Objective: To evaluate the change in hamstring (H):quadriceps (Q) ratio following anterior cruciate ligament (ACL) rupture during isokinetic knee extension and flexion at 30 degrees of flexion which is important for knee dynamic function.
Methods: A study was performed in 25 male complete unilateral ACL ruptures. Isokinetic concentric and eccentric quadriceps and hamstring muscle tests in both the deficient knees and intact knees were performed at 60°/s, respectively. At 30 degrees of flexion, the average torque of quadriceps and hamstring, Qe:Qc ratios (ratios of eccentric quadriceps to concentric quadriceps muscle torque), He:Hc ratios (eccentric hamstring to concentric hamstring), Hc:Qc ratios (concentric hamstring to concentric quadriceps), He:Qc ratios (eccentric hamstring to concentric quadriceps), and Hc:Qe ratios (concentric hamstring to eccentric quadriceps) were calculated. Wilcoxon matched-pairs signed-ranks test was used.
Results: At 30 degrees of knee flexion, a significant reduction (P<0.05) in the average torque of quadriceps was observed at concentric and eccentric 60°/s produced by the deficient-side compared with the intact side. In addition, Hc:Qc, He:Qc, and Qe:Qc significantly increased on the ACL-deficient side.
Conclusion: The change in H :Q ratio in the mode of isokinetic 60°/s at 30 degrees of knee flexion might therefore be a new tool to objectively document muscle function in ACL-deficient knee.