Knee Extensor and Flexor Strength are Related to One-Leg Hop Distances in Three Directions in Patients Six Months After Anterior Cruciate Ligament Reconstruction

Abstract

Background: When planning rehabilitation and conditioning for performance enhancement and a return to sports after anterior cruciate ligament reconstruction, identifying the elements of physical function associated with one-leg hop is important. The purpose of this study was to clarify the relationship between one-leg hop distances in 3 directions and knee extensor and flexor strengths at 6 months after reconstruction.Methods: Participants were 47 patients taking part in training sessions for sports involving cutting, pivoting, and jump-landing 6 months after reconstruction using a hamstring tendon. Demographics, activity scale score, days before and after reconstruction, and meniscus surgery procedure were analyzed. One-leg hop distances in 3 directions (anterior, lateral, and medial) and isokinetic strengths of knee extension and flexion were measured. Simple regression analyses using Spearman's rank correlation coefficient were performed to assess relationships between one-leg hop distances and knee strengths.Results: In the involved limb, correlations between one-leg hop distance in 3 directions and knee strengths were significant and effect sizes ranged from medium to large. Correlation coefficients between all one-leg hop parameters and knee extension/flexion strengths at an angular velocity of 180°/s were greater than those of 60°/s.Conclusions: Knee strength showed moderate to high associations with lateral and medial one-leg hop distances in addition to anterior one-leg hop distance. The results of this study will be useful in planning and teaching conditioning to improve multi-directional one-legged hop skills and improve knee strength for a full-scale return to sports after reconstruction.