccer players, 25 with unilateral ACLR using semitendinosus-gracilis graft (age = 28.36 ± 7.87 years; time after surgery = 9 ± 3 months) and 25 uninjured control subjects (age = 24.16 ± 2.67 years) participated in the study. Two destabilizing platforms (one for each limb) generated a controlled perturbation at the ankle of each participant (30°of inversion, 10°plantarflexion simultaneously) in a weight bearing condition. The muscle activation onset times of semitendinosus (ST) and vastus medialis (VM) was detected through an electromyographic (EMG) analysis to assess the neuromuscular function of knee muscles.

RESULTS

Subjects with ACLR had significant delays in EMG onset in the involved (VM = 99.9 ± 30 ms; ST = 101.7 ± 28 ms) and uninvolved knee (VM = 100.4 ± 26 ms; ST = 104.7 ± 28 ms) when compared with the healthy subjects (VM = 69.1 ± 9 ms; ST = 74.6 ± 9 ms). However, no difference was found between involved and uninvolved knee of the ACLR group.

DISCUSSION

The results show a bilateral alteration of knee muscles in EMG onset after a unilateral ACLR, responses that can be elicited with an ankle perturbation. This suggests an alteration in the central processing of proprioceptive information and/or central nervous system re-organization that may affect neuromuscular control of knee muscles in the involved and uninvolved lower limbs.

Immediate effects of transcutaneous electrical nerve stimulation (TENS) administered during resistance exercise on pain intensity and physical performance of healthy subjects: a randomized clinical trial

PURPOSE

Exercise-induced muscle pain is a self-limiting condition which impacts physical activity habits. Transcutaneous electrical nerve stimulation (TENS) promotes pain reduction and functional improvement in different pain conditions. We propose that applying TENS during exercise might reduce pain and improve physical performance. Thus, we aimed to investigate immediate effects of TENS applied during resistance exercise.

METHODS

Healthy subjects of both sexes, irregularly active or sedentary were assigned into two groups: active (n = 24) or placebo (n = 22) TENS. The study was conducted over five moments: on day 0, subjects were recruited, on day 1 subjects performed the one-repetition maximum test (1RM); 72 h later, on day 2, 1RM was retested; 48 h later, on day 3, TENS was applied during a functional-resisted exercise protocol for upper limbs (bench press and rowing), with an intensity of 80% of 1RM; and 24 h after, on day 4, subjects were reevaluated. Assessment included pain intensity at rest and with movement, pressure pain thresholds, and muscle fatigue.

RESULTS

TENS did not reduce pain intensity when compared to placebo (p > 0.05). TENS reduce PPT in the latissmus dorsi: p = 0.02 and anterior tibialis: p = 0.04 in immediate reassessment. Immediate effects of TENS were significant for fatigue perception at rest (p = 0.01) and number of maximum repetitions during exercise sets, starting from the 5th set of rowing exercise (p = 0.002).

CONCLUSION

Our results show that TENS did not reduce pain perception in healthy individuals, but its use induced increased muscle action, contributing to a greater fatigue perception.

Quadriceps Neuromuscular Function in Patients With Anterior Cruciate Ligament Reconstruction With or Without Knee Osteoarthritis: A Cross-Sectional Study

CONTEXT

  Central and peripheral neural adaptations have been identified after anterior cruciate ligament (ACL) injury and reconstruction (ACLR) and are hypothesized to contribute to posttraumatic muscle dysfunction. Limited evidence exists about the temporal nature of neuromuscular adaptations during early and late-term phases of recovery after ACLR, and no researchers have studied patients with posttraumatic osteoarthritis.

OBJECTIVE

  To compare quadriceps neuromuscular function less than 2 years ( early) and more than 2 years ( late) after ACLR, including in patients who experienced posttraumatic knee osteoarthritis.

DESIGN

  Cross-sectional study.

SETTING

  Laboratory.

PATIENTS OR OTHER PARTICIPANTS

  A total of 72 patients after ACLR, consisting of 34 early (9.0 ± 4.3 months postsurgery), 30 late (70.5 ± 41.6 months postsurgery), and 8 with osteoarthritis (115.9 ± 110.0 months postsurgery), and 30 healthy control volunteers.

MAIN OUTCOME MEASURE(S)

  Quadriceps function was measured bilaterally during a single visit to determine normalized Hoffmann reflex (H : M ratio), knee-extension maximal voluntary isometric contraction torque (Nm/kg), central activation ratio (%), fatigue index (% decline), and active motor threshold (%). Comparisons were made using 2-way analyses of variance to identify the effect of limb and group on each outcome measure. We calculated Cohen d effect sizes to assess the magnitude of difference between ACLR and matched control limbs for each group.

RESULTS

  Compared with healthy control limbs, involved-limb maximal voluntary isometric contraction was lower among all patients after ACLR ( P < .001, Cohen d values = -1.00 to -1.75). The central activation ratio ( P < .001, Cohen d = -1.74) and fatigue index ( P = .003, Cohen d = -0.95) were lower among patients only early after ACLR. The active motor threshold was higher among all patients after ACLR ( P < .001, Cohen d values = -0.42 to -1.56).

CONCLUSIONS

  Neuromuscular impairments were present in patients early and late after ACLR, regardless of osteoarthritis status. Quadriceps strength and corticospinal excitability were impaired at each time point compared with values in healthy control individuals, suggesting the need to address cortical function early after ACLR.

Association Between the Single Assessment Numeric Evaluation and the Western Ontario and McMaster Universities Osteoarthritis Index

CONTEXT

  Patient-reported outcomes (PROs) evaluate how patients describe symptoms as well as level of physical function or quality of life. The Western Ontario and McMaster Universities Osteoarthritis (WOMAC) Index is one of the most common PROs used to assess disability in patients with knee osteoarthritis (OA), yet the Single Assessment Numeric Evaluation (SANE) is a single-question instrument that may improve the efficiency associated with the measurement of patient function.

OBJECTIVE

  To determine the associations between (1) SANE_Function and the physical dysfunction subsection of the WOMAC index (WOMAC_Dysfunction) before rehabilitation and after a 4-week therapeutic exercise intervention as well as (2) the percentage change in SANE_Function and WOMAC_Dysfunction in people with knee OA after 4 weeks of therapeutic exercise.

DESIGN

  Cross-sectional study.

SETTING

  Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

  Thirty-six participants (15 men, 21 women) with radiographic knee OA.

INTERVENTION(S)

  Participants completed 12 sessions (over a 4-week period) of therapeutic exercise to strengthen the lower extremity.

MAIN OUTCOME MEASURE(S)

  The SANE_Function and WOMAC_Dysfunction (WOMAC_Dysfunction normalized to 100%) scores were collected before and after the 4-week intervention. Percentage change scores over the 4-week intervention were calculated for both measures.

RESULTS

  Participants with a higher SANE_Function score demonstrated a lower WOMAC_Dysfunction score at baseline (r_s = -0.44, P = .007) and at the 4-week time point (r_s = -0.69, P < .001). There was a nonsignificant and weak association between the changes in the SANE_Function and WOMAC_Dysfunction scores over the 4 weeks of therapeutic exercise (r_s = -0.17, P < .43).

CONCLUSIONS

  The SANE_Function and WOMAC_Dysfunction scores demonstrated moderate to weak associations before and after a 4-week exercise program, respectively, whereas the changes in SANE_Function and WOMAC_Dysfunction scores were not associated. These PROs may be measuring different aspects of self-reported function and therefore should not be used interchangeably to determine a therapeutic response.

Unilateral Quadriceps Strengthening With Disinhibitory Cryotherapy and Quadriceps Symmetry After Anterior Cruciate Ligament Reconstruction

CONTEXT

  The effect of unilateral cryotherapy-facilitated rehabilitation exercise on involved-limb quadriceps function and limb symmetry in individuals with quadriceps dysfunction after anterior cruciate ligament reconstruction (ACLR) remains unclear.

OBJECTIVE

  To measure the effect of a 2-week unilateral cryotherapy-facilitated quadriceps-strengthening program on knee-extension strength and quadriceps central activation ratio (CAR) in participants with ACLR.

DESIGN

  Controlled laboratory study.

SETTING

  Laboratory.

PATIENTS OR OTHER PARTICIPANTS

  A total of 10 volunteers with unilateral ACLR (1 man, 9 women; age = 21.0 ± 2.8 years, height = 164.6 ± 5.0 cm, mass = 64.0 ± 6.1 kg, body mass index = 23.7 ± 2.7 kg/m²) and 10 healthy volunteers serving as control participants (1 man, 9 women; age = 20.8 ± 2.5 years, height = 169.1 ± 6.2 cm, mass = 61.1 ± 6.4 kg, body mass index = 21.4 ± 2.3 kg/m²) participated.

INTERVENTION(S)

  Participants with ACLR completed a 2-week unilateral cryotherapy-facilitated quadriceps-strengthening intervention.

MAIN OUTCOME MEASURE(S)

  Bilateral normalized knee-extension maximal voluntary isometric contraction (MVIC) torque (Nm/kg) and quadriceps CAR (%) were assessed preintervention and postintervention. Limb symmetry index (LSI) was calculated at preintervention and postintervention testing. Preintervention between-groups differences in unilateral quadriceps function and LSI were evaluated using independent-samples t tests. Preintervention-to-postintervention differences in quadriceps function were evaluated using paired-samples t tests. Cohen d effect sizes (95% confidence interval [CI]) were calculated for each comparison.

RESULTS

  Preintervention between-groups comparisons revealed less knee-extension MVIC torque and quadriceps CAR for the ACLR limb (MVIC: P = .01, Cohen d = -1.31 [95% CI = -2.28, -0.34]; CAR: P = .004, Cohen d = -1.48 [95% CI = -2.47, -0.49]) and uninvolved limb (MVIC: P = .03, Cohen d = -1.05 [95% CI = -1.99, -0.11]; CAR: P = .01, Cohen d = -1.27 [95% CI = -2.23, -0.31]) but not for the LSI (MVIC: P = .46, Cohen d = -0.34 [95% CI = -1.22, 0.54]; CAR: P = .60, Cohen d = 0.24 [95% CI = -0.64, 1.12]). In the ACLR group, participants had improved knee-extension MVIC torque in the involved limb ( P = .04, Cohen d = 0.32 [95% CI = -0.56, 1.20]) and uninvolved limb ( P = .03, Cohen d = 0.29 [95% CI = -0.59, 1.17]); however, the improvement in quadriceps CAR was limited to the involved limb ( P = .02, Cohen d = 1.16 [95% CI = 0.21, 2.11]). We observed no change in the LSI with the intervention for knee-extension MVIC torque ( P = .74, Cohen d = 0.09 [95% CI = -0.79, 0.97]) or quadriceps CAR ( P = .61, Cohen d = 0.26 [95% CI = -0.62, 1.14]).

CONCLUSIONS

  Two weeks of cryotherapy-facilitated exercise may improve involved-limb quadriceps function while preserving between-limbs symmetry in patients with a history of ACLR.

Phisical modalities on the functional performance in knee osteoarthritis: a sytematic review

Abstract Introduction: Despite recent advances in the treatment of osteoarthritis (OA), few studies have evaluated the longitudinal effect of physical modalities in functional capacity in patients with knee OA. Thereby, since the physical components and pain can affect the functional performance of daily activities, the effect of these treatment’s form is still to be established. Objective: Evaluate the effectiveness of therapeutic ultrasound, electrical stimulation and phototherapy in the functional performance, in patients with knee osteoarthritis. Methods: Articles present in the PubMed, Lilacs, SciELO and PEDro’s databases were evaluated. The used keywords were “pulsed ultrasound therapy”, “ultrasound therapy”, “electric stimulation” and “low level laser therapy” in combination with “knee osteoarthritis”. Were included in this presented review, randomized clinical studies using ultrasound, electrical and laser stimulation in subjects with knee osteoarthritis. To evaluate the methodological quality of the selected studies, was used the PEDro’s scale. The dependent variables of the study were: pain, physical function, joint stiffness, life quality and functional performance. Results: 268 studies were found, of these, 41 studies met eligibility criteria and were classified for analysis in full. The used methodology in the studies varied widely, however, in most cases there was improvement in functional performance of individuals with knee OA, with the use of physical modalities, for the pulsed ultrasound, continuous ultrasound, electrical stimulation and laser resourses. Conclusion: The physical modalities used in the studies demonstrated improvement in functional performance of individuals with knee OA.

Performance on a Clinical Quadriceps Activation Battery Is Related to a Laboratory Measure of Activation and Recovery After Total Knee Arthroplasty

OBJECTIVE

To determine the relation between performance on a clinical quadriceps activation battery with (1) activation measured by doublet interpolation and (2) recovery of quadriceps strength and functional performance after total knee arthroplasty (TKA).

DESIGN

Planned secondary analysis of a randomized controlled trial.

SETTING

University research laboratory.

PARTICIPANTS

Patients (N=162; mean age, 63±7y; 89 women) undergoing TKA.

MAIN OUTCOME MEASURES

Patients were classified as high (quadriceps activation battery ≥4/6) or low (quadriceps activation battery ≤3/6) based on performance on the quadriceps activation battery measured 4 days after TKA. Differences between groups in activation and recovery at 1, 2, 3, 6, and 12 months after TKA were compared using a repeated-measures maximum likelihood model.

RESULTS

The low quadriceps activation battery group demonstrated poorer quadriceps activation via doublet interpolation (P=.01), greater quadriceps strength loss (P=.01), and greater functional performance decline (all P<.001) at 1 month after TKA compared with the high quadriceps activation battery group. Differences between low and high quadriceps activation battery groups on all measures did not persist at 3 and 12 months (all P>.05).

CONCLUSIONS

Poor performance on the quadriceps activation battery early after TKA is related to poor quadriceps activation and poor recovery in the early postoperative period. Patients in the low quadriceps activation battery group took 3 months to recover to the same level as the high quadriceps activation battery group. The quadriceps activation battery may be useful in identifying individuals who need specific interventions to target activation deficits or different care pathways in the early postoperative period to speed recovery after TKA.

Acute Responses of Strength and Running Mechanics to Increasing and Decreasing Pain in Patients With Patellofemoral Pain

CONTEXT

  Patellofemoral pain (PFP) is typically exacerbated by repetitive activities that load the patellofemoral joint, such as running. Understanding the mediating effects of changes in pain in individuals with PFP might inform injury progression, rehabilitation, or both.

OBJECTIVE

  To investigate the effects of changing pain on muscular strength and running biomechanics in those with PFP.

DESIGN

  Crossover study.

SETTING

  University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

  Seventeen participants (10 men, 7 women) with PFP.

INTERVENTION(S)

  Each participant completed knee pain-reducing and pain-inducing protocols in random order. The pain-reducing protocol consisted of 15 minutes of transcutaneous electric nerve stimulation (TENS) around the patella. The pain-inducing protocol was sets of 20 repeated single-legged squats (RSLS). Participants completed RSLS sets until either their pain was within at least 1 cm of their pain during an exhaustive run or they reached 10 sets.

MAIN OUTCOME MEASURE(S)

  Pain, isometric hip and trunk strength, and running mechanics were assessed before and after the protocols. Dependent variables were pain, normalized strength (abduction, extension, external rotation, lateral trunk flexion), and peak lower extremity kinematics and kinetics in all planes. Pain scores were analyzed using a Friedman test. Strength and mechanical variables were analyzed using repeated-measures analyses of variance. The α level was set at P < .05.

RESULTS

  Pain was decreased after the TENS (pretest: 3.10 ± 1.95, posttest: 1.89 ± 2.33) and increased after the RSLS (baseline: 3.10 ± 1.95, posttest: 4.38 ± 2.40) protocols (each P < .05). The RSLS protocol resulted in a decrease in hip-extension strength (baseline: 0.355 ± 0.08 kg/kg, posttest: 0.309 ± 0.09 kg/kg; P < .001). Peak plantar-flexion angle was decreased after RSLS (baseline: -13.97° ± 6.41°, posttest: -12.84° ± 6.45°; P = .003). Peak hip-extension (pretest: -2.31 ± 0.46) and hip-abduction (pretest: -2.02 ± 0.35) moments decreased after both the TENS (extension: -2.15 ± 0.48 Nm/kg, P = .015; abduction: -1.91 ± 0.33 Nm/kg, P = .015) and RSLS (extension: -2.18 ± 0.52 Nm/kg, P = .003; abduction: -1.87 ± 0.36 Nm/kg, P = .039) protocols.

CONCLUSIONS

  This study presents a novel and effective method of increasing pain in persons with PFP. Functionally increased pain after RSLS coincides with reduced hip-extensor muscle strength and decreased plantar-flexion angle during running. The TENS treatment decreased pain during running in those with PFP but failed to influence strength. Hip moments were reduced by both protocols, which may demonstrate that acute increases or decreases in pain cause runners to change their mechanics.

No Influence of Transcutaneous Electrical Nerve Stimulation on Exercise-Induced Pain and 5-Km Cycling Time-Trial Performance

Introduction: Afferent information from exercising muscle contributes to the sensation of exercise-induced muscle pain. Transcutaneous electrical nerve stimulation (TENS) delivers low–voltage electrical currents to the skin, inhibiting nociceptive afferent information. The use of TENS in reducing perceptions of exercise-induced pain has not yet been fully explored. This study aimed to investigate the effect of TENS on exercise-induced muscle pain, pacing strategy, and performance during a 5-km cycling time trial (TT).

Methods: On three separate occasions, in a single-blind, randomized, and cross-over design, 13 recreationally active participants underwent a 30-min TENS protocol, before performing a 5-km cycling TT. TENS was applied to the quadriceps prior to exercise under the following conditions; control (CONT), placebo with sham TENS application (PLAC), and an experimental condition with TENS application (TENS). Quadriceps fatigue was assessed with magnetic femoral nerve stimulation assessing changes in potentiated quadriceps twitch force at baseline, pre and post exercise. Subjective scores of exertion, affect and pain were taken every 1-km.

Results: During TTs, application of TENS did not influence pain perceptions (P = 0.68, ηp2 = 0.03). There was no significant change in mean power (P = 0.16, ηp2 = 0.16) or TT duration (P = 0.17, ηp2 = 0.14), although effect sizes were large for these two variables. Changes in power output were not significant but showed moderate effect sizes at 500-m (ηp2 = 0.10) and 750-m (ηp2 = 0.10). Muscle recruitment as inferred by electromyography data was not significant, but showed large effect sizes at 250-m (ηp2 = 0.16), 500-m (ηp2 = 0.15), and 750-m (ηp2 = 0.14). This indicates a possible effect for TENS influencing performance up to 1-km.

Discussion: These findings do not support the use of TENS to improve 5-km TT performance.

Acupuncture for chronic pain and depression in primary care: a programme of research

Background

There has been an increase in the utilisation of acupuncture in recent years, yet the evidence base is insufficiently well established to be certain about its clinical effectiveness and cost-effectiveness. Addressing the questions related to the evidence base will reduce uncertainty and help policy- and decision-makers with regard to whether or not wider access is appropriate and provides value for money.

Aim

Our aim was to establish the most reliable evidence on the clinical effectiveness and cost-effectiveness of acupuncture for chronic pain by drawing on relevant evidence, including recent high-quality trials, and to develop fresh evidence on acupuncture for depression. To extend the evidence base we synthesised the results of published trials using robust systematic review methodology and conducted a randomised controlled trial (RCT) of acupuncture for depression.

Methods and results

We synthesised the evidence from high-quality trials of acupuncture for chronic pain, consisting of musculoskeletal pain related to the neck and low back, osteoarthritis of the knee, and headache and migraine, involving nearly 18,000 patients. In an individual patient data (IPD) pairwise meta-analysis, acupuncture was significantly better than both sham acupuncture (p < 0.001) and usual care (p < 0.001) for all conditions. Using network meta-analyses, we compared acupuncture with other physical therapies for osteoarthritis of the knee. In both an analysis of all available evidence and an analysis of a subset of better-quality trials, using aggregate-level data, we found acupuncture to be one of the more effective therapies. We developed new Bayesian methods for analysing multiple individual patient-level data sets to evaluate heterogeneous continuous outcomes. An accompanying cost-effectiveness analysis found transcutaneous electrical nerve stimulation (TENS) to be cost-effective for osteoarthritis at a threshold of £20,000 per quality-adjusted life-year when all trials were synthesised. When the analysis was restricted to trials of higher quality with adequate allocation concealment, acupuncture was cost-effective. In a RCT of acupuncture or counselling compared with usual care for depression, in which half the patients were also experiencing comorbid pain, we found acupuncture and counselling to be clinically effective and acupuncture to be cost-effective. For patients in whom acupuncture is inappropriate or unavailable, counselling is cost-effective.

Conclusion

We have provided the most robust evidence from high-quality trials on acupuncture for chronic pain. The synthesis of high-quality IPD found that acupuncture was more effective than both usual care and sham acupuncture. Acupuncture is one of the more clinically effective physical therapies for osteoarthritis and is also cost-effective if only high-quality trials are analysed. When all trials are analysed, TENS is cost-effective. Promising clinical and economic evidence on acupuncture for depression needs to be extended to other contexts and settings. For the conditions we have investigated, the drawing together of evidence on acupuncture from this programme of research has substantially reduced levels of uncertainty. We have identified directions for further research. Our research also provides a valuable basis for considering the potential role of acupuncture as a referral option in health care and enabling providers and policy-makers to make decisions based on robust sources of evidence.

Trial registration

Current Controlled Trials ISRCTN63787732.

Funding

The National Institute for Health Research Programme Grants for Applied Research programme.

The immediate effect of patellar tendon strap on weight-bearing asymmetry during squatting in patients with unilateral knee osteoarthritis: A pilot study

BACKGROUND

Knee osteoarthritis has commonly been associated with a symptom of pain resulting in an inter-limb weight-bearing asymmetry during functional tasks. Patellar tendon strap is one of the non-pharmacologic interventions to alleviate knee pain.

OBJECTIVES

To investigate the immediate effect of a patellar tendon strap on weight-bearing asymmetry during squatting in people with unilateral knee osteoarthritis.

STUDY DESIGN

Cross-sectional study.

METHODS

Ten patients with unilateral knee osteoarthritis and 10 healthy subjects were included in the study. Weight-bearing asymmetry of patients was assessed using a weight-bearing squat test during squatting at 30° and 60° both with and without patellar tendon strap. Pain intensity was assessed during squatting in unstrapped and strapped conditions with Visual Analog Scale.

RESULTS

The decrease in weight-bearing asymmetry values immediately after wearing patellar tendon strap during 30° (p = 0.006) and 60° (p = 0.011) of squatting tests was significantly higher in knee osteoarthritis patients than in healthy subjects. Reported pain intensity was similar in unstrapped and strapped conditions (p = 0.066).

CONCLUSION

The results of this study showed improved inter-limb weight-bearing symmetry during squatting. Further research with larger sample sizes investigating the effect of patellar tendon strap on weight-bearing asymmetry during functional activities in people with knee osteoarthritis is warranted.

CLINICAL RELEVANCE

Patellar tendon straps (easily fit and cheap unlike knee braces) had more improvements in inter-limb weight-bearing symmetry during squatting in people with knee osteoarthritis compared to healthy subjects. This study is a new insight for future studies to investigate clinical benefits of wearing patellar tendon straps in this population.

Effects of Kinesio taping in patients with quadriceps inhibition: A randomized, single-blinded study

OBJECTIVE

To determine effects of Kinesio taping (KT) on quadriceps activation and maximal voluntary isometric contraction (MVIC) in patients with quadriceps inhibition.

DESIGN

Randomized, single-blinded.

SETTING

Laboratory.

PATIENTS

Sixteen participants (9 males, 7 females) with quadriceps inhibition, as determined by 90% or lower in central activation ratio (CAR), participated.

MAIN OUTCOME MEASURES

Hoffmann reflex (H-reflex) of the vastus medialis and quadriceps CAR and MVIC were measured before taping, and participants were randomly allocated to either KT (KT application with tension) or sham (non-elastic tape application without tension) group. H-reflexes were assessed immediately and 20 min after tape was applied over the rectus femoris. All outcomes were measured again after tape was removed when participants returned the laboratory 24-48 h after taping.

RESULTS

Two-way repeated ANOVA found no group-by-time interaction for: H-reflex (F_3,42 = 1.94, P = 0.14), CAR (F_1,14 = 0.03, P = 0.86), or MVIC (F_1,14 = 0.007, P = 0.93). None of the outcome measures differed between groups or over time (P > 0.05).

CONCLUSIONS

KT applied to the rectus femoris did not change H-reflex of the vastus medialis and quadriceps CAR and MVIC in patients with quadriceps inhibition.

Impact of quadriceps strengthening on response to fatiguing exercise following ACL reconstruction

OBJECTIVES

Patients commonly experience altered response to fatiguing exercise after ACL reconstruction (ACLR). The objective of this study was to assess the impact of quadriceps strengthening on response to exercise after ACLR.

DESIGN

Clinical trial.

METHODS

Ten participants with a history of primary, unilateral ACLR (sex=9F/1M, age=21.0±2.8 years, BMI=23.7±2.7kg/m²) and 10 healthy participants (sex=9F/1M, age=22.2±3.2 years, BMI=23.8±3.9kg/m²) participated. ACLR participants completed a 2-week quadriceps strengthening intervention including 14 progressive strengthening exercise sessions. Normalized knee extension maximum voluntary isometric contraction (MVIC) torque (Nm/kg) and quadriceps central activation ratio (%, CAR) were measured before and after a 30-minute fatiguing exercise protocol. ACLR participants completed testing before and after the 2-week intervention while control participants completed a single testing session.

RESULTS

The intervention significantly improved normalized knee extension MVIC torque (pre-intervention=1.85±0.67Nm/kg, post-intervention=2.09±0.81Nm/kg, p=0.04) and quadriceps CAR in the ACLR involved limb (pre-intervention=86.51±5.03%, post-intervention=92.94±5.99%, p=0.02). Quadriceps CAR (pre-intervention=1.13±9.04%, post-intervention=-3.97±4.59%, p=0.16) and normalized knee extension MVIC torque (pre-intervention=0.26±20.90%, post-intervention=-8.02±12.82%, p=0.30) response to exercise did not significantly change from pre-intervention to post-intervention conditions.

CONCLUSIONS

Two weeks of quadriceps strengthening reduced this between group difference in the involved limb which may indicate restoration of more optimal quadriceps neuromuscular function and increased demand on the quadriceps during physical activity.

Rehabilitation Strategies for the Athletic Individual with Early Knee Osteoarthritis

Knee osteoarthritis (OA) is a major cause of disability in the United States. The condition has most commonly been associated with elderly sedentary individuals; however, it also can affect those who participate in regular athletic activities. The diagnosis and management of these individuals can be challenging because of both their higher level of physical activity and their overall athletic goals. Treatment requires an appropriate exercise regimen, rehabilitation program, and education of both the athlete and the coach. The focus of our article is to provide an up-to-date overview of the evaluation and management of the athletic individual who presents with symptomatic early knee OA, in particular, the nonsurgical rehabilitation treatment options available to the practitioner and the evidence to support these recommendations.

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.

The effects of joint aspiration and intra-articular corticosteroid injection on flexion reflex excitability, quadriceps strength and pain in individuals with knee synovitis: a prospective observational study

Introduction

Substantial weakness of the quadriceps muscles is typically observed in patients with arthritis. This is partly due to ongoing neural inhibition that prevents the quadriceps from being fully activated. Evidence from animal studies suggests enhanced flexion reflex excitability may contribute to this weakness. This prospective observational study examined the effects of joint aspiration and intra-articular corticosteroid injection on flexion reflex excitability, quadriceps muscle strength and knee pain in individuals with knee synovitis.

Methods

Sixteen patients with chronic arthritis and clinically active synovitis of the knee participated in this study. Knee pain flexion reflex threshold, and quadriceps peak torque were measured at baseline, immediately after knee joint aspiration alone and 5 ± 2 and 15 ± 2 days after knee joint aspiration and the injection of 40 mg of methylprednisolone acetate.

Results

Compared to baseline, knee pain was significantly reduced 5 (p = 0.001) and 15 days (p = 0.009) post intervention. Flexion reflex threshold increased immediately after joint aspiration (p = 0.009) and 5 (p = 0.01) and 15 days (p = 0.002) post intervention. Quadriceps peak torque increased immediately after joint aspiration (p = 0.004) and 5 (p = 0.001) and 15 days (p <0.001) post intervention.

Conclusions

The findings from this study suggest that altered sensory output from an inflamed joint may increase flexion reflex excitability in humans, as has previously been shown in animals. Joint aspiration and corticosteroid injection may be a clinically useful intervention to reverse quadriceps muscle weakness in individuals with knee synovitis.

Quadriceps muscle function after rehabilitation with cryotherapy in patients with anterior cruciate ligament reconstruction

CONTEXT

Persistent muscle weakness after anterior cruciate ligament (ACL) reconstruction may be due to underlying activation failure and arthrogenic muscle inhibition (AMI). Knee-joint cryotherapy has been shown to improve quadriceps function transiently in those with AMI, thereby providing an opportunity to improve quadriceps muscle activation and strength in patients with a reconstructed ACL.

OBJECTIVE

To compare quadriceps muscle function in patients with a reconstructed ACL who completed a 2-week intervention including daily cryotherapy (ice bag), daily exercises, or both.

DESIGN

Cross-sectional study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 30 patients with reconstructed ACLs who were at least 6 months post-index surgery and had measurable quadriceps AMI.

INTERVENTION(S)

The patients attended 4 supervised visits over a 2-week period. They were randomly assigned to receive 20 minutes of knee-joint cryotherapy, 1 hour of therapeutic rehabilitation exercises, or cryotherapy followed by exercises.

MAIN OUTCOME MEASURE(S)

We measured quadriceps Hoffmann reflex, normalized maximal voluntary isometric contraction torque, central activation ratio using the superimposed-burst technique, and patient-reported outcomes before and after the intervention period.

RESULTS

After the 2-week intervention period, patients who performed rehabilitation exercises immediately after cryotherapy had higher normalized maximal voluntary isometric contraction torques (P = .002, Cohen d effect size = 1.4) compared with those who received cryotherapy alone (P = .16, d = 0.58) or performed exercise alone (P = .16, d = 0.30).

CONCLUSIONS

After ACL reconstruction, patients with AMI who performed rehabilitation exercises immediately after cryotherapy experienced greater strength gains than those who performed cryotherapy or exercises alone.

The Time Course of Knee Swelling Post Total Knee Arthroplasty and Its Associations with Quadriceps Strength and Gait Speed

This study examines the time course of knee swelling post total knee arthroplasty (TKA) and its associations with quadriceps strength and gait speed. Eighty-five patients with unilateral TKA participated. Preoperatively and on post-operative days (PODs) 1, 4, 14, and 90, knee swelling was measured using bioimpedance spectrometry. Preoperatively and on PODs 14 and 90, quadriceps strength was measured using isokinetic dynamometry while fast gait speed was measured using the timed 10-meter walk. On POD1, knee swelling increased ~35% from preoperative levels after which, knee swelling reduced but remained at ~11% above preoperative levels on POD90. In longitudinal, multivariable analyses, knee swelling was associated with quadriceps weakness (P<0.01) and slower gait speed (P=0.03). Interventions to reduce post-TKA knee swelling may be indicated to improve quadriceps strength and gait speed.

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.