iFEMG-Based Muscle Function Assessment for Rehabilitation Monitoring After Knee Anterior Cruciate Ligament Repair Surgery.

The ligaments and muscles of the knee joint play an important role in maintaining knee joint stability, ensuring smooth movement of the lower limbs. However, the assessment and monitoring of the muscle function following anterior cruciate ligament (ACL) reconstruction are hindered due to the inherent constraints of conventional clinical evaluation techniques. This study employed an integrated flexible force-electromyography (iFEMG) system to quantify differences in neuromuscular activities and associated mechanical properties between affected and healthy sides during post-ACL reconstruction rehabilitation. 12 patients performed supine and prone straight leg raises under three load conditions. Bilateral iFEMG signals were recorded from six lower limb muscles. Linear mixed-effects modeling was applied to quantify bilateral differences in muscle activation patterns based on signal-derived features. Across multiple thigh muscles, the affected limb exhibited elevated agonist activation and sustained antagonist co-activation relative to the healthy side, with side-specific differences in load-response slopes. By characterising how each limb scales with load and how the affected limb deviates from the healthy reference across the loading range, the proposed approach reframes rehabilitation assessment from single-load snapshot comparisons to load-graded dynamic profiling, offering a quantitative framework for mechanism-informed evaluation in post-ACLR rehabilitation.