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.

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

OBJECTIVE: To determine whether reported therapeutic interventions for arthrogenic muscle inhibition (AMI) in patients with ACL injuries, following ACL reconstruction, or in laboratory studies of AMI, are effective in improving quadriceps activation failure when compared with standard therapy in control groups. DESIGN: A scoping review of the efficacy of interventions was conducted in accordance with the methodological framework of Arksey and O'Malley and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Search terms included 'arthrogenic muscle inhibition', 'quadriceps activation following knee injuries', 'anterior cruciate' or 'knee' combined with 'quadriceps activation', 'quadriceps inhibition', 'corticomotor', 'arthrogenic', 'brain activation' and 'neuroplasticity'. Articles were evaluated for risk of bias using the PEDro (Physiotherapy Evidence Database) criteria. The overall quality of evidence for each intervention was assessed using Grading of Recommendations Assessment, Development and Evaluation (GRADE). DATA SOURCES: PubMed, EMBASE and Cumulative Index to Nursing and Allied Health Literature databases. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Isolated case reports and articles reporting outcomes in patients with chronic disease or major trauma were excluded. All other original research articles were included. RESULTS: 780 potential articles were identified. 20 met the inclusion criteria. These studies provided a moderate quality of evidence to support the efficacy of cryotherapy and physical exercises in the management of AMI. There was low-quality evidence for efficacy of neuromuscular electrical stimulation and transcutaneous electrical nerve stimulation, and very low-quality evidence for efficacy of ultrasound and vibration. CONCLUSIONS: This scoping review demonstrated moderate-quality evidence for the efficacy of cryotherapy and physical exercises in improving quadriceps activation failure after ACL injury and reconstruction. These therapeutic modalities are therefore recommended in the management of AMI.