Arthrogenic muscle inhibition and return to sport after arthrofibrosis complicating anterior cruciate ligament surgery

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.

Does the timing of anterior cruciate ligament reconstruction surgery affect flexion contracture formation in rats?

BACKGROUND

Anterior cruciate ligament injuries are commonly treated with ligament reconstruction surgery, but post-operative joint contracture is a major complication. The optimal timing for anterior cruciate ligament reconstruction remains controversial, with some clinical studies suggesting that early surgery may increase the risk of joint contractures, while others have found no such association. To clarify this, we investigated the effects of the timing of reconstruction surgery on contracture formation using a rat model.

METHODS

Anterior cruciate ligament-transected rats were divided into groups based on the timing of reconstruction: immediate, early, and delayed (1, 14, and 28 days after transection, respectively). Some anterior cruciate ligament-transected rats did not receive reconstruction surgery. Untreated rats served as controls. At 56 days after ligament transection, we assessed knee extension range of motion before (including both myogenic and arthrogenic factors) and after myotomy (arthrogenic factor only), as well as fibrotic changes in the joint capsule.

FINDING

Anterior cruciate ligament transection alone significantly decreased range of motion before myotomy, but not after myotomy. In all reconstructed groups, both range of motions before and after myotomy were significantly reduced compared to the control, indicating the induction of arthrogenic contracture by reconstruction surgery. Fibrotic changes in the joint capsule were observed in all reconstructed groups, contributing to arthrogenic contracture formation. However, the timing of reconstruction had no effect on range of motions and fibrotic changes in the joint capsule.

INTERPRETATION

Our findings may help guide clinical decision-making regarding the timing of anterior cruciate ligament reconstruction surgery.

Lower extremity return to sport testing: A systematic review

BACKGROUND

Lower extremity injuries account for an enormous portion of sports medicine cases in the United States each year. Unfortunately, there are no uniform criteria for athletes to complete prior to returning to sport (RTS) following a lower extremity injury. Therefore, the purpose of this systematic review is to review current literature for joint-specific and global lower extremity testing to determine the most valid functional test that can be utilized to reduce the risk of re-injury as athletes RTS.

METHODS

A systematic search of PubMed, PubMed Central, Cochrane Library, OVID, and Embase databases was conducted for studies prior to May 2024 following PRISMA guidelines. ROBINS-I Tool was utilized for the risk of bias assessment.

RESULTS

Of 19,189 studies, 114 (0.6%) studies published prior to May of 2024 met inclusion criteria and were analyzed. Eighty five percent of articles discussed RTS for individuals with knee pathology. Furthermore, 82% specifically analyzed RTS following ACL reconstruction. The most common RTS test was isokinetic dynamometry testing which is seen in 73% of studies. Only 6.2% of studies analyzed RTS for individuals with hip pathology and only two studies analyzed RTS for patients with ankle injuries.

CONCLUSION

Even with the enormous amount of literature that exists regarding ACL injuries and testing there is no standardized criterion for RTS clearance. The suggested test batteries from this review can serve as a framework for future research and validation for joint-specific RTS functional testing.

Enlightenment on Knee Flexors Strength Loss in Cases of Posterior Knee Pain After Anterior Cruciate Ligament Reconstruction

CONTEXT

The persistence and the recurrence of posterior medial knee pain (PKP) after anterior cruciate ligament reconstruction (ACLR) using hamstring tendon graft are often overlooked during rehabilitation.

DESIGN

Cross-sectional observational study.

METHODS

The study aimed (1) to evaluate the prevalence of these types of PKP before 4 months post-ACLR, (2) to measure their consequences on the knee flexors strength, and (3) to evaluate the role of the type of ACLR. From a cohort of patients operated on with hamstring tendon procedures, the persistent and the recurrent PKP were sought at 4 months post-ACLR. The evolution of isokinetic muscle strength recovery in PKP subjects was compared with those of nonpainful subjects. The functional deficit was measured at 6/7 months post-ACLR by a hop test.

RESULTS

Three hundred seventeen subjects (25.8 [6.0] y) were included. At 4 months post-ACLR, 2 populations were identified based on the recurrent onset of PKP (PKP+, n = 40) or the absence of knee pain (PKP-, n = 277). The prevalence of PKP was 8.3%. At the fourth month post-ACLR, the PKP+ group had a higher flexor strength deficit compared with the PKP- group (limb symmetry index at 60°/s: 67.2% [12.4%] vs 84.3% [12.6%]; P < .05). At 6/7 months, the loss of strength persisted (limb symmetry index at 60°/s: 82.3% [13.4%] vs 87.7% [12.8%]; P < .05). The hop test deficit was comparable, and no difference was shown according to the type of graft.

CONCLUSIONS

Persistent and recurrent PKP during the rehabilitation period were not uncommon and were associated with a worsening of flexors strength loss on the ACLR side.

Return to the Pre-Injury Level of Sport after Anterior Cruciate Ligament Reconstruction: A Practical Review with Medical Recommendations

Returning to sport after anterior cruciate ligament reconstruction (ACLR) can be a challenging and complex process for the athlete, with the rate of return to the pre-injury level of sport observed to be less than athlete expectations. Of the athletes that do return to sport (RTS), knee re-injury rates remain high, and multiple studies have observed impaired athletic performance upon RTS after ACLR as well as reduced playing time, productivity, and career lengths. To mitigate re-injury and improve RTS outcomes, multiple RTS after ACLR consensus statements/clinical practice guidelines have recommended objective RTS testing criteria to be met prior to medical clearance for unrestricted sports participation. While the achievement of RTS testing criteria can improve RTS rates after ACLR, current criteria do not appear valid for predicting safe RTS. Therefore, there is a need to review the various factors related to the successful return to the pre-injury level of sport after ACLR, clarify the utility of objective performance testing and RTS criteria, further discuss safe RTS decision-making as well as present strategies to reduce the risk of ACL injury/re-injury upon RTS. This article provides a practical review of the current RTS after ACLR literature, as well as makes medical recommendations for rehabilitation and RTS decision-making after ACLR.

Long-term effects of non-weight bearing and immobilization after anterior cruciate ligament reconstruction on joint contracture formation in rats

PURPOSE

Non-weight bearing improves and immobilization worsens contracture induced by anterior cruciate ligament reconstruction (ACLR), but effect persistence after reloading and remobilization remains unclear, and the combined effects of these factors on ACLR-induced contracture are unknown. We aimed to determine 1) whether the effects of short-term (2-week) non-weight bearing or immobilization after ACLR on contracture would be sustained by reloading or remobilization during a 10-week observation period, and 2) how the combination of both interventions compared to the outcome of either alone.

METHODS

We divided 88 ACL-reconstructed male rats into four groups: non-intervention, non-weight bearing, joint immobilization, and both interventions. Interventions were performed for 2 weeks, followed by rearing without intervention. Twelve untreated rats were used as controls. At 2, 4, and 12 weeks post-surgery, we assessed range of motion (ROM) and histological changes.

RESULTS

ACLR resulted in persistent loss of ROM, accompanied by synovial shortening, capsule thickening, and osteophyte formation. Two weeks of non-weight bearing increased ROM and reduced osteophyte size, but the beneficial effects disappeared within 10 weeks after reloading. Two-week immobilization decreased ROM and facilitated synovial shortening. After remobilization, ROM partially recovered but remained below non-intervention levels at 12 weeks. When both interventions were combined, ROM was similar to immobilization alone.

CONCLUSIONS

The beneficial effects of 2-week non-weight bearing on contracture diminished within 10 weeks after reloading. The adverse effects of 2-week immobilization on contracture persisted after 10 weeks of remobilization. The effects of the combined use of both interventions on contracture were primarily determined by immobilization.

Prolonged Physiotherapy after Anterior Cruciate Ligament Reconstruction Does Not Improve Muscular Strength and Function

Background: After the rupture of the anterior cruciate ligament (ACL), surgery is proposed in the case of knee instability or for athletes who want to return to a pivotal and/or contact sport. The current trend is to extend physiotherapy sessions until a patient's return to sport. We aimed to assess the interest in prolonging the physiotherapy sessions up to 4 postoperative months to restore muscle knee strength and function. Methods: From a historical cohort, 470 patients (24.3 ± 8.7 years) were included; 312 (66%) were males. They all had undergone a primary ACL reconstruction with a hamstring procedure. The number of physiotherapy sessions was established at 4 postoperative months. The main study parameters to assess the benefit of prolonged physiotherapy were the isokinetic limb symmetry index (LSI) for the quadriceps and the hamstrings as well as the Lysholm score. Results: At 4 postoperative months, 148 patients (31.4%) still had physiotherapy sessions. This group had performed 49 ± 14 physiotherapy sessions at the time of evaluation compared to 33 ± 9 sessions performed by the group that stopped physiotherapy at 3 months post-ACL reconstruction. The isokinetic knee LSI and the Lysholm score were not different between the two groups. Continued physiotherapy sessions were associated with female gender, previous high sport level, meniscal repair, lateral tenodesis and outpatient rehabilitation at the beginning of the rehabilitation management, while knee pain complications were not associated. Conclusions: No significant correlation was found between the number of physiotherapy sessions and the knee strength LSI or the Lysholm score. Prolonging patient physiotherapy sessions after 3 months post-ACL reconstruction seems ineffective in improving knee strength recovery and function.

The effects of weight bearing after ACL reconstruction on joint contracture in rats

PURPOSE

Joint contractures after anterior cruciate ligament (ACL) reconstruction are a serious problem. Given the uncertain effects of weight bearing after ACL reconstruction on contractures, this study was conducted to examine such effects.

MATERIALS AND METHODS

To control the amount of weight bearing, ACL-reconstructed rats were reared with either untreated (small weight bearing; weight bearing during locomotion was 54% of pre-surgery at minimum), hindlimb unloading (non-weight bearing), or sustained morphine administration (large weight bearing; weight bearing during locomotion was maintained at 80% or more of pre-surgery) conditions. Untreated rats were used as controls. Knee extension range of motions (ROMs) before (includes myogenic and arthrogenic factors) and after myotomy (includes arthrogenic factor only) and fibrotic reactions in the joint capsule were assessed 7 and 14 days post-surgery.

RESULTS

ACL reconstruction significantly reduced ROMs both before and after myotomy and induced fibrosis in the joint capsule accompanying upregulation of fibrosis-related genes (i.e., type I and III collagens and transforming growth factor-β1) at both time points. Morphine administration increased the ROM before myotomy, but not after myotomy 7 days post-surgery. Unloading after ACL reconstruction improved ROMs both before and after myotomy at both time points. In addition, unloading after ACL reconstruction attenuated fibrotic reactions in the joint capsule.

CONCLUSIONS

Our results suggest that morphine administration improves myogenic contractures in parallel with an increase in the amount of weight bearing. Unloading after ACL reconstruction is effective in reducing both myogenic and arthrogenic contractures.

Arthrofibrosis risk factors after anterior cruciate ligament reconstruction

Introduction

Knee arthrofibrosis is a disabling complication after anterior cruciate ligament reconstruction (ACLr). Different risk factors have been studied but are still controversial because of a diagnosis made only during reoperations for the treatment of the stiffness, which underestimates the occurrence rate. We aimed to confirm risk factors of arthrofibrosis after ACLr in case of clinically made diagnoses.

Methods

Ninety-two athletes with clinically diagnosed arthrofibrosis, complicating a primary ACLr, were compared to 482 athletes with ACLr without any complications. Usually considered risk factors were studied: age under 18, female, Body Mass Index (BMI ≥ 25), high sport level, time from ACL injury to ACLr < 1 month, Bone-Patella-Tendon-Bone surgical procedure (BPTB), meniscal repair, and intensive rehabilitation. Binary logistic regression was carried out to confirm or refute these risk factors.

Results

Female, time from ACL injury to ACLr < 1 month, BPTB procedure, meniscal repair, and BMI ≥ 25 were not confirmed as risk factors. Previous competitive sport level assessed by Tegner score was the only risk factor identified, OR: 3.56 (95%IC: 2.20-5.75; p = 0.0001). Age < 18, OR: 0.40 (95%IC: 0.19-0.84; p = 0.015) and inpatient rehabilitation program, OR: 0.28 (95%IC: 0.17-0.47; p = 0.0001), were protective factors.

Discussion

Competitive athletes are at risk of arthrofibrosis after ACLr and should benefit from protective inpatient rehabilitation program.

The effects of immobilization duration on joint contracture formation after anterior cruciate ligament reconstruction in rats

BACKGROUND

Both myogenic and arthrogenic factors contribute to contracture formation after anterior cruciate ligament reconstruction surgery. However, effects of immobilization duration on myogenic and arthrogenic contractures after surgery are unknown. We examined the effects of immobilization duration on contracture formation.

METHODS

Rats were divided into groups according to treatment received: untreated control, knee immobilization, anterior cruciate ligament reconstruction, and anterior cruciate ligament reconstruction plus immobilization. Extension range of motion before and after myotomy as well as histomorphological knee changes were assessed two or four weeks after experiment commencement. Range of motion before myotomy mainly represents contractures due to myogenic factors. Range of motion after myotomy represents arthrogenic factors.

FINDINGS

Range of motion before and after myotomy was decreased in the immobilization, reconstruction, and reconstruction plus immobilization groups at both timepoints. In the reconstruction plus immobilization group, range of motion before and after myotomy was significantly smaller than in the immobilization and reconstruction groups. Shortening and thickening of the posterior joint capsule was induced in the immobilization and reconstruction groups. In the reconstruction plus immobilization group, capsule shortening was facilitated via adhesion formation, as compared to the immobilization and reconstruction groups.

INTERPRETATION

Our results indicate that immobilization after anterior cruciate ligament reconstruction surgery facilitates contracture formation via exacerbation of both myogenic and arthrogenic contractures within two weeks. Capsule shortening would be one of the main mechanisms for severe arthrogenic contracture observed in the reconstruction plus immobilization group. Periods of joint immobilization after surgery should be minimized to reduce contracture.

Consequences of anterior knee pain after anterior cruciate ligament reconstruction: A 2015-2020 cohort study

Anterior cruciate ligament reconstruction (ACLR) using hamstring tendon (HT) graft aims to stabilise the knee, but it may bring some complications like anterior knee (AKP) pain that can have consequences on the functional aspect of this surgery. The aim of this study was to compare isokinetic knee strength and functional outcomes between patients with and without AKP following an ACLR using HT graft during the first-year post-surgery. Three hundred and thirty subjects operated by ACLR using hamstring tendon graft were included in our retrospective cohort and divided into two groups: a group with AKP (AKP+ group) and one without AKP (AKP-group). In our population, 14.8% of the patients had AKP. At 4 post-operative months, subjects with pain had lower isokinetic strength limb symmetry index (LSI) for knee flexors and extensors, and a lower Lysholm score than subjects without pain (p < 0.0001). These differences did not persist at 7 post-operative months, and there was no difference in the one-leg hop test. After multivariate analysis, we highlighted the impact of time on the evolution of these parameters. Yet, the exact definition of AKP after ACLR remains to be clearly defined since an imprecise diagnosis may lead to inappropriate management. Pre-operative information about this type of complication, which evolves favourably with time, could be useful for patients. Indeed, AKP can occur after ACLR, even if a HT graft has been used, compared to other surgical procedures using the knee extensor apparatus as patellar tendon graft (AKP is associated with the donor site morbidity). In case of AKP after ACLR, monitoring the muscle inhibition by isokinetic tests may enable clinicians to adapt the retraining and the return to sport.

Patellar tendon lengthening and augmentation with quadriceps tendon graft for treatment of severe patella infera

BACKGROUND

Patella infera represents a permanent abnormally low position of the patella with three characteristics: distal position of the patella in the femoral trochlea, permanent shortening of the patellar tendon, and decreased distance between the inferior pole of the patella and the articular surface of the tibia. Several surgical techniques have been described to resolve this disabling condition with varying outcomes.

HYPOTHESIS

Lengthening of the shortened patellar tendon with augmentation using a quadriceps tendon graft in combination with excessive intra-articular release improve knee function in patients presenting with severe and permanent patella infera.

METHODS

Nine patients (four males, five females) with significant patella infera were treated between 2004 and 2020. The low position of the patella was documented using the Caton-Deschamps index. The Tegner Lysholm knee scoring scale and the Numerical Rating Scale (NRS) for pain were used as outcome measures before surgery and at follow up. Complete data were available in 100% of cases at 12 months follow up, and in 78% at final follow up.

RESULTS

The average follow up was 4.2 years (range, 1-16 years). The Tegner Lysholm score improved from a mean preoperative score of 43.8 to a mean postoperative score of 80.5. The median NRS status decreased from an average of 6.7 (range, 5-8) to 2.3 (range, 1-7). The median preoperative flexion was 103.3° (range, 40-125°), rising to 126.6° (range, 40-145°). The median preoperative Caton-Deschamps ratio of 0.32 (range, 0-0.6) improved to 0.99 (range, 0.9-1.1) at final follow up. Two patients needed additional surgical treatment (arthroscopic scar tissue removal and proximalisation of the tibial tuberosity).

CONCLUSION

Lengthening of a shortened patellar tendon with augmentation using a quadriceps tendon graft combined with excessive intra-articular release is an individually adapted surgical salvage procedure to treat permanent patella infera. It improves knee function and yields good to excellent results in most cases.

Knee Strength Assessment and Clinical Evaluation Could Predict Return to Running after Anterior Cruciate Ligament Reconstruction Using Patellar Tendon Procedure

BACKGROUND AND OBJECTIVES

Muscle knee strength is a major parameter that allows return to running. Isokinetic strength parameters may predict return to running 4 months after ACLR using the bone-patellar-tendon-bone procedure.

MATERIALS AND METHODS

The isokinetic knee strength of 216 patients (24.5 ± 5 years) was measured 4 months after surgery, and progressive return to running was allowed. The effectiveness of return to running was reported at 6 months. Return to running prediction was established using multivariate logistic regression. Predictive parameters were presented with a ROC curve area to define the best cut-off, with sensibility (Se) and specificity (Sp).

RESULTS

A model was established, including the limb symmetry index (LSI), and 103 patients (47.6%) were able to run between the fourth and the sixth month after surgery. These patients presented significantly fewer knee complications, a better Lysholm score, a better Quadriceps and Hamstring LSI and better quadriceps strength reported for body weight on the operated limb. The best model was established including the Quadriceps and Hamstring LSI at 60°/s and the Lysholm score. The cut-off for Quadriceps LSI was 60% (ROC curve area: 0.847; Se: 77.5%; Sp: 77%), for Hamstring LSI 90% (ROC curve area: 0.716; Se: 65.7%; Sp: 60.2%) and for Lyshom score 97 points (ROC curve area: 0.691; Se: 65%; Sp: 66%).

CONCLUSION

Four months after ACLR using a bone-patellar-tendon-bone procedure, the Quadriceps and Hamstring LSI associated to the Lysholm score could help make the decision to allow return to running.

Relevant Strength Parameters to Allow Return to Running after Primary Anterior Cruciate Ligament Reconstruction with Hamstring Tendon Autograft

After anterior cruciate ligament reconstruction (ACLR), a progressive process is followed from rehabilitation to the return to sport including a crucial step known as the return to running. Return to running (RTR) can be predicted by an isokinetic knee strength assessment at 4 months post-surgery. All patients who had primarily undergone ACLR with a hamstring autograft procedure between 2010 and 2020 were included in this study. Four months after surgery, patients were evaluated using an isokinetic knee strength test. Patients were monitored until the 6th month post-surgery to see if they had returned to running. Comparisons were carried out between the two groups—the RTR and the no-RTR. A multivariate logistic regression analysis was used to predict the RTR status from explicative parameters. Receiver Operating Characteristic (ROC) curves were established to identify cutoffs with their characteristics. A total of 413 patients were included and 63.2% returned to running at 4 months post-surgery. The mean Lysholm score, knee complication rate, and isokinetic parameters were statistically different between both groups. Using a multivariate logistic regression model and ROC curves, the best isokinetic parameter to assist with the decision to allow an RTR was the quadriceps limb symmetry index at 60°/s with a cutoff of 65%. The hamstring LSI at 180°/s could be added (cutoff of 80%) to slightly increase the prediction of an RTR. Quadriceps strength normalized to body weight at 60°/s is a useful parameter (cutoff: 1.60 Nm/kg) but measurements on both sides are necessary. Isokinetic parameters are objective parameters to allow a return to running at 4 months after ACLR with a hamstring procedure.

Therapeutic Patient Education after Anterior Cruciate Ligament Reconstruction: Evaluation of the Knowledge and Certitudes with a Self-Report Questionnaire

Therapeutic education aims to help patients acquire skills and knowledge, and to improve psychosocial aspects to manage chronic disease. After anterior cruciate ligament reconstruction (ACLR), only 35 to 60% of the patients are able to go back to their previous sport. Return to sport depends on the motivation of the patient. No therapeutic education has already been proposed. We aimed to evaluate the effect of therapeutic education sessions on knowledge improvement during inpatient rehabilitation after ACLR, compared to patients operated with the same surgical technic, but who had no therapeutic education because of outpatient rehabilitation. Sessions were performed by a multidisciplinary team. The evaluation of the knowledge was performed with a true or false 12-items self-report questionnaire. Fifty-four patients were studied and compared to 54 patients with no therapeutic education. The educated and the non-educated groups were comparable. The number of correct answers increased from 73% before therapeutic education to 95% at the end of the hospitalization (p < 0.001). This improvement persisted over time with 91.5% of correct answers at four months (p = 0.94). The non-educated group had 70% of correct answers. This was significantly lower than the results obtained from the educated group at four months (p < 0.001). It was comparable to the result obtained before therapeutic education (p = 0.91). Therapeutic patient education performed during hospitalization for rehabilitation enables patients to have a better knowledge of the stages from rehabilitation to return to sport and the risks of complication after ACLR.

Consequences of Patellar Tendinopathy on Isokinetic Knee Strength and Jumps in Professional Volleyball Players

Patellar tendinopathy (PT) in professional volleyball players can have an impact on their careers. We evaluated the impact of this pathology in this specific population in terms of isokinetic strength and jumping performances. Thirty-six professional male volleyball players (mean age: 24.8 ± 5.2) performed isokinetic knee assessments, single-leg countermovement jumps and one leg hop test. They filled out the Victorian Institute of Sport Assessment-Patella (VISA-P) score. Two groups were assessed: “PT group” (n = 15) and “control group” (n = 21). The VISA-P score was lower in the PT group (p < 0.0001). No difference was found between the isokinetic strength limb symmetry index and the jump performance limb symmetry index. The healthy legs of the control group were compared with the affected (PT+) and the unaffected legs (PT−) of the PT group. Compared with the healthy legs, both PT+ and PT− legs showed decreased values of quadriceps and hamstring strengths. Only PT+ legs scored lower than healthy legs in countermovement jumps and hop tests. No differences were found between PT+ and PT− legs for muscle strengths and jumps. A low correlation existed between quadriceps strength and jumping performances (r > 0.3; p < 0.001). Volleyball players with PT showed a decrease in the isokinetic knee strength. This strength deficit was found both on the symptomatic legs and the asymptomatic ones. Jumps were only significantly altered on the pathological legs. Highlighting that the unaffected limbs were also impaired in addition to the affected limbs may help provide a better adaptation of the rehabilitation management.

Arthrogenic Muscle Inhibition Following Knee Injury or Surgery: Pathophysiology, Classification, and Treatment

Background

Arthrogenic muscle inhibition (AMI), a process in which quadriceps activation failure is caused by neural inhibition, is common following knee injury or surgery. No classifications exist to describe the variable presentations of AMI following knee injury.

Indications

AMI can result in significant morbidity following knee injury, and it is essential to recognize and treat. It is crucial to identify patients at higher risk of postoperative complications as surgery should be delayed for specific rehabilitation programs. Understanding the pathophysiology of AMI is vital as this can guide therapeutic interventions.

Technique Description

AMI following knee injury can present in a variety of ways including inhibition of the vastus medialis obliquus (VMO) muscle, extension deficits due to hamstring contracture, as well as chronic extension deficits. They also respond differently to conventional treatment modalities and often require longer and specific rehabilitation programs. Therefore, we propose a classification to define these different presentations.

Results

Grade 0 is a normal VMO contraction. Grade 1a is when VMO contraction is inhibited but activation failure is reversible with simple exercises while Grade 1b requires longer and specific rehabilitation programs. Grade 2a is when VMO contraction is inhibited with an associated extension deficit due to hamstring contracture, but activation failure and loss of range of motion is reversible with simple exercises. However, Grade 2b is refractory to simple exercises, and longer and specific rehabilitation programs are required. Grade 3 is a chronic extension deficit that is irreducible without extensive posterior arthrolysis.

Conclusion

In conclusion, AMI is a process in which quadriceps activation failure is caused by neural inhibition and is common following knee injury or surgery. Not taking AMI into account preoperatively can result in a very high risk of stiffness postoperatively. We propose a classification for AMI following knee injury or surgery, which describes different presentations and can be used to guide management.