Limb differences in hamstring muscle function and morphology after anterior cruciate ligament reconstruction.

Objective: To compare inter-limb differences in hamstring strength, muscle volume, and neural activity between individuals with anterior cruciate ligament reconstruction (ACLR) and healthy controls, and to identify associations between hamstring neuromuscular function and subjective knee function.

Design: Cross-sectional.

Setting: Laboratory.

Participants: Eleven participants with a history of ACLR (69.45 ± 22.48 months from surgery) and eleven healthy matched controls.

Main Outcome Measure(s): Hamstring isokinetic torque at 60 and 240°•s, muscle volume, and medial and lateral hamstring electromyographic (EMG) activity during a single leg hop task were all evaluated during one study visit. Percent limb-differences (%LD) were calculated between each outcome measure; greater inter-limb differences indicated greater asymmetries between limbs. The International Knee Documentation Committee (IKDC) scores were used to determine associations between subjective knee function and each outcome measure.

Results: Individuals with ACLR had large magnitude inter-limb differences in medial hamstring EMG (p = .04; d = 0.94), biceps femoris short head volume (p = .02; d = 1.07) and semitendinosus (p = .03; d = 1.07) volume. Lower semimembranosus volume was associated with lower IKDC scores (r = 0.754; p = .012).

Conclusions: We observed greater inter-limb differences in medial hamstring EMG, and semitendinosus and long head of the biceps femoris volume, which may negatively influence knee function years after ACLR.