Factors affecting knee abduction during weight-bearing activities in individuals with anterior cruciate ligament reconstruction

Objective: To investigate if muscle strength and muscle activation patterns are associated with increased knee abduction during two functional tasks, commonly used in rehabilitation for individuals with anterior cruciate ligament reconstruction (ACLR).

Design: Cross-sectional study.

Setting: Laboratory.

Participants: 24 women and 29 men approximately 7 months after ACLR.

Main Outcome Measures: Isometric peak torque of the trunk and lower extremity muscles were determined during maximal voluntary contractions. Trunk and lower extremity average muscle activation amplitude and peak knee abduction were evaluated during the single-leg squat (SLS) and the single-leg hop for distance (SLHD) for the injured side. Separate backward regressions were performed for men and women.

Results: In women, lower knee flexion and extension strength were associated with greater peak knee abduction during the SLS (B= 4.63 – 18.26, p≤0.036); lower knee flexion strength and iliocostalis activation on the non-injured side were associated with greater peak knee abduction during the SLHD (B= 0.60 – 20.48, p≤0.043). No associations between muscle function and peak knee abduction were found in men.

Conclusions: Muscle function may contribute differently to knee abduction in men and women after ACLR. This should be considered when designing rehabilitation programs to reduce knee abduction in these patients.