Arthrogenic Muscle Inhibition

Arthrogenic muscle inhibition (AMI) is a common neurological impairment following knee surgery that limits voluntary quadriceps activation and delays functional recovery. Persistent AMI may contribute to muscle weakness, altered gait, and poorer rehabilitation outcomes. Although several rehabilitation strategies have been proposed, no complementary intervention has consistently demonstrated strong evidence for improving AMI. This prospective single-case experimental study aims to evaluate whether visual biofeedback based on surface electromyography (sEMG) improves quadriceps motor performance during standard rehabilitation. Each participant will complete eight standardized rehabilitation sessions, including four sessions with visual sEMG biofeedback and four sessions without visual feedback. The order of the two conditions will be randomized, allowing each participant to serve as his or her own control. The primary objective is to determine whether visual sEMG biofeedback improves the accuracy of quadriceps contraction, assessed by the percentage deviation from a predefined target. Secondary objectives include evaluation of motor engagement, motor control, muscle activation, perceived exertion, and pain. Between three and five adult patients presenting AMI after knee surgery will be included. Because recovery patterns are highly individualized, a Single-Case Experimental Design (SCED) with repeated within-subject measurements has been selected to characterize individual treatment responses while minimizing inter-individual variability

The goal of this observational study is to explore the significance of subject-reported outcomes and clinical parameters in relation to the occurence of prolonged presence of arthrogenic muscle responses (AMR) in anterior cruciate ligament (ACL) reconstructed patients. The main questions it aims to answer are: 1\. Is there a link between the long-term occurence of AMR in ACL reconstructed patients and the level of kinesiophobia experienced before or after their ACL surgery? We hypothesize that ACL patients with higher levels of kinesiophobia are more likely to exhibit prolonged AMR as an unconscious reaction to protect their affected knee joint. 2\. Is the long-term presence of AMR in ACL reconstructed patients linked to their subjective knee function and stability (at certain time points throughout their recovery)? Our hypothesis is that poorer subjective knee function and stability might be associated with the presence of prolonged arthrogenic muscle responses in ACL reconstructed patients. 3\. Is the prolonged presence of AMR in ACL reconstructed patients linked to their pain levels (at certain time points throughout their recovery)? Our hypothesis is that ACL patients with higher pre- and/or postsurgical pain levels may exhibit a higher degree of long-lasting AMR. 4\. Is the long-term presence of AMR in ACL reconstructed patients linked to clinical parameters such as swelling, isometric quadriceps and hamstrings strength and knee range of motion (at certain time points throughout their recovery)? Our hypothesis is that ACL patients with poorer outcomes in terms of these clinical parameters may be more likely to exhibit prolonged AMR. Participants will: * Fill in the following questionnaires 1 week before surgery and at 1 and 3 months after surgery: * Demopgraphical information * Knee Injury and Osteoarthritis Outcome Score (KOOS) * Lysholm Score (only question 1) * Tegner Activity Scale (current activity level, pre-injury activity level and desired activity level after recovery) * Numeric Rating Score (NRS) for pain levels during the day \& during the night * ACL-Return to Sport after Injury Scale (ACL-RSI) * Complete a testing protocol 5 months after their surgery, which includes bilateral electromyographical measurements of the hamstrings and quadriceps during jumping tasks and a quadriceps inhibition measurement using the interpolated twitch method to evaluate the presence of prolonged AMR.