Activity-Dependent Compensation at the Hip and Ankle at 8 Years After the Reconstruction of Isolated and Combined Posterior Cruciate Ligament Injuries.

BACKGROUND

After posterior cruciate ligament reconstruction (PCLR), functional deficits at the knee can persist. It remains unclear if neighboring joints compensate for the knee during demanding activities of daily living.

PURPOSE

To assess long-term alterations in lower limb mechanics in patients after PCLR.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 28 patients who had undergone single-bundle unilateral isolated or combined PCLR performed stair navigation, squat, sit-to-stand, and stand-to-sit tasks at 8.2 ± 2.2 years after surgery. Motion capture and force plates were used to collect kinematic and kinetic data. Then, 3-dimensional hip, knee, and ankle kinematic data of the reconstructed limb were compared with those of the contralateral limb using statistical parametric mapping.

RESULTS

Side-to-side differences at the knee were primarily found during upward-driven movements at 8 years after surgery. The reconstructed knee exhibited lower internal rotation during the initial loading phase of stair ascent versus the contralateral knee ( = .005). During the sit-to-stand task, higher flexion angles during the midcycle ( = .017) and lower external rotation angles ( = .049) were found in the reconstructed knee; sagittal knee ( = .001) and hip ( = .016) moments were lower in the reconstructed limb than the contralateral limb. In downward-driven movements, side-to-side differences were minimal at the knee but prominent at the ankle and hip: during stair descent, the reconstructed ankle exhibited lower dorsiflexion and lower external rotation during the midcycle versus the contralateral ankle ( = .006 and = .040, respectively). Frontal hip moments in the reconstructed limb were higher than those in the contralateral limb during the stand-to-sit task ( = .010); during squats, sagittal hip angles in the reconstructed limb were higher than those in the contralateral limb ( < .001).

CONCLUSION

Patients after PCLR exhibited compensations at the hip and ankle during downward-driven movements, such as stair descent, squats, and stand-to-sit. Conversely, residual long-term side-to-side differences at the knee were detected during upward-driven movements such as stair ascent and sit-to-stand.

CLINICAL RELEVANCE

After PCLR, side-to-side differences in biomechanical function were activity-dependent and occurred either at the knee or neighboring joints. When referring to the contralateral limb to assess knee function in the reconstructed limb, concentric, upward-driven movements should be prioritized. Compensations at the hip and ankle during downward-driven movements lead to biases in long-term functional assessments.