Using the Single-Leg Hop Test to Determine Knee Extension Strength After Anterior Cruciate Ligament Reconstruction

Area of Science:

• Orthopedics
• Sports Medicine
• Rehabilitation Science

Background:

• Assessing athlete readiness for return to sports after anterior cruciate ligament reconstruction (ACLR) often involves strength tests and the single-leg hop test.
• Confounding variables can impact the relationship between the single-leg hop test and actual strength, potentially limiting its clinical usefulness.

Purpose of the Study:

• To investigate if confounding variables affect the relationship between single-leg hop performance and knee extension/flexion torque.
• To determine if single-leg hop distance can predict the strength of the ACL-reconstructed limb.

Main Methods:

• A cross-sectional study (Level of evidence, 3) included 35 male athletes post-ACLR with hamstring tendon autografts.
• Researchers assessed single-leg hop distance and knee extension/flexion strength, analyzing relationships using correlation coefficients, linear modeling, and logistic regression.

Main Results:

• Strength variables showed a moderate correlation with knee extension strength and single-leg hop distance, but with wide confidence intervals.
• Predicting knee extension strength based on single-leg hop distance, flexion strength, and age had a mean error of 18%.
• Logistic regression incorrectly classified 23% of participants regarding knee extension strength symmetry (LSI <85%).

Conclusions:

• The relationship between the single-leg hop test and knee extension strength after ACLR is only moderately strong and imprecise.
• Predicting knee extension strength using the single-leg hop test introduces clinically significant error.
• The single-leg hop test likely lacks clinical utility for accurately assessing knee extension strength in this population.