Arthrogenic muscle inhibition after ACL reconstruction: a scoping review of the efficacy of interventions

Time course of Quadriceps thickness changes over six months post-anterior cruciate ligament reconstruction: Unveiling critical impairments in vastii muscles

Vastii muscle adaptation caused by Quadriceps weakness observed after an Anterior Cruciate Ligament reconstruction (ACLr) remain debatable. We described the time course of changes in Quadriceps thickness, strength, and thigh circumference over six months following an ACLr. Quadriceps thicknesses, Quadriceps strength, and thigh circumference were measured preoperative, 3, and 6 months post-ACLr surgery in 103 patients (77 men and 26 women). Limbs and time were compared with repeated-measures ANOVA and the Intra-class correlation coefficient was determined (α = 5 %). From 0 to 3 months post-surgery, Quadriceps strength (p < 0.05), and VI (p < 0.05) and VL (p < 0.001) thicknesses were reduced. From 3 to 6 months, Quadriceps strength (p < 0.05), total Quadriceps thickness (p < 0.001), and VI (p < 0.001) and VL (p < 0.05) thicknesses increased. VM and RF thicknesses increase to 3 months after ACLr (p < 0.05). Quadriceps strength, circumference at 5 cm, VI, VL, VM, and total Quadriceps thickness remain lower than the contralateral limb 6 months following an ACLr (p < 0.05). Quadriceps thickness adapts heterogeneously, with VI and VL atrophying for up to three months, developing the highest Quadriceps weakness. By 6 months, VI does not recover its thickness proportion, and VI and VL do not return to pre-surgery conditions. Both vastii muscles align with Quadriceps strength changes over six months posterior ACLr.

Editorial Commentary: Failure to Regain Full Hyperextension After Anterior Cruciate Ligament Reconstruction Is Associated With Inferior Patient Satisfaction and Lower Functional Outcomes Scores, But the Impact on Graft Rupture Rates and Persistent Instability Is Unclear

Up to one half of patients undergoing anterior cruciate ligament reconstruction demonstrate some degree of knee hyperextension in their contralateral limb. In most cases, this is mild (1°-5°), but it is reported that 9% and 0.8% demonstrate moderate (6°-10°) and severe (>10°) degrees of hyperextension. These characteristics pose challenges and considerations for surgical management. This includes the finding that failure to regain full hyperextension is common and is associated with inferior functional outcomes and patient satisfaction, and the juxtaposition that regaining full hyperextension may increase graft rupture and persistent instability rates. Although the pathophysiology of extension deficit is multifactorial, 2 particularly important and modifiable risk factors in this population are notch impingement and arthrogenic muscle inhibition. Strategies to avoid notch impingement include anterior notchplasty and careful consideration of graft size, graft type, and tibial tunnel placement. Arthrogenic muscle inhibition is clinically characterized by extension deficit and quadriceps activation failure. It is reversible in most patients and therefore an important modifiable risk factor. Since failure to regain full hyperextension is associated with inferior outcomes, abolishing extension deficit should be a key objective of surgical treatment and rehabilitation. Concerns regarding the risks of persistent laxity and graft rupture in knee hyperlaxity/hyperextension patients can be mitigated by the addition of anterolateral ligament reconstruction.

Rethinking the Assessment of Arthrogenic Muscle Inhibition After ACL Reconstruction: Implications for Return-to-Sport Decision-Making-A Narrative Review

Arthrogenic muscle inhibition (AMI) is a neuromuscular impairment commonly observed following anterior cruciate ligament reconstruction (ACLR). This condition, characterized by persistent quadricep inhibition due to altered afferent feedback, significantly impacts neuromuscular recovery, delaying return to running and sport. Despite advancements in rehabilitation strategies, AMI may persist for months or even years after ACLR, leading to muscle strength asymmetries, altered biomechanics, and an increased risk of reinjury. The mechanisms underlying AMI involve both peripheral (joint effusion, mechanoreceptor dysfunction) and central (corticospinal inhibition, neuroplasticity alterations) components, which collectively hinder voluntary muscle activation and movement control. AMI alters gait mechanics, reduces knee stability, and promotes compensatory patterns that increase injury risk. Current return-to-sport protocols emphasize strength symmetry and functional performance but often neglect neuromuscular deficits. A comprehensive assessment integrating neuromuscular, biomechanical, and proprioceptive evaluations is needed at specific stages to optimize rehabilitation and minimize reinjury risk. Future research should explore targeted interventions such as neuromuscular stimulation, cognitive-motor training, and advanced gait analysis to mitigate AMI's impact and facilitate a safer, more effective return to sport.

Nutritional Interventions to Attenuate Quadriceps Muscle Deficits following Anterior Cruciate Ligament Injury and Reconstruction

Following anterior cruciate ligament (ACL) injury, quadriceps muscle atrophy persists despite rehabilitation, leading to loss of lower limb strength, osteoarthritis, poor knee joint health and reduced quality of life. However, the molecular mechanisms responsible for these deficits in hypertrophic adaptations within the quadriceps muscle following ACL injury and reconstruction are poorly understood. While resistance exercise training stimulates skeletal muscle hypertrophy, attenuation of these hypertrophic pathways can hinder rehabilitation following ACL injury and reconstruction, and ultimately lead to skeletal muscle atrophy that persists beyond ACL reconstruction, similar to disuse atrophy. Numerous studies have documented beneficial roles of nutritional support, including nutritional supplementation, in maintaining and/or increasing muscle mass. There are three main mechanisms by which nutritional supplementation may attenuate muscle atrophy and promote hypertrophy: (1) by directly affecting muscle protein synthetic machinery; (2) indirectly increasing an individual's ability to work harder; and/or (3) directly affecting satellite cell proliferation and differentiation. We propose that nutritional support may enhance rehabilitative responses to exercise training and positively impact molecular machinery underlying muscle hypertrophy. As one of the fastest growing knee injuries worldwide, a better understanding of the potential mechanisms involved in quadriceps muscle deficits following ACL injury and reconstruction, and potential benefits of nutritional support, are required to help restore quadriceps muscle mass and/or strength. This review discusses our current understanding of the molecular mechanisms involved in muscle hypertrophy and disuse atrophy, and how nutritional supplements may leverage these pathways to maximise recovery from ACL injury and reconstruction.

Neurophysiology of ACL Injury

The neurophysiology of ACL injury extends beyond the mechanical rupture of the ligament to encompass profound alterations in the central and peripheral nervous systems, impacting sensorimotor integration and neuromuscular control. The ACL, densely populated with mechanoreceptors, plays a critical role in joint proprioception, dynamically regulating knee stability through complex neural circuits that connect to the spinal cord and brain. When disrupted by injury, these neural pathways contribute to delayed muscular activation, altered motor planning, and compromised joint stability. Such neuromechanical deficits increase the likelihood of reinjury and highlight the need for comprehensive neuroplastic rehabilitation. Neuroplastic therapy, employing tools like external focus strategies, stroboscopic glasses, smartboards, and virtual reality, aims to restore and enhance neural connectivity, sensory integration, and motor coordination. These advanced tools target distinct phases of motor learning, promoting automaticity and resilience in movement patterns. By integrating visual-cognitive, proprioceptive, and reflexive controls, this therapeutic approach not only accelerates recovery but also optimizes performance and reduces the risk of re-injury, representing a paradigm shift in ACL rehabilitation.

Hamstrings and Quadriceps Weaknesses Following Anterior Cruciate Ligament Reconstruction Persist Up to 6 Months After Return-to-Sport: An Angle-specific Strength Analysis

BACKGROUND

Hamstrings and quadriceps strength recovery and restoration of the hamstrings-to-quadriceps ratio (H/Q ratio) is a major concern after anterior cruciate ligament reconstruction (ACLR). Recently, moment-angle profiles and angle-specific H/Q ratios are receiving increasing interest.

PURPOSE

The first objective of this study was to investigate moment-angle profiles and angle-specific H/Q ratio profiles in athletes with ACLR at the time of RTS. The second objective of this study was to assess whether strength asymmetries identified at the time of RTS, persist after six months.

STUDY DESIGN

Case-Control study.

METHODS

Twenty athletes who had undergone ACLR performed isokinetic strength tests for concentric knee flexion and extension (60°/s) at RTS, and three and six months later. Twenty controls were tested once. T-tests were used to compare strength differences between 1) ACLR athletes and controls and 2) the injured and uninjured leg of the ACLR athletes. Finally, to assess strength deficits over time, two-way ANOVAs were used.

RESULTS

Angle-specific analyses and peak moments showed lower hamstrings strength in the injured leg of ACLR athletes compared to their uninjured leg at RTS. Furthermore, angle-specific analyses showed a lower hamstrings strength and H/Q ratio in the injured leg compared to controls at larger knee flexion angles. The latter deficit was not identified with a peak-based analysis. The asymmetries identified at RTS did not change over the six months following RTS.

CONCLUSIONS

Athletes with ACLR show strength deficits and asymmetries that persist even six months after RTS. As some asymmetries may go undetected by peak-based analyses, angle-specific analyses are recommended.

LEVEL OF EVIDENCE

Level 3b.

[Effectiveness of muscles' preoperative preparation for reconstruction of anterior cruciate ligament of knee]

The most common knee injury in professional athletes is anterior cruciate ligament (ACL) trauma, requiring surgical intervention and subsequent long-term rehabilitation. Arthrogenic muscle inhibition, immediately following injury in some cases, leads to quadriceps muscle hypotrophy and weakness, that further embarrasses the athlete's good-quality rehabilitation.

OBJECTIVE

To assess clinical and functional effectiveness of passive electrical myostimulation (EMS) as a muscle preoperative preparation to autotransplantation of knee anterior cruciate ligament.

MATERIAL AND METHODS

The study involved 47 male athletes with ACL injury. Summarized surface electromyography (EMG) was performed in all participants at admission, as a result of which 28 patients with reduced EMG parameters were selected. Among them, 14 patients received a course of passive EMS of quadriceps on physiotherapeutic INTELECT Advanced (Chattanooga (DJO), USA) hardware. All patients got passive EMS for 2 weeks after surgery and started active muscle training since 3rd week. Clinical and functional effectiveness was evaluated in dynamics in 2 and 7 weeks after surgery.

RESULTS

The 10-day preoperative course of EMS made it possible to significantly increase values of mean amplitude (MA) of muscle contraction before surgery and improve indicators of clinical and functional tests in 7 weeks after surgery up to level of healthy subjects and patients group with normal MA values at baseline compared to patients who did not have preoperative passive myostimulation.

CONCLUSION

The obtained data allow to recommend the inclusion of passive EMS method of quadriceps as a preoperative training of patients with ACL injury and reduced EMG.

Reduced physiological extrusion of the medial meniscus in axial load-bearing condition in anterior cruciate ligament deficiency

PURPOSE

In this study, ultrasonography was used to measure medial meniscus (MM) extrusion under weight-bearing and nonweight-bearing conditions in both anterior cruciate ligament (ACL)-deficient and ACL-intact knee groups. This study aimed to determine the possible differences between these groups with an eventual impact on meniscal tears in ACL-deficient knees.

METHODS

A total of 107 patients who underwent ACL reconstructive surgery between June 2022 and April 2023 were enroled. After applying exclusion criteria, 37 patients met the conditions for inclusion in the study and formed the ACL deficiency group (Group D). Of the 141 patients presenting to an outpatient clinic who agreed to have ultrasonography conducted on their nondiscomforting contralateral knee, 37 patients matched for age, sex, hip-knee-ankle angle and body mass index with Group D patients were selected for the ACL intact group (Group I). Ultrasonography was used to measure MM extrusion in weight-bearing and nonweight-bearing conditions for all participants.

RESULTS

Seventy-four patients were included in the study (n = 37 per group). The supine position showed an MM extrusion of 1.2 ± 0.7 mm in Group I and 1.2 ± 0.7 mm in Group D (not significant). In the standing position, MM extrusion measured 2.0 ± 0.6 mm in Group I and 1.3 ± 0.8 mm in Group D. The difference in extrusion (Δextrusion) between the two positions was 0.8 ± 0.6 in Group I and 0.1 ± 0.2 in Group D, with statistical significance (p < 0.01). A consistent reduction in MM extrusion during weight-bearing was observed in patients with ACL deficiency, irrespective of the duration of ACL deficiency, age, sex and BMI.

CONCLUSION

ACL deficiency did not significantly impact MM extrusion during nonweight-bearing conditions; however, less MM extrusion was observed in response to axial loading conditions. These findings indicate altered MM biomechanics due to increased anterior-posterior meniscal motion and rotational instability after ACL injury.

LEVEL OF EVIDENCE

Level III.

High-Density Surface Electromyography Feedback Enhances Fibularis Longus Recruitment in Chronic Ankle Instability

PURPOSE

This study aimed to determine whether individuals with chronic ankle instability (CAI) can activate the fibularis longus compartments with high-density surface electromyography (HD-sEMG) biofeedback to the same extent as those without CAI, and to analyze the effect of ankle position on compartment activation in individuals with CAI using HD-sEMG feedback.

METHODS

There were 16 volunteers per group (CAI and No-CAI). The sEMG amplitude at each compartment (anterior and posterior) and the barycenter of the spatial sEMG amplitude distribution of the fibularis longus were recorded during eversion in neutral and plantar flexion positions at 30% and 70% of maximum voluntary contraction force, both with and without visual feedback on the spatial sEMG amplitude distribution.

RESULTS

sEMG amplitude of the posterior compartment of the fibularis longus in the CAI group trained with HD-sEMG feedback during eversion at 70% maximum voluntary contraction (in plantar flexion) was significantly higher than without HD-sEMG feedback (95% CI = 3.75-34.50% root mean square) and was similar to the activation of the No-CAI group (95% CI = -14.34% to 34.20% root mean square). Furthermore, individuals with CAI who underwent training with HD-sEMG feedback in plantar flexion exhibited a posterior displacement of the barycenter (95% CI = 0.56-2.84 mm).

CONCLUSIONS

Utilizing HD-sEMG feedback during eversion in plantar flexion position increases activation of the fibularis longus posterior compartment in individuals with CAI to the same extent as healthy people. HD-sEMG-based topographic maps can serve as effective feedback training to restore motor control of the ankle. Long-term efficacy for improving motor function requires investigation through longitudinal studies.

Anodal transcranial direct current stimulation (tDCS) modulates quadriceps motor cortex inhibition and facilitation during rehabilitation following anterior cruciate ligament (ACL) reconstruction: a triple-blind, randomised controlled proof of concept trial

Objectives

Following anterior cruciate ligament reconstruction (ACLR), maladaptive changes occur in the motor cortex representation of the quadriceps, evidenced by increases in intracortical inhibition and facilitation. The primary objective of this proof-of-concept study was to determine if anodal transcranial direct current stimulation (tDCS) can alter quadriceps intracortical inhibition and facilitation in an early-ACLR population after 6 weeks of application during exercise.

Methods

We performed a randomised, triple-blind controlled trial for proof of concept comparing anodal-tDCS to sham-tDCS following ACLR. Anodal-tDCS or sham-tDCS was delivered to the primary motor cortex for 20 min, three times per week, for 6 weeks from week 2 post ACLR. Transcranial magnetic stimulation quantified quadriceps short-interval intracortical inhibition (SICI), long-interval intracortical inhibition (LICI) and short-interval intracortical facilitation (SICF). Significance at p<0.05.

Results

Participants were randomised to anodal (n=11) or sham (n=10) tDCS. Participants were predominantly male (n=13) and had a mean (SD) age of 24.4 (4.7) years. For SICI, there was a group-by-time effect for anodal-tDCS (β=0.519, 95% CI 0.057 to 0.981, p=0.028) and an effect for time (β=-1.421, 95% CI -1.919 to -0.923, p<0.001). For LICI, there was no group-by-time (β=-0.217, 95% CI -0.916 to 0.482, p=0.543) or time effect (β=0.039, 95% CI -0.815 to -0.893, p=0.928). For SICF, there was a group-by-time effect for anodal-tDCS (β=-0.764, 95%CI -1.407 to -0.120, p=0.020) but not time (β=0.504, 95% CI -0.627 to 1.635, p=0.383).

Conclusion

This study provided proof of the efficacy of anodal-tDCS post ACLR in reducing maladaptive quadriceps inhibition and facilitation. We demonstrated anodal-tDCS improved facilitation and inhibition post ACLR, which are drivers of arthrogenic muscle inhibition.

The Effect of Physiotherapy on Arthrogenic Muscle Inhibition After ACL Injury or Reconstruction: A Systematic Review

Arthrogenic muscle inhibition (AMI) following ACL injury or reconstruction is a common issue that affects muscle activation and functional recovery. Thus, the objective of this study was to systematize the literature on the effects of physiotherapy interventions in the rehabilitation of AMI after ACL injury or reconstruction. A systematic review was conducted following the PRISMA guidelines. The risk of bias was evaluated using the PEDro scale and the Cochrane risk of bias tool. Searches were performed in the PubMed, Google Scholar, Cochrane Library, and EMBASE databases. Randomized controlled trials involving patients with ACL injuries or ACL reconstruction were included. Twenty studies were included. Fifteen evaluated the effects of exercise, showing significant improvement. Seven studies examined electrotherapy, with neuromuscular electrical stimulation and high-frequency therapy combined with exercise showing improvements in muscle strength, pain, and joint range of motion. Nine studies explored interventions like motor imagery, cryotherapy, taping, and vibration. When performed before exercise, motor imagery and cryotherapy improved cortical activity and muscle recovery. Kinesio taping reduced edema and pain better than exercise alone. Vibration showed inconsistent results across three studies. Methodological quality varied between 5 and 8 on the PEDro scale, with moderate-to-low risk of bias. Structured exercise should be the first-line intervention, but combining it with other therapies enhances rehabilitation. The study protocol was registered in the PROSPERO database (CRD42023425510).

Treatment of Arthrogenic-Muscle-Inhibition in patients after knee-surgery with Motion-Activated-Neuromuscular stimulation - a case-series

Arthrogenic muscle inhibition (AMI) presents a persistent challenge in postoperative knee rehabilitation and is often resistant to standard care. This case series examines the efficacy of Motion-Activated Neuromuscular Electrical Stimulation (mNMES) in addressing AMI refractory to rehabilitation after ACL (revision) surgery, patellar dislocation, trochleoplasty, or conservative treatment of the patellofemoral pain syndrome. Eight patients who had undergone extensive unsuccessful rehabilitation received six weeks of a novel mNMES treatment regimen. Outcome assessments included patient-reported outcome measures (PROMs) and AMI classification. Results revealed significant improvements in pain reduction, knee function, and AMI reduction. Despite study limitations, mNMES demonstrated promising outcomes and could be used as an adjunct to standard rehabilitation, offering potential for enhancing postoperative outcomes in patients refractory to conventional therapy. Further research is required to validate these findings and optimise treatment protocols.

Joint Effusion at 3 Months After Anterior Cruciate Ligament Reconstruction: Its Risk Factors and Association With Subsequent Muscle Strength and Graft Remodeling

Background

Joint effusion at 3 months after anterior cruciate ligament (ACL) reconstruction is a risk factor for ACL reinjury. However, factors associated with joint effusion at 3 months postoperatively and the effect of joint effusion on subsequent quadriceps muscle strength and graft remodeling remain unknown.

Purposes

To identify factors associated with joint effusion and investigate the association between joint effusion and quadriceps muscle strength and graft remodeling in the postoperative period.

Study Design

Case-control study; Level of evidence, 3.

Methods

In this retrospective multicenter study, the medical records of patients who underwent single-bundle ACL reconstruction between 2015 and 2021 were reviewed. The study included the data of 174 patients (mean age, 23.5 ± 10.6 years). Demographic data, including sex, age at surgery, time from injury to surgery in months, body mass index, preinjury Tegner activity score, presence of meniscus, and chondral injuries, were collected. Magnetic resonance imaging was performed 3 months postoperatively. Joint effusion was defined as grade 3 (range of grades, 0-3) according to the ACL Osteoarthritis Score. Isokinetic strength testing was performed at 60 deg/s, while the limb symmetry index (LSI) of quadriceps strength was evaluated at 6 months postoperatively. Moreover, graft remodeling was evaluated using magnetic resonance imaging-derived signal intensity ratio (SIR) measures at 1 year postoperatively. The authors used multivariate logistic and linear regression analyses to identify the factors influencing joint effusion at 3 months and those associated with postoperative quadriceps strength LSI and SIR values, respectively.

Results

Greater preinjury Tegner activity scores (odds ratio, 1.59; 95% CI, 1.08 to 2.34; P = .02) increased the odds of joint effusion at 3 months postoperatively. Multivariable linear regression analysis revealed that joint effusion (β = -23.8; 95% CI, -36.0 to -11.7; P < .001) was an independent factor associated with LSI of the quadriceps. Furthermore, joint effusion (β = 1.33; 95% CI, 0.53 to 2.14; P = .001) was associated with a higher SIR value of the reconstructed graft.

Conclusion

The preinjury Tegner activity score was a factor associated with joint effusion at 3 months postoperatively, and joint effusion was associated with subsequent muscle weakness and delayed graft remodeling.

Neural-Targeted Rehabilitation Strategies to Address Neuroplasticity After Joint Injury

In patients with musculoskeletal injury, changes have been observed within the central nervous system that contribute to altered movement planning. This maladaptive neuroplasticity potentially explains the clinical disconnect where residual neuromuscular dysfunction and high rates of reinjury are often observed even after individuals clear return-to-activity functional testing. An improved understanding of these neural changes could therefore serve as a guide for facilitating a more complete recovery and minimizing risk of reinjury. Therefore, we propose a paradigm of neural-targeted rehabilitation to augment commonly used therapeutic techniques targeting sensorimotor function to better address maladaptive plasticity. Although most treatments have the capability to modify neural function, optimizing these treatments and combining them with integrative therapies (eg, implementation of motor learning strategies, transcranial direct current stimulation) may enhance neural efficiency and facilitate return to activity in patients with musculoskeletal injury. To complete this model, consideration of affective aspects of movement and associated interventions must also be considered to improve the durability of these changes.

Oh, My Quad: A Clinical Commentary And Evidence-Based Framework for the Rehabilitation of Quadriceps Size and Strength after Anterior Cruciate Ligament Reconstruction

Quadriceps weakness after anterior cruciate ligament reconstruction (ACLR) is a well-known phenomenon, with more persistent quadriceps weakness observed after ACLR with a bone-patellar tendon-bone or quadriceps tendon autograft than with a hamstring tendon autograft. Longstanding quadriceps weakness after ACLR has been associated with suboptimal postoperative outcomes and the progression of radiographic knee osteoarthritis, making the recovery of quadriceps size and strength a key component of ACLR rehabilitation. However, few articles have been written for the specific purpose of optimizing quadriceps size and strength after ACLR. Therefore, the purpose of this review article is to integrate the existing quadriceps muscle basic science and strength training literature into a best-evidence synthesis of exercise methodologies for restoring quadriceps size and strength after ACLR, as well as outline an evidence-informed quadriceps load-progression for recovering the knee's capacity to manage the force-profiles associated with high-demand physical activity. Level of Evidence: 5.

Knee muscle strength and steadiness for individuals with anterior cruciate ligament reconstruction and knee osteoarthritis

BACKGROUND

Strength and neuromuscular decrements following knee musculoskeletal injury may accelerate knee osteoarthritis development. This study assessed isometric knee extensor and flexor strength and steadiness between individuals with knee injury, i.e., ligament reconstruction, and knee osteoarthritis to healthy age-matched controls.

METHODS

Four cohorts (1: knee injury and 2: age-matched controls, and 3: radiographic knee osteoarthritis and 4: age-matched controls) were recruited. Participants performed maximal voluntary isometric knee extensor and flexor contractions. Then, strength (e.g., peak and rate of torque development) and steadiness (e.g., peak power, mean, and median frequency) were derived from each raw torque-time curve and associated power spectral density. A Kruskal-Wallis H test and Spearman's rho correlation analysis assessed cohort differences and association between knee extensor and flexor strength and steadiness.

FINDINGS

The young adult control and knee injury cohorts exhibited greater knee extensor and flexor strength than the older, knee osteoarthritis cohort (p < 0.043). The knee injury cohort, despite being as strong as their healthy counterparts, were significantly less steady with a 92% increase in peak power frequency (p = 0.046). The osteoarthritis cohort exhibited 157% less total power compared to the knee injury and young control cohorts (p < 0.019). Knee extensor and flexor peak torque, rate of torque development, and mean torque exhibit a significant, positive relation with total power (p < 0.018).

INTERPRETATION

Individuals with knee injury and disease may exhibit weaker or less steady knee musculature, predisposing them to degenerative joint disease. Clinicians may need to restore knee extensor and flexor steadiness to facilitate better joint neuromuscular control.

Higher Unilateral Muscle Imbalance at the Contralateral Knee 6 Months after Anterior Cruciate Ligament Reconstruction

There are a considerable number of patients who, after anterior cruciate ligament reconstruction (ACL), suffer from relapses or reduced performance. Data collected from isokinetic dynamometry can provide useful information on the condition of the knee during rehabilitation. Seventy-one young sports patients with ACL reconstruction performed concentric (CON) isokinetic dynamometry (CON/CON 90°/s and CON/CON 240°/s) to assess the muscle strength of the quadriceps (Q) and hamstrings (H) in both knees at 6 months after ACL reconstruction. Limb symmetry index (LSI) and the H/Q ratio were calculated. Comparative statistical tests and multivariate regression were performed. At 90°/s, 57 patients (80.3%) had an LSI below 90% for quadriceps and 28 (60.6%) for hamstring. The number of imbalanced patients according to H/Q ratio was higher in the non-operated knee (n = 56, 78.9%) (p < 0.001). At 240°/s, 49 cases (69.1%) had LSI values above 90% for quadriceps and 37 (52.1%) for hamstrings. Regarding H/Q, imbalanced cases were higher in the non-operated limb (n = 60, 84.5%) (p < 0.001). Strength data at 6 months after ACL reconstruction and post-operative rehabilitation indicated greater unilateral (H/Q) muscle imbalance in the non-operated knee than in the operated knee. Most patients did not achieve the adequate LSI values.

Effects of Single-Joint Type Hybrid Assistive Limb in Knee Rehabilitation on Reduction of Pre-motor Time and Increased Rate of Fast Muscle Activation for Anterior Cruciate Regiment (ACL) Reconstruction

BACKGROUND/OBJECTIVES

Changes in muscle characteristics after post-anterior cruciate regiment (ACL) reconstruction are common. Knee robotic-assisted therapy using hybrid assistive limb (HAL) single-joint training for recovery from ACL injury has the potential to optimize muscle activity; however, its neurophysiological effects remain unclear. Thus, this study aimed to explore the electrophysiological parameters.

METHODS

This prospective, nonrandomized, controlled trial was conducted between December 2021 and January 2024. The patients were divided into two groups: the HAL group and the control group, each including five patients who underwent arthroscopic ACL reconstruction. Knee HAL single-joint training was conducted once weekly for three sessions. Three electrophysiological measures were examined related to knee neuromuscular responses pre-motor time, peak amplitude time, and neuromuscular rate of electromyography rise (RER) using surface electromyography (EMG). The pre-motor time and peak amplitude time were assessed in both groups at each session pre- and post-intervention. Both groups were evaluated for RER at postoperative weeks 17 and 21.

RESULTS

Regarding the interaction of pre-motor time within each group, the interaction of pre-motor time within each group, the effect size of vastus medialis (VM) was larger in the HAL group. The peak amplitude time of EMG, the overall estimated marginal means, and the HAL group exhibited a significant difference in the VM (p=0.019), while vastus lateralis (VL) showed no significant difference but a larger effect size (d=0.61). The RER revealed a significant difference in semitendinosus-RER30ms in the HAL group (p=0.044).

CONCLUSIONS

The knee HAL training for post-ACL reconstruction patients may influence neurophysiological outcomes.

Low-frequency sounds combined with motor imagery elicits a transient disruption of force performance: A path to neuromotor reprogramming?

The effectiveness of motor imagery (MI) training on sports performance is now well-documented. Recently, it has been proposed that a single session of MI combined with low frequency sound (LFS) might enhance muscle activation. However, the neural mechanisms underlying this effect remain unknown. We set up a test-retest intervention over the course of 2 consecutive days to evaluate the effect of (i) MI training (MI, n = 20), (ii) MI combined with LFS (MI + LFS, n = 20), and (iii) a control condition (CTRL, n = 20) on force torque produced across repeated maximal voluntary contractions of the quadriceps before (Pretest), after (Posttest) and at +12 h (Retention) post-intervention. We collected the integrated electromyograms of the quadriceps muscles, as well as brain electrical potentials during each experimental intervention. In the CTRL group, total force torque decreased from Pretest to Retention and from Posttest to Retention. By contrast, there was an increase between Posttest and Retention in both MI + LFS and MI groups (both ηP2 = 0.03, p < 0.05). Regression analyses further revealed a negative relationship between force performance and EEG activity in the MI + LFS group only. The data support a transient interference of LFS on cortical activity underlying the priming effects of MI practice on force performance. Findings are discussed in relation to the potential for motor reprogramming through MI combined with LFS.

Assessment of arthrogenic quadriceps muscle inhibition by physical examination in the supine position during isometric contraction is feasible as demonstrated by electromyography: a cross-sectional study

BACKGROUND

Preventing severe arthrogenic muscle inhibition (AMI) after knee injury is critical for better prognosis. The novel Sonnery-Cottet classification of AMI enables the evaluation of AMI severity but requires validation. This study aimed to investigate the electromyography (EMG) patterns of leg muscles in the examination position from the classification during isometric contraction to confirm its validity. We hypothesised that the AMI pattern, which is characterised by quadriceps inhibition and hamstring hypercontraction, would be detectable in the supine position during isometric contraction.

METHODS

Patients with meniscal or knee ligament injuries were enrolled between August 2023 and May 2024. Surface EMG was assessed during submaximal voluntary isometric contractions (sMVIC) at 0° extension in the supine position for the vastus medialis (VM) and vastus lateralis (VL) muscles and at 20° flexion in the prone position for the semitendinosus (ST) and biceps femoris (BF) muscles. Reference values for normalisation were obtained from the EMG activity during the gait of the uninjured leg. The Kruskal-Wallis test was used to compare the activation patterns of the muscle groups within the same leg, and the post-hoc tests were conducted using the Mann-Whitney U test and Bonferroni correction.

RESULTS

Electromyographic data of 40 patients with knee injuries were analyzed. During sMVIC, the extensor and flexor muscles of the injured leg showed distinct behaviours (P < 0.001), whereas the uninjured side did not (P = 0.144). In the injured leg, the VM differed significantly from the ST (P = 0.018), and the VL differed significantly from the ST and BF (P = 0.001 and P = 0.026, respectively). However, there were no statistically significant differences within the extensor muscle groups (VM and VL, P = 0.487) or flexor muscle groups (ST and BF, P = 0.377).

CONCLUSION

AMI was detectable in the examination position suggested by the Sonnery-Cottet classification. The flexor and extensor muscles of the injured leg exhibited distinct activation behaviours, with inhibition predominantly occurring in the quadriceps muscles, whereas the hamstrings showed excitation.

MRI sequences at different degrees of flexion to investigate knee popping: an unusual way to diagnose an isolated pigmented villonodular synovitis lesion

Knee popping is a frequent symptom among knee disorders which requires further investigation in case of a recent evolution of the symptom or pathological associated ones. This article reports a rare presentation of pigmented villonodular synovitis (PVNS), identified as the cause of knee popping symptoms, by performing MRI sequences at various degrees of knee flexion for a patient complaining from a gradual onset of knee popping, occurring when bending the knee over 120° of flexion. MRI sequences were performed just before the popping occurs (flexion 90°) and right after it had occurred (flexion 120°). The latter confirmed the origin of the symptom as the lesion moved forward, passing brutally through the interstice between the PCL and the ACL at 120° of flexion, explaining the popping. Treatment decision was to perform an arthroscopic resection of the lesion. Diagnosis of isolated PVNS was confirmed after anatomopathological analysis.

Quadriceps Activation After Anterior Cruciate Ligament Reconstruction: The Early Bird Gets the Worm!

Arthrogenic Muscle Inhibition (AMI) is a phenomenon observed in individuals with joint injury or pathology, characterized by a reflexive inhibition of surrounding musculature, altered neuromuscular control, and compromised functional performance. After anterior cruciate ligament reconstruction (ACLR) one of the most obvious consequences of AMI is the lack of quadriceps activation and strength. Understanding the underlying mechanisms of AMI is crucial for developing effective therapeutic interventions. The surgical procedure needed to reconstruct the ACL has biochemical et physiological consequences such as inflammation, pain, and altered proprioception. These alterations contribute to the development of AMI. Therapeutic interventions aimed at addressing AMI encompass a multidimensional approach targeting pain reduction, inflammation management, proprioceptive training, and quadriceps activation. Early management focusing on pain modulation through modalities like ice, compression, and pharmacological agents help mitigate the inflammatory response and alleviate pain, thereby reducing the reflexive inhibition of quadriceps. Quadriceps activation techniques such as neuromuscular electrical stimulation (NMES) and biofeedback training aid in overcoming muscle inhibition and restoring muscle strength. NMES elicits muscle contractions through electrical stimulation, bypassing the inhibitory mechanisms associated with AMI, thus facilitating muscle activation and strength gains. Comprehensive rehabilitation programs tailored to individual needs and stage of recovery are essential for optimizing outcomes in AMI. The objective of this clinical viewpoint is to delineate the significance of adopting a multimodal approach for the effective management of AMI, emphasizing the integration of pain modulation, proprioceptive training, muscle activation techniques, and manual therapy interventions. Highlighting the critical role of early intervention and targeted rehabilitation programs, this article aims to underscore their importance in restoring optimal function and mitigating long-term complications associated with AMI.

Ultrasound-guided gluteal nerves electrical stimulation to enhance strength and power in individuals with chronic knee pain: a randomized controlled pilot trial

Introduction

Various pathophysiological contexts can be accompanied by weakness, arthrogenic muscle inhibition, and even disability. In this scenario, peripheral nerve stimulation has been studied not only for pain management but also for the improvement of neuromuscular parameters. For this purpose, the use of Transcutaneous Electrical Nerve Stimulation (TENS) has typically been investigated, but recently, the use of ultrasound-guided percutaneous peripheral nerve stimulation (pPNS) has gained popularity. In this regard, electrical stimulation has a predisposition to activate Type II muscle fibers and has been shown to be capable of generating short-term potentiation by increasing calcium sensitivity. However, the evidence of pPNS applied in humans investigating such variables is rather limited.

Objectives

This pilot study aimed to assess the feasibility of the methodology and explore the potential of pPNS in enhancing hip extension performance in individuals suffering from knee pain, comparing it with TENS.

Methods

Twelve participants were divided into pPNS and TENS groups, undergoing pre- and post-intervention assessments of peak concentric power (W), strength (N), execution speed (m/s), and one-repetition maximum (1RM) (kg) estimation. For pPNS, two needles were positioned adjacent to the superior and inferior gluteal nerves under ultrasound guidance. For TENS, electrodes were positioned between the posterosuperior iliac spine and the ischial tuberosity, and halfway between the posterosuperior iliac spine and the greater trochanter. The interventions consisted of 10 stimulations of 10 s at a frequency of 10 Hz with a pulse width of 240 μs, with rest intervals of 10 s between stimulations.

Results

Peripheral nerve stimulation significantly improved concentric power at 30% (p = 0.03) and 50% (p = 0.03) of 1RM, surpassing TENS, which showed minimal changes. No significant strength differences were observed post-intervention in either group.

Conclusion

This work presents evidence where pPNS applied to the gluteal nerves results in an enhanced performance of hip extension at submaximal loads. However, this improvement does not seem to be reflected in short-term changes in the estimation of the 1RM by the force-velocity profile.

Rehabilitation and Return to Sport After Anterior Cruciate Ligament Reconstruction

Rehabilitation after an anterior cruciate ligament (ACL) reconstruction requires patience, devotion, and discipline. Rehabilitation should be individualized to each patient's specific need and sport. Return to sport is a continuum throughout the rehabilitation, and patients should not return to performance before passing a battery of muscle function tests and patient-reported outcomes, as well as change of direction-specific tests. Return to full participation should be an agreement between the patient, physical therapist, surgeon, and coach. For minimal risk for second ACL injury, patients should continue with maintenance and prevention training even after returning to sport.

How Biofeedback With Surface EMG Can Contribute to the Diagnosis and Treatment of AMI in the Knee

Background

Arthrogenic muscle inhibition (AMI) is a complex neurological phenomenon that is actually very common. AMI can appear following a knee injury or knee surgery. If it is not addressed, the patient's function can be negatively affected. There is currently no specific tool for the diagnosis and treatment of AMI.

Indications

Following surgery or injury to the knee, AMI causes defective activation of the quadriceps, sometimes combined with a knee extension deficit. A clinical classification of AMI has been proposed recently to help with making the diagnosis and to guide treatment. In this article, we describe how biofeedback and surface electromyography (EMG) can be used in the early diagnosis and treatment of knee AMI.

Technique Description

Biofeedback is based on transformation of physiological variables into a visual or auditory signal. This allows the patient to learn how to control physical and bodily functions, which were previously considered as involuntary processes. This technique requires the use of a specific device that transforms the measured physiological signals-neuromuscular activation in this instance-into visual signals. This tool incorporates surface EMG, with electrodes connected to a measuring unit. This unit is connected to a screen that shows the neuromuscular activation in real time. Thus, EMG biofeedback can be used to help clinicians make a diagnosis and to specifically treat the AMI.

Results

We have used biofeedback in patients who have a knee injury or who have undergone knee surgery. Both the therapist and patient were able to objectively see the presence of AMI using the biofeedback device. For treatment, the therapist works with a patient by providing clear instructions and increasingly more challenging goals. We show examples of how patients were able to eliminate their AMI by using biofeedback.

Discussion/Conclusion

EMG biofeedback is a promising tool for the diagnosis and treatment of AMI after an anterior cruciate ligament (ACL) tear and ACL reconstruction surgery. The next steps are to define thresholds and a rehabilitation protocol that will be used in a clinical trial.

Patient Consent Disclosure Statement

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Effect of open vs. closed kinetic chain exercises in ACL rehabilitation on knee joint pain, laxity, extensor muscles strength, and function: a systematic review with meta-analysis

Anterior cruciate ligament (ACL) injuries are common among physically active individuals, often requiring ACL reconstruction (ACLR) for recovery. Rehabilitating these injuries involves determining the appropriate timing for initiating open kinetic chain (OKC) exercises. Although OKC exercises are effective post-ACLR, their use in rehabilitation remains a subject of debate. Therefore, this study aims to conduct a systematic review to determine whether OKC or closed kinetic chain (CKC) exercises result in differences in laxity, strength of the knee extensor muscle group, function, and functional performance in ACL rehabilitation. Five electronic databases were searched for randomized controlled between-group trials (RCTs). Two reviewers independently evaluated the risk of bias using the PEDro scale. We performed a meta-analysis using a random-effects model or calculated mean differences (fixed-effect) where appropriate. Certainty of evidence was judged using the GRADE approach. The systematic literature search yielded 480 articles, of which 9 met the inclusion criteria. The evidence for all outcomes ranged from very low to low certainty. Across all comparisons, inconsistent results were found in outcome measures related to knee function between OKC and CKC exercises post-ACLR. A significant increase in quadriceps isokinetic strength was found in post-ACLR and ACL-deficient knees in favor of OKC exercises at 3 (p = 0.03) and 4 (p = 0.008) months, respectively. A significant decrease in knee laxity was observed in ACL-deficient knees in favor of OKC at 10 weeks (p = 0.01), although inconsistency was noted at 4 months. Finally, a significant decrease in pain was found in favor of early OKC compared to late OKC (p < 0.003). Additionally, in ACL-deficient knees, low load resistance training (LLRT) OKC showed no significant laxity difference compared to controls (p > 0.05). In contrast, high load resistance training (HLRT) OKC had less laxity than controls at 6 weeks (p = 0.02) but not at 12 weeks (p > 0.05). OKC exercises appear to be superior to CKC for improving quadriceps strength 3-4 months post-injury, whether as a part of conservative or post-surgery rehabilitation. On the other hand, OKC exercises seem to be either superior or equally effective to CKC for improving knee laxity, thus presenting their importance in being included in a rehabilitation protocol from the initial phase.

Systematic Review Registration

PROSPERO [CRD42023475230].

Use of electromyographic biofeedback in rehabilitation following anterior cruciate ligament reconstruction: a systematic review and meta-analysis

BACKGROUND

Rehabilitation following anterior cruciate ligament (ACL) reconstruction surgery is essential to regain functionality and return to previous activity level. Electromyographic biofeedback may be an effective intervention for rehabilitation of patients following ACL surgery.

OBJECTIVE

To synthesize the available evidence on the effect of electromyographic biofeedback in the treatment of quadriceps strength following ACL surgery.

DESIGN

Systematic review with meta-analysis.

DATA SOURCES

PubMed, EMBASE, CENTRAL and Epistemonikos were searched.

ELIGIBILITY CRITERIA

Randomized clinical trials with patients undergoing ACL reconstruction surgery comparing biofeedback with a standard rehabilitation control group.

DATA EXTRACTION AND DATA SYNTHESIS

Two authors selected articles and performed data extraction. The analysed outcomes were strength, function, pain, knee extension and balance. The risk of bias of individual studies was assessed using the Cochrane Risk of Bias Tool. Results were combined through random-effects meta-analysis, reporting mean differences.

RESULTS

Eight articles were included in the qualitative analysis, and four articles were included in the quantitative analysis. The interventions lasted between 4 and 12 weeks. Three studies evaluated the effect of biofeedback on quadriceps strength; of these, two studies showed a significant difference in favour of the biofeedback group. In addition, biofeedback was found to improve knee extension [standardized mean difference - 1.3, 95% confidence interval (CI) - 1.74 to -0.86] and balance (one study). There was no significant difference in Lysholm score (mean difference -6.21, 95% CI -17.51 to 5.08; I2 =59%) or pain between the biofeedback group and the control group.

CONCLUSION

Electromyographic biofeedback in knee rehabilitation could be useful following ACL reconstruction surgery.

KEY MESSAGES

SYSTEMATIC REVIEW REGISTRATION NUMBER: PROSPERO (CRD42020193768).

Nurse-Assisted Rehabilitation Protocols Following Anterior Cruciate Ligament Reconstruction

Despite significant advancements in surgical instruments and operation skills, short- and long-term outcomes following anterior cruciate ligament reconstruction (ACLR) remain unsatisfactory, as many patients fail to return to their pre-injury level of sports. Inadequate ACL rehabilitation is the primary cause of poor outcomes. Nurses have become a crucial element in the rehabilitation process. Although there is no consensus regarding the optimal post-operative rehabilitation protocols, restoring muscle strength and neuromuscular control are consistently the primary goals. This literature review presents nurse-assisted rehabilitation protocols aiming at improving muscle strength and neuromuscular control. The review discusses postoperative rehabilitation, including home-based and supervised rehabilitation, open and closed kinetic chain exercises, eccentric and concentric training, blood flow restriction training, and plyometric training. Each training protocol has its benefits and drawbacks, and should be used cautiously in specific stages of rehabilitation. Neuromuscular training, such as neuromuscular electrical stimulation, neuromuscular control exercises, and vibration therapy, is considered crucial in rehabilitation.

Neuromotor Treatment of Arthrogenic Muscle Inhibition After Knee Injury or Surgery

BACKGROUND

Persistent weakness of the quadriceps muscles and extension deficit after knee injuries are due to specific alterations in neural excitability - a process known as arthrogenic muscle inhibition (AMI). The effects of a novel neuromotor reprogramming (NR) treatment based on the use of proprioceptive sensations associated with motor imagery and low frequency sounds have not been studied in AMI after knee injuries.

HYPOTHESIS

This study aimed to assess quadriceps electromyographic (EMG) activity and the effects on extension deficits in persons with AMI who completed 1 session of NR treatment. We hypothesized that the NR session would activate the quadriceps and improve extension deficits.

STUDY DESIGN

Case series.

LEVEL OF EVIDENCE

Level 4.

METHODS

Between May 1, 2021 and February 28, 2022, patients who underwent knee ligament surgery or sustained a knee sprain with a deficit of >30% of the vastus medialis oblique (VMO) on EMG testing in comparison with the contralateral limb after their initial rehabilitation were included in the study. The maximal voluntary isometric contraction of the VMO measured on EMG, the knee extension deficit (distance between the heel and the table during contraction), and the simple knee value (SKV) were assessed before and immediately after completion of 1 session of NR treatment.

RESULTS

A total of 30 patients with a mean age of 34.6 ± 10.1 years (range, 14-50 years) were included in the study. After the NR session, VMO activation increased significantly, with a mean increase of 45% (P < 0.01). Similarly, the knee extension deficit significantly improved from 4.03 ± 0.69 cm before the treatment to 1.93 ± 0.68 after the treatment (P < 0.01). The SKV was 50 ± 5.43% before the treatment, and this increased to 67.5 ± 4.09% after the treatment (P < 0.01).

CONCLUSION

Our study indicates that this innovative NR method can improve VMO activation and extension deficits in patients with AMI. Therefore, this method could be considered a safe and reliable treatment modality in patients with AMI after knee injury or surgery.

CLINICAL RELEVANCE

This multidisciplinary treatment modality for AMI can enhance outcomes through the restoration of quadriceps neuromuscular function and subsequent reduction of extension deficits after knee trauma.

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.

Intrinsic graft laxity variation with open kinetic chain exercise after anterior cruciate ligament reconstruction: A non-randomized controlled study

OBJECTIVES

To determine whether quadriceps and hamstring strengthening in a rehabilitation program involving early open kinetic chain (OKC) and/or closed kinetic chain (CKC) knee joint exercises had an influence on graft laxity at 1, 3, and 6 months after anterior cruciate ligament reconstruction (ACLR).

DESIGN

Retrospective study.

METHODS

Two groups (n = 53) of ACLR patients (combination of OKC and CKC exercises group compared to a CKC exercise group) were recruited. OKC protocol was introduced at 2 weeks post-operatively without external resistance and progressed at 4 weeks with load. Comparative ACL graft laxity measurement and isokinetic strength testing were prospectively performed up to 6 months in both groups.

RESULTS

No significant differences were observed in the knee laxity at 1 (p = 0.263), 3 (p = 0.263), and 6 months (p = 0.256) follow up between the groups. Similarly, no significant results were observed in within-group knee laxity between 1 and 6 months after ACLR in the intervention (p = 0.155) and control group (p = 0.690).

CONCLUSION

The early initiation of OKC along with CKC exercises doesn't seem to increase the ACLR graft laxity as compared to a rehabilitation program with only CKC exercises.

Exercise combined with electrical stimulation for the treatment of chronic ankle instability - A randomized controlled trial

PURPOSE

To compare the short, medium, and long-term effects of balance exercises combined with either peroneal neuromuscular electrical stimulation (NMES) or peroneal transcutaneous electrical nerve stimulation (TENS) on dynamic postural control and patient reported outcome measures (PROMs) in patients with chronic ankle instability (CAI).

METHODS

Thirty-four participants with CAI were randomly assigned to a 12-session home based exercise program combined with NMES (Ex-NMES) or TENS (Ex- TENS). Baseline postural control was tested with the modified Star Excursion Balance Test (mSEBT) and time to stabilization (TTS) after a single-leg drop-jump. The self-reported function was measured using the Cumberland Ankle Instability Tool (CAIT), the Identification of Functional Ankle Instability (IdFAI), and the Sports subscale of the Foot and Ankle Ability Measure (FAAMSport).

RESULTS

Both groups showed significant improvements in all self-reported outcome measures at the 12-month follow-up. Subjects in the Ex-NMES group had significantly better IdFAI (-4.2 [95% CI -8.1, -0.2]) and FAAMSport (13.7 [95% CI 2.2, 25.2]) scores at 6- and 12-month follow-up, respectively, compared to the Ex-TENS group. Medium to large between-group effect sizes were observed in self-reported functional outcomes and the mSEBT.

CONCLUSION

The consistent trend of improvement in self-reported functional outcomes when training is combined with NMES compared with training with TENS may indicate a potential benefit that should be further investigated as a treatment for patients with CAI.

Prevention of knee stiffness following ligament reconstruction: Understanding the role of Arthrogenic Muscle Inhibition (AMI)

The knee is a joint that is often injured in sport, with a large and increasing number of ligament tears and repairs; postoperative complications can lead to poor outcome, such as stiffness. Beyond the well-known and well-described intra- and extra-articular causes of postoperative stiffness, the present study introduces the concept of a central reflex motor inhibition mechanism called arthrogenic muscle inhibition (AMI). AMI occurs after trauma and can be defined as active knee extension deficit due to central impairment of Vastus Medialis Obliquus (VMO) contraction, often associated with spinal reflex hamstring contracture. This explains the post-traumatic flexion contracture that is so common after knee sprain. The clinical presentation of AMI is easy to detect in consultation, in 4 grades from simple VMO inhibition to fixed flexion contracture by posterior capsule retraction in chronic cases. After recent anterior cruciate ligament (ACL) tear, more than 55% of patients show AMI, reducible in 80% of cases by simple targeted exercises initiated in consultation. Practically, in patients who have sustained knee sprain, it is essential to screen for this reflex mechanism and assess reducibility, as AMI greatly aggravates the risk of postoperative stiffness. In case of hemarthrosis, we recommend joint aspiration, which provides immediate benefit in terms of pain and motor inhibition. In case of persistent AMI, classical electrostimulation and "cushion crush", as used by all physiotherapists, are ineffective. To reduce the risk of postoperative stiffness, no surgery should be considered until AMI has resolved. LEVEL OF EVIDENCE: expert opinion.

What interventions can treat arthrogenic muscle inhibition in patients with chronic ankle instability? A systematic review with meta-analysis

PURPOSE

To identify, critically appraise, and synthesize the existing evidence regarding the effects of therapeutic interventions on arthrogenic muscle inhibition (AMI) in patients with chronic ankle instability (CAI).

MATERIALS AND METHODS

Two reviewers independently performed exhaustive database searches in Web of Science, PubMed, Medline, CINAHL, and SPORTDiscus.

RESULTS

Nine studies were finally included. Five types of disinhibitory interventions were identified: focal ankle joint cooling (FAJC), manual therapy, fibular reposition taping (FRT), whole-body vibration (WBV), and transcranial direct current stimulation (tDCS). There were moderate effects of FAJC on spinal excitability in ankle muscles (g = 0.55, 95% CI = 0.03-1.08, p = 0.040 for the soleus and g = 0.54, 95% CI = 0.01-1.07, p = 0.046 for the fibularis longus). In contrast, manual therapy, FRT, WBV were not effective. Finally, 4 weeks of tDCS combined with eccentric exercise showed large effects on corticospinal excitability in 2 weeks after the intervention (g = 0.99, 95% CI = 0.14-1.85 for the fibularis longus and g = 1.02, 95% CI = 0.16-1.87 for the tibialis anterior).

CONCLUSIONS

FAJC and tDCS may be effective in counteracting AMI. However, the current evidence of mainly short-term studies to support the use of disinhibitory interventions is too limited to draw definitive conclusions.

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

BACKGROUND

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

PURPOSE

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

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

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

RESULTS

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

CONCLUSION

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

Multifidus dysfunction and restorative neurostimulation: a scoping review

OBJECTIVE

Chronic low back pain (CLBP) is multifactorial in nature, with recent research highlighting the role of multifidus dysfunction in a subset of nonspecific CLBP. This review aimed to provide a foundational reference that elucidates the pathophysiological cascade of multifidus dysfunction, how it contrasts with other CLBP etiologies and the role of restorative neurostimulation.

METHODS

A scoping review of the literature.

RESULTS

In total, 194 articles were included, and findings were presented to highlight emerging principles related to multifidus dysfunction and restorative neurostimulation. Multifidus dysfunction is diagnosed by a history of mechanical, axial, nociceptive CLBP and exam demonstrating functional lumbar instability, which differs from other structural etiologies. Diagnostic images may be used to grade multifidus atrophy and assess other structural pathologies. While various treatments exist for CLBP, restorative neurostimulation distinguishes itself from traditional neurostimulation in a way that treats a different etiology, targets a different anatomical site, and has a distinctive mechanism of action.

CONCLUSIONS

Multifidus dysfunction has been proposed to result from loss of neuromuscular control, which may manifest clinically as muscle inhibition resulting in altered movement patterns. Over time, this cycle may result in potential atrophy, degeneration and CLBP. Restorative neurostimulation, a novel implantable neurostimulator system, stimulates the efferent lumbar medial branch nerve to elicit repetitive multifidus contractions. This intervention aims to interrupt the cycle of dysfunction and normalize multifidus activity incrementally, potentially restoring neuromuscular control. Restorative neurostimulation has been shown to reduce pain and disability in CLBP, improve quality of life and reduce health care expenditures.

Clinical Utility of Ultrasound Imaging for Measuring Anterior Thigh Thickness after Anterior Cruciate Ligament Injury in an Individual Patient to Assess Postsurgery Outcome

The present study investigated the clinical utility of ultrasound imaging (USI) for assessing changes in an individual's quadriceps muscle and subcutaneous fat (SF) thickness of the anterior thigh and their relative proportions. A patient was studied prior to and after anterior cruciate ligament reconstruction (ACLR) surgery and during rehabilitation. This case study involved an 18-year-old female recreational athlete with a complete tear of the anterior cruciate ligament (ACL). Tissue thickness (SF and quadriceps muscle) was measured from transverse USI of the anterior thigh before surgery, at weekly intervals during 12 weeks of postsurgery, and then every 2 weeks for the following 12 weeks (total of 21 measurement sets). Statistically significant differences presurgery to postrehabilitation were found for muscle thickness (p = 0.04) and SF tissue thickness (p = 0.04) measurements. There was no difference in muscle to fat ratio (p = 0.08). Changes in measurements greater than the reported minimal detectable change (MDC) demonstrate the sensitivity of the USI technique as an objective tool to assess clinically useful changes in an individual's anterior thigh muscle thickness post-ACLR surgery and during rehabilitation.

Effectiveness of a theory-driven mHealth intervention in promoting post-surgery rehabilitation adherence in patients who had anterior cruciate ligament reconstruction: A randomized clinical trial

RATIONALE

Patients with anterior cruciate ligament (ACL) reconstruction often have poor adherence to post-surgery rehabilitation.

OBJECTIVE

This study applied the integrated model of self-determination theory and the theory of planned behavior to examine the effects of a smartphone-delivered intervention on the recovery outcomes of patients with an ACL rupture during post-surgery rehabilitation period. Additionally, we explored the effects of the intervention on participants with different beliefs toward rehabilitation at baseline.

METHODS

The randomized control trial recruited 96 eligible participants (M age = 27.82 years, SD = 8.73; female = 39%) who underwent ACL reconstruction surgery. Participants were randomly assigned to an intervention group (n = 41), which received standard post-surgical treatment (usual-care) and smartphone application ("ACL-Well"), or a usual-care control group (n = 55). The primary outcomes were recovery outcomes from ACL surgery measured by knee muscle strength and laxity, and subjective knee evaluation completed 4-month post-intervention. Secondary outcomes were the psychological and behavioral outcomes measured at baseline, at 2- and 4-month post-intervention.

RESULTS

ANCOVA indicated no significant between-group differences in primary outcomes: knee muscle strength, knee laxity and subjective knee evaluation, Fs(1, 27 to 55) = 0.01 to 1.36, p = .25 to .99, η2 = 0.01 to 0.03. For the secondary outcomes, growth mixture modelling revealed self-determined treatment motivation declined significantly over the intervention period in the control group (M slope = -0.39 to -0.12, p = .01 to .04), but not in the intervention group (M slope = -0.19 to -0.08, p = .06 to .38).

CONCLUSIONS

The smartphone application fell short in promoting orthopedic outpatients' recovery outcomes. Yet, it shows some promises as a mean to maintain patients' motivation and adherence to treatment.

Risk Factors for Symptomatic Cyclops Lesion Formation after Anterior Cruciate Ligament Reconstruction

Objective  To evaluate the incidence of symptomatic cyclops lesions requiring surgical treatment after anterior cruciate ligament (ACL) reconstruction and to establish possible intraoperative risk factors related to it. Methods  Three hundred and eighty-nine patients aged between 18 and 50 years who underwent primary ACL reconstruction were retrospectively evaluated. Patients were divided into groups according to the presence or absence of symptomatic cyclops lesions, and their characteristics were compared. Patients with associated lesions that required additional surgical procedures (except anterolateral extra-articular procedures) were not included. The rate of symptomatic cyclops lesions was recorded and the following parameters were evaluated: age, gender, time from injury to surgery, graft type and diameter, femoral tunnel perforation technique, fixation type, presence of knee hyperextension, preservation of the ACL remnant, associated anterolateral extra-articular procedure, associated meniscal injury and participation in sports. Results  389 patients were evaluated and 26 (6.7%) patients developed cyclops. The patients with and without cyclops lesions did not differ in age, time from injury to surgery, graft type or diameter, surgical technique, femoral fixation method, presence of knee hyperextension, remnant preservation and associated meniscal injury. The group with cyclops lesion had a higher proportion of females (10 (38.4%) vs 68 (18.7%); OR = 2.7; p  = 0.015), higher proportion of extra-articular reconstruction (18 (11.8%) vs 8 (3.4%); OR = 3.8; p  = 0.001) and higher proportion of sports practice (23 (8.6%) vs 3 (2.5%); OR = 3.6; p  = 0.026). Conclusion  In our series, 6.7% of the patients required arthroscopic removal of cyclops lesions. Female gender, associated extra-articular reconstruction and sports practice were factors related to this lesion. Remnant preservation had no relationship with cyclops lesion formation.

Muscle Strength and Efficiency of Muscle Activities Recovery Using Single-Joint Type Hybrid Assistive Limb in Knee Rehabilitation after Anterior Cruciate Ligament Reconstruction

Decreased muscle strength often occurs after anterior cruciate ligament (ACL) reconstruction; this can include muscle atrophy, neuromuscular dysfunction, and reduced force generation efficiency. Hybrid assistive limb (HAL) technology, which integrates an interactive biofeedback system connecting the musculoskeletal system to the brain and spinal motor nerves, offers a potential intervention. Our study, conducted from March 2018 to August 2023 using knee HAL single-joint technology, was a prospective non-randomized controlled trial involving 27 patients who had undergone arthroscopic ACL reconstruction. They were split into two groups: HAL (18 patients) and control (nine patients). Beginning 18 weeks after their surgery, the HAL group participated in three weekly sessions of knee HAL-assisted exercises. Both the HAL and control groups underwent isokinetic muscle strength tests at postoperative weeks 17 and 21. Testing utilized an isokinetic dynamometer at 60°/s, 180°/s, and 300°/s. The Limb Symmetry Index (LSI) was employed to measure side-to-side differences. The HAL group showed significant LSI improvements in peak extension torque across all testing velocities and for peak flexion torque at 60°/s and 300°/s. The rate of change in LSI for peak flexion torque at 300°/s was significantly higher post-measurements (p = 0.036; effect size = 1.089). The change rate for LSI in peak extension torque at 300°/s and all peak flexion torques showed medium to large effect sizes in Cohen's d. In conclusion, knee HAL single-joint training positively influenced muscle strength recovery and efficiency. The HAL training group exhibited superior muscle strength at various isokinetic testing velocities compared to the control group.

Early ACL reconstruction shows an improved recovery of isokinetic thigh muscle strength compared to delayed or chronic cases

INTRODUCTION

The recovery of periarticular strength is a major criterion in return-to-play testing. The rationale of the study was to assess the impact of the delay of surgery (∆ between injury and surgery) on knee extensor and knee flexor strength of anterior cruciate ligament (ACL)-deficient patients six months after reconstruction.

MATERIALS AND METHODS

In a retrospective cohort study, all patients with ACL ruptures between 03/2015 and 12/2019 were analyzed. Inclusion criteria were isolated ACL rupture without any associated lesions undergoing a reconstruction using ipsilateral hamstring tendon autograft and adherence to isokinetic strength testing before and at 5-7 months postoperatively. These patients were then clustered into three groups: EARLY reconstruction (∆ < 42 days), DELAYED reconstruction (∆42-180d), and CHRONIC (∆ > 180d). Knee extensor and flexor strength of the ipsi- and contralateral leg were analyzed by concentric isokinetic measurement (60°/s). Primary outcomes were the maximal knee extension and flexion torque, hamstrings-to-quadriceps ratio (H/Q) ratio), and the corresponding limb symmetry indices.

RESULTS

n = 444 patients met the inclusion criteria. From EARLY to DELAYED to CHRONIC, a progressive reduction in postoperative strength performance was observed in knee extension (1.65 ± 0.45 to 1.62 ± 0.52 to 1.51 ± 0.5 Nm/kg resp.) and flexion (1.22 ± 0.29 to 1.18 ± 0.3 to 1.13 ± 0.31 Nm/kg resp.) strength on the ACL reconstructed leg. This general loss in periarticular strength was already apparent in the preoperative performance even on the healthy side. When controlling for the preoperative performance using ANCOVA analysis, EARLY performed significantly better than DELAYED (extension p = 0.001, flexion p = .02) and CHRONIC (extension p = 0.005, flexion p < 0.001). Also, there were significantly higher values for H/Q ratio in the injured leg across all groups where the H/Q ratio increased from EARLY to CHRONIC and from pre- to postoperative values.

CONCLUSIONS

With respect to the force generating capacity when returning-to-play, it is advantageous to seek for an early ACL reconstruction within the first 12 weeks after the injury. The increasing loss of thigh muscle strength observed in delayed or chronic cases affects the injured and also the non-injured leg.

LEVEL OF EVIDENCE

III, retrospective cohort study.

Persistence of neuromuscular activation deficit in the lower limb at 3-years of follow-up after ACL reconstruction surgery

BACKGROUND

Almost all patients experience neuromuscular disorders of the quadriceps after knee trauma or surgery such as anterior cruciate ligament (ACL) reconstruction. This phenomenon is described in literature as arthrogenic muscle inhibition (AMI). It can be detrimental to patients and cause complications. However, few studies have evaluated the long-term persistence of deficits arising from this, following ACL reconstruction.

PURPOSE

By comparing neuromuscular activation in the lower limb after ACL reconstruction with the unaffected lower limb, after more than 3-years of follow-up, this study aimed to evaluate the possible persistence of long-term deficits after surgery.

METHODS

Fifty-one patients who underwent ACL reconstruction in 2018 were included in the study, with a minimum follow-up of 3 years. The neuromuscular activation deficit was assessed using the Biarritz Activation Score-Knee (BAS-K), whose intra- and inter-observer reproducibility was also evaluated. The ACL-RSI, KOOS, SANE Leg, Tegner and IKDC scores were also evaluated.

RESULTS

The mean BAS-K score of the knee that underwent surgery was 21.8/50 versus 37.9/50 in the healthy knee (p < 0.05). The SANE leg score was 76.8/100 versus 97.6/100 (p < 0.05). The mean IKDC was 84.17 (±12.7). The mean KOOS was 86.2 (±9.2). The mean ACL-RSI was 70 (±7.9) and the Tegner score was 6.3 (±1.2). Intra- and inter-observer reproducibility was satisfactory for the BAS-K score.

CONCLUSION

We found that the neuromuscular activation deficit was high (roughly 42%) at more than 3-years of follow-up after ACL reconstruction. The deficit is not limited to the quadriceps and affects the whole limb. Our findings highlight the need for appropriate rehabilitation after ACL surgery, targeting the corticospinal level in particular.

LEVEL OF EVIDENCE III

prognostic retrospective case-control study.

Dynamic intermittent compression cryotherapy with intravenous nefopam results in faster pain recovery than static compression cryotherapy with oral nefopam: post-anterior cruciate ligament reconstruction

PURPOSE

To evaluate the effectiveness of dynamic intermittent compression cryotherapy (DICC) (CryoNov®) with an intravenous nefopam-based pain management protocol (DCIVNPP) in reducing post-operative pain following anterior cruciate ligament reconstruction (ACLR) compared to static compression cryotherapy (SCC) (Igloo®) and oral Nefopam.

METHODS

This was a retrospective analysis of prospectively collected data including 676 patients who underwent primary ACLR in 2022. Patients were either in the DCIVNPP group or in the SCC (control group), and were matched for age, sex, and Lysholm and Tegner scores (338 per arm). The primary outcome was pain on the visual analogue scale (VAS), analyzed in relation to the minimal clinically important difference (MCID) and the Patient Acceptable Symptom State (PASS) thresholds for VAS. The secondary outcome was side effects.

RESULTS

Postoperative pain in the DCIVNPP group was less severe on the VAS than in the control group (p < 0.05). The maximum difference in the VAS between groups was 0.57, which is less than the MCID threshold for VAS. The DCIVNPP group crossed the PASS threshold for VAS on Day 3, sooner than the control group. The side effect profiles were similar in both groups except for higher rates of dizziness and malaise in the DCIVNPP group, and higher rates of abdominal pain in the control group. Most of the side effects decreased over time in both groups, with no significant side effects after Day 3.

CONCLUSION

DCIVNPP effectively allows for faster pain recovery than in the control group. The difference in side effects between the protocols may be due to mode of administration of nefopam.

LEVEL OF EVIDENCE

III.

What Are the Criteria for an Acute Form of Anterior Cruciate Ligament Tear for the Severity of the Process by Gait Analysis Data?

PURPOSE

There is still controversy over the criteria for acute ACL tear. In this paper, knee joint function and walking were considered possible ones.

METHOD

The study included 21 subjects with acute ACL tear and 20 healthy volunteers as a control group. Biomechanical gait analysis was performed using the inertial sensor system including EMG recording. All subjects (but for controls) were divided into two groups: Group 1-"up to 4 weeks" and Group 2-"from 4 weeks to 3 months".

RESULTS

Temporal gait parameters in subjects from Group 1 demonstrate the asymmetry of 4% and more in terms of the gait cycle with a decrease in the affected limb, and are within normal range in Group 2. The amplitudes at the hip and knee joints in the affected limb are reduced which is especially pronounced in Group 1 (2-4 and 6-10 degrees, respectively). The affected knee joint shows a decrease in the range of motion by up to 5 degrees in the first half of the stance phase and flexion by less than 40 degrees in the swing phase. The tibialis anterior and quadriceps femoris muscle function is decreased in the affected limb only in Group 1 (72% and 78% from normal, respectively).

CONCLUSIONS

The severity of the condition after an ACL tear is largely determined by functional changes. The time factor is of secondary importance.

Altered Knee Loading Following Primary ACL Repair versus ACL Reconstruction

Background

ACL repair (ACL-r) has recently gained renewed clinical interest for treatment of ACL tears. ACL-r has several potential benefits over ACL reconstruction (ACL-R) including maintaining the native ACL innervation and blood supply, no graft site morbidity, and possible improved knee biomechanics and decrease in osteoarthritis. The purpose of this study was to assess for differences in metrics of knee joint loading during a single limb squat task between individuals following a primary ACL-r versus those who underwent a standard ACL-R with a patella bone-tendon-bone autograft.

Study type

Case Control Study.

Methods

The ACL-r group [n: 15, age(yrs): 38.8±13.9] sustained a proximal ACL disruption that was amenable to repair, while the ACL-R group [n: 15, age(yrs): 25.60±1.7] underwent primary reconstruction with patella bone-tendon-bone autograft. At 12-weeks post-operation, both groups completed the IKDC questionnaire and biomechanical testing during performance of the single limb squat. Bilateral peak knee extension moment and total knee joint power as a measure of eccentric loading (contraction) during the descent phase of the squat were calculated on the surgical and non-surgical limb and averaged across the middle three of five trials. Participants also completed quadriceps strength testing on both limbs three months after surgery on an isokinetic dynamometer at 60°/sec. LSI (Limb Strength Index) was calculated for all variables. Separate ANCOVAs were performed on each biomechanical variable to examine differences between groups.

Results

The ACL-r had a significantly greater peak knee extension moment LSI (ACL-r: 78.46±5.79%; ACL-R: 56.86±5.79%; p=0.019, ηp2=.186) and total knee joint power LSI (ACL-r: 72.47±7.39%; ACL-R: 39.70±7.39%, p=0.006, ηp2=.245) than the ACL-R group. The ACL-r also had a significantly greater quadriceps LSI than the ACL-R group (ACL-r: 66.318±4.61%, ACL-R: 48.03±4.61%, p=0.013, ηp2=.206).

Conclusions

Individuals following ACL-r demonstrate increased knee joint loading symmetry during a single leg squat task and greater quadriceps strength symmetry at 12 weeks post-surgery compared to those who underwent ACL-R.

Level of Evidence

3.

Quadriceps Dysfunction Following Joint Preservation Surgery: A Review of the Pathophysiologic Basis and Mitigation Strategies

PURPOSE OF REVIEW

To characterize quadriceps muscle dysfunction associated with knee joint preservation surgery, with a focus on its pathophysiology and promising approaches to mitigate its impact on clinical outcomes.

RECENT FINDINGS

Quadriceps dysfunction (QD) associated with knee joint preservation surgery results from a complex interplay of signaling, related to changes within the joint and from those involving the overlying muscular envelope. Despite intensive rehabilitation regimens, QD may persist for many months postoperatively and negatively impact clinical outcomes associated with various surgical procedures. These facts underscore the need for continued investigation into the potential detrimental effects of regional anesthetic and intraoperative tourniquet use on postoperative quadriceps function, with an outward focus on innovation within the field of postoperative rehabilitation. Neuromuscular stimulation, nutritional supplementation, cryotherapy, blood flow restriction (BFR), and open-chain exercises are all potential additions to postoperative regimens. There is compelling literature to suggest that these modalities are efficacious and may diminish the magnitude and duration of postoperative QD. A clear understanding of QD, with respect to its pathophysiology, should guide perioperative treatment and rehabilitation strategies and influence ongoing rehabilitation-based research and innovation. Moreover, clinicians must appreciate the magnitude of QD's effect on diminished clinical outcomes, risk for re-injury and patients' ability (or inability) to return to pre-injury level of activity following knee joint preservation procedures.