Background Asymmetries in knee motion have been identified as a risk factor for second anterior cruciate ligament (ACL)injury.
Objective To investigate the kinematics and kinetics of knee joint and ground reaction force during landing after ACL reconstruction (ACLR).
Design Controlled laboratory study.
Setting The patients after ACLR and being cleared to return to competitive sports.
Patients Four males and 8 females (23.2 years) at 43 (8–152) months postoperatively.
Assessment of Risk Factors The subjects performed a drop vertical jump by dropping directly down off a box, and immediately performing a maximum vertical jump. The kinematic and kinetic data of the knee joint during landing were measured using 3-dimensional motion analysis system. The concentric peak torque of the quadriceps and hamstring muscle were measured using a dynamometer. KOOS were used to measure patient-reported outcomes.
Main Outcome Measurements The knee flexion and varus/valgus angle, maximum knee valgus moment and peek vertical ground reaction force (VGRF) during landing were measured.
Results The knee kinematics was not significantly difference between reconstructed and intact knees. Maximum knee valgus moment of reconstructed knees during landing was 0.2±0.1 Nm/kg/m, and that of intact knees was 0.4±0.2 Nm/k/m. Peek VGRF of reconstructed knees was 1.2±0.2 N/BW, and that of intact knees was 1.7±0.3 N/BW. There was significant difference in maximum knee valgus moment and peak VGRF between reconstructed and intact knees (p<0.05). Normalized muscle strength was above 80%. There were no significant correlations between knee valgus moment, VGRF, muscle strength and KOOS.
Conclusions Significant asymmetry of knee valgus moment and VGRF has still been observed in ACL reconstructed patients who were satisfied to return to sports, and these were difficult to be predicted by muscle strength and subjective knee function. Assessments of biomechanical asymmetry may support a safer return to sports minimizing re-injury and contralateral injury rate for athletes.