Greater muscle co-contraction results in increased tibiofemoral compressive forces in females who have undergone anterior cruciate ligament reconstruction.

Individuals who have undergone ACL reconstruction (ACLR) have been shown to have a higher risk of developing knee osteoarthritis (OA). The elevated risk of knee OA may be associated with increased tibiofemoral compressive forces. The primary purpose of this study was to examine whether females with ACLR demonstrate greater tibiofemoral compressive forces, as well as greater muscle co-contraction and decreased knee flexion during a single-leg drop-land task when compared to healthy females. Ten females with ACLR and 10 healthy females (control group) participated. Each participant underwent two data collection sessions: (1) MRI assessment and (2) biomechanical analysis (EMG, kinematics, and kinetics) during a single-leg drop-land task. Joint kinematics, EMG, and MRI-measured muscle volumes and patella tendon orientation were used as input variables into a MRI-based EMG-driven knee model to quantify the peak tibiofemoral compressive forces during landing. Peak tibiofemoral compressive forces were significantly higher in the ACLR group when compared to the control group (97.3 ± 8.0 vs. 88.8 ± 9.8 N · kg(-1)). The ACLR group also demonstrated significantly greater muscle co-contraction as well as less knee flexion than the control group. Our findings support the premise that individuals with ACLR demonstrate increased tibiofemoral compression as well as greater muscle co-contraction and decreased knee flexion during a drop-land task. Future studies are needed to examine whether correcting abnormal neuromuscular strategies and reducing tibiofemoral compressive forces following ACLR can slow the progression of joint degeneration in this population.