Changes in soleus motoneuron pool excitability after artificial knee joint effusion

Individuals With Chronic Ankle Instability Show Abnormalities in Maximal and Submaximal Isometric Strength of the Knee Extensor and Flexor Muscles

BACKGROUND

It has been shown that chronic ankle instability (CAI) leads to abnormalities in neuromuscular control of more proximal joints than the ankle. Although strength of the hip and the ankle muscles has been largely investigated providing concordant results, limited evidence with contrasting results has been reported regarding knee extensor and flexor muscles.

PURPOSE

To investigate maximal and submaximal isometric muscle strength in individuals with CAI.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fifteen participants with unilateral CAI and 15 healthy matched controls were recruited. To quantify maximal strength, peak forces were recorded during a maximal isometric voluntary contraction of knee extensor and flexor muscles at 30° and 90° of knee flexion and normalized by the body weight of each participant. At both angles, submaximal isometric contractions at 20%, 50%, and 80% of the maximal voluntary isometric contraction were performed to analyze strength steadiness, in terms of coefficient of variation, and strength accuracy, in terms of absolute error. During all the assessments, knee extensor and flexor muscle activation was recorded by means of surface electromyography.

RESULTS

Knee flexor maximal isometric strength was significantly lower in the injured limb of individuals with CAI in comparison with healthy controls at both 30° (0.15 ± 0.05 vs 0.20 ± 0.05; P < .05) and 90° (0.14 ± 0.04 vs 0.18 ± 0.05; P < .05). Knee extensor and flexor steadiness was significantly lower (higher coefficient of variation) in both the injured and the noninjured limbs of individuals with CAI in comparison with healthy individuals at 90° and at 30° for knee flexor steadiness of the injured limb. Knee extensor and flexor accuracy was lower (higher absolute error) in both the injured and noninjured limbs of individuals with CAI in comparison with healthy individuals, mainly at 30°, while at 90° it was lower only in the injured limb. No differences between the 2 groups were found for maximal isometric strength of knee extensor muscles, as well as for muscle activations.

CONCLUSION

Individuals with CAI show abnormalities in maximal and submaximal isometric strength of knee flexor muscles, and submaximal strength of the knee extensor muscles. Further studies should deeply investigate mechanisms leading to these abnormalities.

CLINICAL RELEVANCE

Rehabilitation interventions should consider abnormalities of neuromuscular control affecting joints more proximal than the ankle in individuals with CAI.

REGISTRATION

NCT05273177 (ClinicalTrials.gov identifier).

Postural Assessment Systems in the Prevention of Haemophilic Arthropathy: A Narrative Review

This narrative review aims to give an overview of some postural evaluation systems currently used in patients with haemophilia. Among them, first, we analyse the HJHS scale, recognized as a specific evaluation tool for haemophilic arthropathy. Second, we focus on other systems usually used in non-haemophilic patients that have also shown good applicability in this patient category, such as gait analysis, stabilometry, and baropodometric examination. This review underlines the use these tools could have in clinical practice to identify the early postural alterations in patients with haemophilia and set up personalised rehabilitation programs.

Effects of combined whole body vibration and resistance training on lower quadrants electromyographic activity, muscle strength and power in athletes

BACKGROUND

Whole body vibration (WBV) with resistance training is one of the increasing ways of gaining ankle and foot complex muscle strength and power for the rehabilitative and prophylactic purpose in athletes.

OBJECTIVE

The purpose of the study was to compare the effects of combined WBV and resistance training (RVE) with strength training alone (RE) on alteration of gastrocnemius lateralis and vastus medialis obliquus muscle activity and strength, and power performance in athletes.

METHODS

The study was performed on 23 university-level male athletes who were randomized into two groups as RVE (n = 12; age 22.2 ± 1.94 years) and RE (n = 11; age 21.60 ± 1.78 years). The training program was scheduled three times per week for six weeks (18 sessions). Gastrocnemius lateralis (GL) and vastus medialis obliquus (VMO) were measured for muscle activity and isometric strength with surface EMG device and handheld dynamometer respectively. Counter-movement jump (CMJ) was used for measuring power. All the participants were assessed for outcome measures at baseline and then after 6 weeks. Group (RVE vs. RE) by time (pre vs. post) effects were compared through a 2-way interaction utilizing mixed model repeated measure ANOVA.

RESULTS

After training, VMO muscle activity (group effects) increased significantly in the RVE group (p < 0.05). However, both the groups showed statistically significant time and group × time interaction effects for muscle activity of VMO, isometric strength (VMO and GL), and CMJ (p < 0.05).

CONCLUSION

WBV might serve as an adjunct modality for enhancement of the neuromuscular activity of the VMO muscle. However, RVE had no additive effect when compared to RE alone on muscle strength and power in athletes. The long-term impacts of combined WBV and resistance training on other foot and ankles muscle should be investigated in future studies.

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

BACKGROUND

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

OBJECTIVE

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

DESIGN

Systematic review with meta-analyses.

DATA SOURCES

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

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

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

RESULTS

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

CONCLUSIONS

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

TRIAL REGISTRATION NUMBER

PROSPERO CRD42019141850.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

TRIAL REGISTRATION

Registered through PROSPERO CRD42020158714.

Greater magnitude tibiofemoral contact forces are associated with reduced prevalence of osteochondral pathologies 2-3 years following anterior cruciate ligament reconstruction

PURPOSE

External loading of osteoarthritic and healthy knees correlates with current and future osteochondral tissue state. These relationships have not been examined following anterior cruciate ligament reconstruction. We hypothesised greater magnitude tibiofemoral contact forces were related to increased prevalence of osteochondral pathologies, and these relationships were exacerbated by concomitant meniscal injury.

METHODS

This was a cross-sectional study of 100 individuals (29.7 ± 6.5 years, 78.1 ± 14.4 kg) examined 2-3 years following hamstring tendon anterior cruciate ligament reconstruction. Thirty-eight participants had concurrent meniscal pathology (30.6 ± 6.6 years, 83.3 ± 14.3 kg), which included treated and untreated meniscal injury, and 62 participants (29.8 ± 6.4 years, 74.9 ± 13.3 kg) were free of meniscal pathology. Magnetic resonance imaging of reconstructed knees was used to assess prevalence of tibiofemoral osteochondral pathologies (i.e., cartilage defects and bone marrow lesions). A calibrated electromyogram-driven neuromusculoskeletal model was used to predict medial and lateral tibiofemoral compartment contact forces from gait analysis data. Relationships between contact forces and osteochondral pathology prevalence were assessed using logistic regression models.

RESULTS

In patients with reconstructed knees free from meniscal pathology, greater medial contact forces were related to reduced prevalence of medial cartilage defects (odds ratio (OR) = 0.7, Wald χ²(2) = 7.9, 95% confidence interval (CI) = 0.50-95, p = 0.02) and medial bone marrow lesions (OR = 0.8, Wald χ²(2) = 4.2, 95% CI = 0.7-0.99, p = 0.04). No significant relationships were found in lateral compartments. In reconstructed knees with concurrent meniscal pathology, no relationships were found between contact forces and osteochondral pathologies.

CONCLUSIONS

In patients with reconstructed knees free from meniscal pathology, increased contact forces were associated with fewer cartilage defects and bone marrow lesions in medial, but not, lateral tibiofemoral compartments. No significant relationships were found between contact forces and osteochondral pathologies in reconstructed knees with meniscal pathology for any tibiofemoral compartment. Future studies should focus on determining longitudinal effects of contact forces and changes in osteochondral pathologies.

LEVEL OF EVIDENCE

IV.

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.

Osteoarthritis year in review 2016: mechanics

Inappropriate biomechanics, namely wear-and-tear, has been long believed to be a main cause of osteoarthritis (OA). However, this view is now being re-evaluated, especially when examined alongside mechanobiology and new biomechanical studies. These are multiscale experimental and computational studies focussing on cell- and tissue-level mechanobiology through to organ- and whole-body-level biomechanics, which focuses on the biomechanical and biochemical environment of the joint tissues. This review examined papers from April 2015 to April 2016, with a focus on multiscale experimental and computational biomechanical studies of OA. Assessing the onset or progression of OA at organ- and whole-body-levels, gait analysis, medical imaging and neuromusculoskeletal modelling revealed the extent to which tissue damage changes the view of inappropriate biomechanics. Traditional gait analyses studies reported that conservative treatments can alter joint biomechanics, thereby improving pain and function experienced by those with OA. Results of animal models of OA were consistent with these human studies, showing interactions among bone, cartilage and meniscus biomechanics and the onset and/or progression OA. Going down size scales, experimental and computational studies probed the nanosize biomechanics of molecules, cells and extracellular matrix, and demonstrated how the interactions between biomechanics and morphology affect cartilage dynamic poroelastic behaviour and pathways to OA. Finally, integration of multiscale experimental data and computational models were proposed to predict cartilage extracellular matrix remodelling and the development of OA. Summarising, experimental and computational methods provided a nuanced biomechanical understanding of the sub-cellular, cellular, tissue, organ and whole-body mechanisms involved in OA.

Tibiofemoral contact forces during walking, running and sidestepping

We explored the tibiofemoral contact forces and the relative contributions of muscles and external loads to those contact forces during various gait tasks. Second, we assessed the relationships between external gait measures and contact forces. A calibrated electromyography-driven neuromusculoskeletal model estimated the tibiofemoral contact forces during walking (1.44±0.22ms(-1)), running (4.38±0.42ms(-1)) and sidestepping (3.58±0.50ms(-1)) in healthy adults (n=60, 27.3±5.4years, 1.75±0.11m, and 69.8±14.0kg). Contact forces increased from walking (∼1-2.8 BW) to running (∼3-8 BW), sidestepping had largest maximum total (8.47±1.57 BW) and lateral contact forces (4.3±1.05 BW), while running had largest maximum medial contact forces (5.1±0.95 BW). Relative muscle contributions increased across gait tasks (up to 80-90% of medial contact forces), and peaked during running for lateral contact forces (∼90%). Knee adduction moment (KAM) had weak relationships with tibiofemoral contact forces (all R(2)<0.36) and the relationships were gait task-specific. Step-wise regression of multiple external gait measures strengthened relationships (0.20<Radj(2)<0.78), but were variable across gait tasks. Step-wise regression equations from a particular gait task (e.g. walking) produced large errors when applied to a different gait task (e.g. running or sidestepping). Muscles well stabilized the knee, increasing their role in stabilization from walking to running to sidestepping. KAM was a poor predictor of medial contact force and load distributions. Step-wise regression models results suggest the relationships between external gait measures and contact forces cannot be generalized across tasks. Neuromusculoskeletal modelling may be required to examine tibiofemoral contact forces and role of muscle in knee stabilization across gait tasks.

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.

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

BACKGROUND

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

METHODS

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

FINDINGS

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

INTERPRETATION

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

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.

Avaliação funcional do joelho em portadores da síndrome da dor femoropatelar (SDFP): comparação entre as escalas KOS e IKDC

OBJETIVO: Muitos instrumentos têm sido propostos para avaliar o joelho, tornando muitas vezes difícil a sua escolha. Entre esses instrumentos destacam-se as escalas Knee Injury and Osteoarthritis Outcome Score (KOS) e International Knee Documentation Committee (IKDC), mas ainda não é claro qual delas seria melhor para avaliar o joelho de portadores da síndrome da dor femoropatelar (SDFP). O objetivo deste estudo foi comparar as escalas de avaliação KOS e IKDC para verificar qual delas seria mais apropriada na identificação de acometimento nos portadores da SDFP. MÉTODOS: O estudo incluiu 31 portadores da SDFP, com idade entre 18 e 39 anos (24,29 ± 4,09), sendo 27 sujeitos do sexo feminino e quatro, do masculino. Todos os sujeitos foram submetidos às escalas KOS e IKDC em duas ocasiões. A segunda aplicação serviu como prova de confiabilidade (PCKOS e PCIKDEC). A análise de correlação estatística entre as duas escalas foi realizada com os testes de Spearman e Wilcoxon, considerando-se significativo p < 0,05. RESULTADOS: O teste de correlação de Spearman revelou forte correlação entre KOS e PCKOS (r = 0,99; p < 0,001) e IKDC e PCIKDC (r = 0,96; p < 0,001). Houve uma moderada correlação entre KOS e IKDC (r = 0,46; p < 0,01) e PCKOS e PCIKDC (r = 0,55; p < 0,002). O teste de Wilcoxon revelou diferença entre KOS e IKDC (p < 0,001) e entre PCKOS e PCIKDC (p < 0,001). Houve igualdade entre KOS e PCKOS (p > 0,10) e diferença entre IKDC e PCIKDC (p < 0,02). CONCLUSÃO: As escalas KOS e IKDC apresentaram-se confiáveis durante o processo de aplicação nos portadores da SDFP, recebendo a KOS a prova de maior confiabilidade quando comparada ao IKDC.

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.

Motor-neuron pool excitability of the lower leg muscles after acute lateral ankle sprain

CONTEXT

Neuromuscular deficits in leg muscles that are associated with arthrogenic muscle inhibition have been reported in people with chronic ankle instability, yet whether these neuromuscular alterations are present in individuals with acute sprains is unknown.

OBJECTIVE

To compare the effect of acute lateral ankle sprain on the motor-neuron pool excitability (MNPE) of injured leg muscles with that of uninjured contralateral leg muscles and the leg muscles of healthy controls.

DESIGN

Case-control study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Ten individuals with acute ankle sprains (6 females, 4 males; age= 19.2 ± 3.8 years, height= 169.4 ± 8.5 cm, mass= 66.3 ± 11.6 kg) and 10 healthy individuals(6 females,4 males; age= 20.6 ± 4.0 years, height = 169.9 ± 10.6 cm, mass= 66.3 ± 10.2 kg) participated.

INTERVENTION(S)

The independent variables were group (acute ankle sprain, healthy) and limb (injured, uninjured). Separate dependent t tests were used to determine differences in MNPE between legs.

MAIN OUTCOME MEASURE(S)

The MNPE of the soleus, fibularis longus, and tibialis anterior was measured by the maximal Hoffmann reflex (H(max)) and maximal muscle response (M(max)) and was then normalized using the H(max):M(max) ratio.

RESULTS

The soleus MNPE in the ankle-sprain group was higher in the injured limb (H(max):M(max) = 0.63; 95% confidence interval [Cl],0.46, 0.80) than the uninjured limb (H(max):M(max) = 0.47; 95%Cl, 0.08, 0.93)(t(6) = 3.62,P =.01).In the acute ankle-sprain group, tibialis anterior MNPE tended to be lower in the injured ankle (H(max):M(max) =0.06; 95% Cl, 0.01, 0.10) than in the uninjured ankle (H(max):M(max) =0.22; 95%Cl, 0.09, 0.35),but this finding was not different (t(9) =-2.01, P =.07). No differences were detected between injured (0.22; 95% Cl, 0.14, 0.29) and uninjured (0.25; 95%Cl, 0.12, 0.38) ankles for the fibularis longus in the ankle-sprain group (t(9) =-0.739, P =.48). We found no side-to-side differences in any muscle among the healthy group.

CONCLUSIONS

Facilitated MNPE was present in the involved soleus muscle of patients with acute ankle sprains, but no differences were found in the fibularis longus or tibialis anterior muscles.

Evoked spinal reflexes and force development in elite athletes with middle-portion Achilles tendinopathy

STUDY DESIGN

Controlled laboratory study.

OBJECTIVES

To compare the neuromuscular function of the triceps surae muscle bilaterally in elite athletes with unilateral chronic Achilles tendinopathy.

BACKGROUND

Previous studies suggest that tendinopathies or chronic pain may lead to a spinal/supraspinal level modulation of the excitability or voluntary activation of ipsilateral motor units. However, this has not been studied in Achilles tendinopathy.

METHODS

Fourteen college athletes (mean ± SD age, 24.2 ± 1.7 years) who had unilateral chronic middle-portion tendinopathy in their Achilles tendons were recruited. Bilateral measurements of soleus reflex tests, including H-reflex and V wave, and rate of force development (RFD), as well as corresponding electromyography of the tibialis anterior and triceps surae muscles, were performed. Statistical within-subject and between-leg comparisons were made.

RESULTS

In the leg with tendinopathy, the V wave of the soleus muscle was significantly increased (P<.001). The side with tendinopathy also had a reduced normalized RFD (0-30, 0-50, and 0-100 ms) in plantar flexion, and concomitant higher electromyography ratios between the tibialis anterior and soleus (0-30 and 0-50 milliseconds) during the early stage of explosive contractions (P<.05). No significant differences were found for H-reflex, maximal plantar flexion and dorsiflexion torque, and absolute RFD.

CONCLUSIONS

Higher volitional supraspinal reflexes and lower maximal-strength independent force development occur in the triceps surae of elite athletes with unilateral middle-portion Achilles tendinopathy. These changes potentially indicate an acquired compensatory mechanism for maximal force production and deficits in explosive strength. The RFD is also suggested as a sensitive parameter to depict neuromuscular changes during treatment of chronic tendinopathies.

Effects of joint effusion on proprioception in patients with knee osteoarthritis: a single-blind, randomized controlled clinical trial

OBJECTIVE

To assess the effects of joint effusion on proprioceptive status in patients with knee osteoarthritis (OA).

DESIGN

A single-blind, randomized, controlled clinical trial in 40 female subjects aged 50 years and over with painful knee OA. All subjects were randomly assigned to either the control or experimental group. A volume of 20 mL of normal saline was injected into the knee joint cavity of subjects in the experimental group under ultrasonographic guidance. Proprioceptive acuity was assessed by active repositioning of the lower limb using an electrogoniometer to measure knee joint position sense (JPS) under both non-weight-bearing (NWB) and weight-bearing (WB) conditions twice, with a 20-min rest interval. The experimental group performed the task twice (Test 1 and Test 2) before and within 5 min after joint infusion. The control group also performed Test 1 and Test 2 without joint infusion. The outcome of interest was the absolute angular error (AAE), ignoring the direction of the error, between the randomized target angle and the patient's reproduced angle of JPS values.

RESULTS

Compared with the control group, JPS was significantly compromised in the experimental group in the NWB test after joint infusion (P=0.025). However, no significant differences in the angular error were observed between Test 1 and Test 2 in the control group for the NWB or WB test or in the experimental group for the WB test after infusion (P>0.05).

CONCLUSIONS

This study showed that joint effusion impairs proprioceptive function in osteoarthritic knee joints.

Cryotherapy to treat persistent muscle weakness after joint injury

Cryotherapy is a widely used modality following acute joint injury. It is considered helpful in reducing pain and swelling, and there is a growing body of evidence to suggest that it may have additional benefits in muscle function. Following joint injury, it is common for patients to experience persistent muscle weakness that is resistant to traditional strengthening exercises. This may be due to a reflex inhibition of musculature surrounding the injured joint. The underlying cause of this reflex inhibition may arise from aberrant sensory information from the joints' neural receptors, which result in a neural inhibition of motor neurons. This inhibition is beyond conscious control, is ongoing, and impedes normal joint function via a disruption of normal muscle function. Cryotherapy treatments targeted at peripheral joints have been shown to result in transient resolution of reflex inhibition, which thereby provide an environment where injured patients can benefit from a more thorough motorneuron pool during controlled rehabilitation exercises. This article presents current evidence-based recommendations regarding the use of joint cryotherapy for maximizing the effectiveness of commonly used rehabilitation exercises in patients recovering from joint injury.

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.

Quadriceps inhibition induced by an experimental knee joint effusion affects knee joint mechanics during a single-legged drop landing

BACKGROUND

Arthrogenic quadriceps muscle inhibition accompanies knee joint effusion and impedes rehabilitation after knee joint injury.

HYPOTHESIS

We hypothesized that an experimentally induced knee joint effusion would cause arthrogenic quadriceps muscle inhibition and lead to increased ground reaction forces, as well as sagittal plane knee angles and moments, during a single-legged drop landing.

STUDY DESIGN

Controlled laboratory study.

METHODS

Nine subjects (4 women and 5 men) underwent 4 conditions (no effusion, lidocaine injection, "low" effusion [30 mL], and "high" effusion [60 mL]) and then performed a single-legged drop landing. Lower extremity muscle activity, peak sagittal plane knee flexion angles, net sagittal plane knee moments, and peak ground reaction forces were measured.

RESULTS

Vastus medialis and lateralis activity were decreased during the low and high effusion conditions (P < .05). However, increases in peak ground reaction forces and decreases in peak knee flexion angle and net knee extension moments occurred only during the high effusion condition (P < .05).

CONCLUSIONS

Knee joint effusion induced quadriceps inhibition and altered knee joint mechanics during a landing task. Subjects landed with larger ground reaction forces and in greater knee extension, thereby suggesting that more force will be transferred to the knee joint and its passive restraints when quadriceps inhibition is present.

CLINICAL RELEVANCE

Knee joint effusion results in arthrogenic quadriceps muscle inhibition, increasing loading about the knee that may potentially increase the risk of future knee joint trauma or degeneration.

Vastus Medialis H-Reflex Reliability During Standing

Vastus medialis H-reflex is a valid measure to examine quadriceps muscle voluntary activation and inhibition after knee injury. Its reliability during repeated sessions has not been established. The purpose of this study was to establish the intrasession and intersession reliability of vastus medialis H-reflex amplitude recordings during standing with varied knee flexion angles (0, 30, 45, and 60 degrees). Electromyography unit was used to elicit and record the vastus medialis H-reflex from the right leg of five healthy subjects. The femoral nerve was stimulated using 0.5-millisecond pulses at 0.2 pps of H-maximum. Four recordings of the vastus medialis H-reflex amplitude were recorded in three trials for each knee flexion angle within each session for two consecutive days. Reliability was calculated using intraclass correlation coefficients (ICC). Intrasession reliability during standing with varied knee angles was high (ICC [2, 4] range from 0.76 to 0.98), and intersession reliability during standing with varied knee angles was moderate to high (ICC [2, 1] range from 0.51 to 0.84). Recording four traces of vastus medialis H-reflex amplitude per trial was reliable. Vastus medialis H-reflex amplitude recordings while standing during varied knee flexion are reliable within and between sessions.

The anterior cruciate ligament deficiency as a model of brain plasticity

This paper describes a plausible mechanism for the development of brain plastic changes due to a peripheral joint injury, such as anterior cruciate ligament (ACL) rupture. Evidence for the hypothesis is based on mainly three indications derived from the literature review: (a) the existence of two different categories of ACL patients, the copers and non-copers, presenting different features of functional deficiencies, (b) the demand of a sufficient post-traumatic time (more than 6 months) for the dysfunction development and (c) the fact that the dysfunction is not limited to the injured limb but also concerns the non-injured one. Considering the fact that ACL contains mechanoreceptors, which inform the central nervous system (CNS) about joint sense position and kinaesthesia, it can be suggested that this kind of injury might be regarded as a neurophysiological dysfunction, not being a simple musculoskeletal injury. The rupture of the ACL could lead to the cessation/depletion or differentiation of the ascending afferent pathway from the injured joint towards CNS, inducing to the joint de-afferentation and consequently CNS reorganization and joint de-efferentation. In case of presumable evidence of the proposed hypothesis, its clinical application could concern several aspects of the intervention procedures. For example, a number of clinical findings, such as the functional differences presented between two separate clinical groups of patients (copers and non-copers) could be justified or the rehabilitation strategies might have to be revised, provided that certain therapeutic components have influence on facilitating brain plastic changes that induce to beneficial functional outcomes.

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

Knee joint effusion results in quadriceps inhibition and is accompanied by increased excitability in the soleus musculature. The purpose of this study was to determine if soleus arthrogenic muscle response is regulated by pre- or post-synaptic spinal mechanisms. Ten healthy adults (two females and eight males) were measured on two occasions. At the first session, subjects had their knee injected with 60 ml of saline and in the other session they did not. Pre- and post-synaptic spinal mechanisms were measured at baseline, immediately following a needle stick, immediately following a Xylocaine injection, and 25 and 45 min post-saline injection. A mixed effects model for repeated measures was used to analyze each dependent variable. The a priori alpha level was set a P < or = 0.05. The percentage of the unconditioned reflex amplitude for recurrent inhibition (P < 0.0001) and reflex activation history (P < 0.0001) significantly increased from baseline at 25 and 45 min post-effusion. Soleus arthrogenic muscle response seen following knee joint effusion is mediated by both pre- and post-synaptic mechanisms. In conclusion, the arthrogenic muscle response seen in the soleus musculature following joint effusion is regulated by both pre- and post-synaptic control mechanisms. Our data are the first step in understanding the neural networks involved in the patterned muscle response that occurs following joint effusion.

An experimental knee joint effusion does not affect plasma catecholamine concentration in humans

Knee joint effusion causes quadriceps inhibition and is accompanied by increased soleus muscle excitability. In order to reverse the neurological alterations that occur to the musculature following effusion, we need to understand the extent of neural involvement. Ten healthy adults were tested on two occasions; during one session, subjects had their knees injected with saline and in the other admission, they did not. Soleus Hmax, Mmax, plasma epinephrine, and norepinephrine concentrations were obtained at five intervals. Results showed that Hmax increased following the effusion, while norepinephrine and epinephrine levels were not altered. We suggest that the soleus facilitation seen following knee effusion results from stimulation of joint mechanoreceptors and removal of descending spinal and supraspinal inhibition and is not the result of a sympathetic response.

The effect of a simulated knee joint effusion on postural control in healthy subjects

OBJECTIVE

To determine the effects of a simulated knee joint effusion on center of pressure (COP) path and mean power frequency (MPF) during standing.

DESIGN

Quasi-experimental design.

SETTING

Sports injury research laboratory in a university setting.

PARTICIPANTS

Twenty healthy volunteers, 10 of whom (age, 20.1+/-2.4y; height, 168.0+/-8.1cm; weight, 70.4+/-13.3kg) were assigned to an effusion group and 10 of whom (age, 25+/-3.8y; height, 169.4+/-8.9cm; weight, 74.7+/-7.7kg) were assigned to a control group.

INTERVENTIONS

COP data were collected before and after a 60-mL injection of sterile saline into the knee joint space.

MAIN OUTCOME MEASURES

COP path and mediolateral and anteroposterior MPF.

RESULTS

COP path decreased after the effusion (pre-effusion mean, 92.2+/-21.9cm; posteffusion mean, 77.27+/-23.0cm). No change was found within the control group for COP path (P>.05). No differences were detected before or after joint effusion when the MPF was examined (P>.05).

CONCLUSIONS

Possible explanations for the improved postural control after the effusion include additional somatosensory feedback, an augmented neural drive to the soleus, and/or increased capsular tension.

Ankle cryotherapy facilitates soleus function

STUDY DESIGN

A 2-factor (group and time) experimental design with repeated measures on time.

OBJECTIVES

To determine the effects of ankle cryotherapy on voluntary and resting motor function of the soleus over a 60-minute period. To determine if a relationship exists between changes in torque production and Hoffmann reflex (H-reflex) following ankle joint cryotherapy treatment.

BACKGROUND

Controversy surrounds the use of cryotherapy prior to activity and rehabilitation. While cooling muscle may have a deleterious effect on motor function, cooling the joint may enhance motor function around the joint. The H-reflex is a good resting measure of motoneuronal activity. However, its relationship to voluntary activity is unknown.

METHODS AND MEASURES

Thirty subjects were pretested (baseline) for normalized H-reflex (defined as the ratio of maximum H-reflex [Hmax] to maximum direct motor response [Mmax]) and peak plantar flexion torque. A crushed ice bag was placed over the ankle of 15 subjects for 30 minutes. H-reflex and torque measurements were collected immediately following the cryotherapy treatment at 30, 60, and 90 minutes. Surface temperatures were recorded from the ankle and electrode site with each measurement interval.

RESULTS

Both peak H-reflex and plantar flexion torque at 30, 60, and 90 minutes increased relative to baseline measurements. Each measurement was also greater than the corresponding control at 30, 60, and 90 minutes. A weak correlation (r = 0.38; P = 0.036) existed between changes in H-reflex and plantar flexion torque at 30 minutes.

CONCLUSIONS

The soleus motoneuron pool is facilitated following a 30-minute crushed ice application to the ankle and over a 60-minute postcooling period. These data support the use of joint cooling prior to activity and rehabilitation.