Rotational malalignment and femoral torsion in osteoarthritic knees with patellofemoral joint involvement. A CT scan study.

Forty-five osteoarthritic knees in 25 patients with patellofemoral joint involvement were examined preoperatively by computed axial tomography (CT scan) for measurement of femoral torsion, rotation of the knee, and tibial torsion. Rotational alignment of the affected lower extremities was determined as the angle between the femoral neck axis and the transmalleolar axis. The results were compared with a control group of 23 asymptomatic knees. Femoral torsion was significantly lower in the arthritic knees than in the control group (p < 0.05). A compensatory mechanism involving the three components of rotational alignment of the lower extremities in the arthritic knees was identified. Multiple regression analyses using a stepwise method showed that femoral torsion was the first significant predictor in this mechanism. This relationship between femoral torsion and the arthritic knee has not been previously reported.