The relationship between quadriceps strength asymmetry and knee biomechanics asymmetry during walking in individuals with anterior cruciate ligament reconstruction

Background: Lower extremity movement asymmetries may lead to re-injury and knee osteoarthritis after anterior cruciate ligament (ACL) reconstruction surgery. However, there is no consensus regarding the effect of quadriceps strength asymmetry on lower extremity movement asymmetry after ACL reconstruction. Research question: What is the relationship between quadriceps strength asymmetry and asymmetries in lower extremity kinematics and kinetics during walking in individuals who underwent ACL reconstruction surgery?. Methods: Isometric quadriceps strength, kinematic, and kinetic data during walking were collected from 24 men with unilateral ACL reconstruction. Knee joint angles and moments were reduced. Pearson correlation coefficients between asymmetry in selected knee biomechanics and isometric quadriceps strength asymmetry were determined. Results: The isometric quadriceps strength of the injured leg was significantly lower than that of the uninjured leg (P < 0.001). Knee flexion angles and knee extension moments were smaller in the injured leg than that in the uninjured leg during both loading response (P = 0.007, P = 0.047) and mid-stance phases (P = 0.005, P = 0.028). Isometric quadriceps strength asymmetry was significantly correlated with asymmetry in the peak knee flexion angle during loading response and mid-stance phases (r = -0.48, P = 0.017, r = -0.48, P = 0.017). Isometric quadriceps strength asymmetry was also significantly correlated with asymmetry in the peak knee extension moment during the mid-stance phase (r = -0.44, P = 0.033). Significance: Individuals with ACL reconstruction demonstrate knee movement asymmetry in the sagittal plane. Isometric quadriceps strength asymmetry is significantly correlated with asymmetry in knee flexion angles during the early stance phase and knee extension moments during the mid-stance phase. Rehabilitation programs should emphasise eccentric exercise to beneficially modify quadriceps neuromuscular control.