Asymmetric knee loading in advanced unilateral hip osteoarthritis.

Objective: Subjects with unilateral end-stage hip osteoarthritis (OA) who undergo total hip replacement (THR) preferentially require subsequent replacement of the contralateral knee compared with the ipsilateral knee. We investigated whether this nonrandom, preferential evolution of lower extremity OA from the hip to the contralateral knee joint may be related to asymmetries in dynamic joint loading at the knees, particularly the peak external knee adduction moment, which has been associated with the progression of knee OA.

Methods: Gait analysis was performed on 50 subjects who were preoperative for unilateral THR. Twenty-two of these subjects were reevaluated postoperatively 10-23 months after undergoing successful THR. At each analysis, dynamic joint loads in the contralateral knee were compared with those in the ipsilateral knee.

Results: Prior to THR, the peak external knee adduction moment and peak medial compartment load were significantly higher in the contralateral knee. This asymmetry persisted after THR.

Conclusion: Subjects with unilateral end-stage hip OA preferentially require subsequent replacement of the contralateral knee, as compared with the ipsilateral knee. Among patients with unilateral end-stage hip OA, the contralateral knee is subjected to higher dynamic joint loads than is the ipsilateral knee, and this asymmetric loading persists long after subjects have undergone successful THR. Biomechanical factors appear to be involved in the multiarticular evolution of OA of the lower extremities.