Lower knee self‐efficacy is associated with greater asymmetries in quadriceps neuromuscular function and jump‐landing biomechanics post‐ACL reconstruction

Purpose To (1) compare psychological factors and asymmetries in quadriceps neuromuscular function and jump‐landing biomechanics between patients with anterior cruciate ligament reconstruction (ACLR) and healthy controls and (2) determine whether psychological factors relate to these asymmetric outcomes in the ACLR cohort. Methods Forty participants (26 patients with ACLR [time since surgery: 39.7 ± 35.1 months] and 14 healthy controls) were included. Psychological assessments included measures of fear of reinjury (Tampa Scale of Kinesiophobia), knee self‐efficacy (Knee Self‐Efficacy Scale) and readiness for return to sport (anterior cruciate ligament‐return to sport after injury). Bilateral quadriceps strength (maximal voluntary isometric contraction) and activation (central activation ratio) were evaluated via a multimodal dynamometer. Bilateral peak knee extension moment (KEM) and peak vertical ground reaction force (vGRF) during jump‐landing were assessed using a three‐dimensional motion capture system. Limb symmetry indices were calculated for all neuromuscular and biomechanical variables. Results Compared to healthy controls, patients with ACLR demonstrated significantly worse psychological outcomes ( p < 0.001 for all questionnaires; Cohen's d = 1.35–1.94) and greater asymmetries in quadriceps strength ( p = 0.016; Cohen's d = 0.84), peak KEM ( p < 0.001; Cohen's d = 1.47) and peak vGRF ( p = 0.002; Cohen's d = 1.10). Among patients with ACLR, lower knee self‐efficacy was moderately to strongly associated with greater asymmetries across all neuromuscular and biomechanical measures ( ρ = 0.420–0.737; p ≤ 0.033). Greater fear of reinjury ( r = −0.403; p = 0.041) and lower readiness for return to sport ( r = 0.522; p = 0.006) were moderately associated with greater asymmetry in peak vGRF. Conclusion Patients with ACLR displayed worse psychological outcomes and greater asymmetries in quadriceps neuromuscular function and jump‐landing biomechanics compared to healthy controls. Knee self‐efficacy was consistently associated with asymmetries in quadriceps neuromuscular function and jump‐landing biomechanics following ACLR. Asymmetry in vGRF may be particularly sensitive to psychological factors in patients with ACLR. Level of Evidence Level III.