Validity of the Uninjured Limb as a Control for Preoperative Assessment in Anterior Cruciate Ligament Reconstruction.

Monitoring muscle atrophy in patients undergoing anterolateral cruciate ligament reconstruction is pivotal for optimizing postoperative recovery. Conventionally, the uninjured contralateral limb serves as the control. However, its relevance in patients with prolonged physical activity hiatus due to knee instability remains uncertain. Our objectives were to compare limbs within a control group by assessing combined force measurements, cross-sectional areas (CSAs), and neuromuscular activation. In addition, we compared the contralateral limb of the surgery group preoperatively to the control group. This prospective controlled study (evidence level 2) included 40 healthy subjects (HG) and 30 patients scheduled for ACL surgery (SG). Both groups underwent identical assessments. The two HG limbs were compared to establish the standard difference for all assessed variables, whereas SG contralateral limb was compared with the mean of the control limbs. For HG, the comparisons between limbs showed no significant differences in muscle strength, CSA area, or electromyographic parameters. Similarly, comparisons between the SG contralateral limb and the mean of HG limbs revealed no significant differences in isometric and dynamic strength for the quadriceps and hamstrings (2.5 ± 0.5 and 2.6 ± 0.9 N.m/kg, and 1.7 ± 0.3 and 1.7 ± 0.4 N.m/kg, respectively). Neuromuscular activation and fatigue patterns were also comparable between groups. CSAs discrepancies were attributed to differences in body mass index between groups. These findings indicate that the contralateral limb in ACL_injured patients is functionally similar to that of healthy controls, supporting its use as a valid reference for monitoring postoperative recovery. Trial Registration: NCT03200678.