Rotational alignment of the lower limb in osteoarthritis of the knee.

Rotational alignement of the lower limbs in 43 patients with osteoarthritis of the knee was measured by computerized tomography. Eighty-four limbs were classified in three subsets, patello-femoral osteoarthritis (subset P), medial femorotibial osteoarthritis (subset M) and lateral femorotibial osteoarthritis (subset L). The femorotibial angle of subset M was 5 degrees greater than that of subset P on the average. Femoral torsion of subset P was significantly greater than that of subset M. Femoral torsion in osteoarthritis of the knee was correlated with external tibial torsion and external torsion of the leg, which included both external rotation at the knee and external tibial torsion. External torsion of the leg in subset M was less than normal and rotational alignment of subset P was also outside the normal range. Our findings show that the frontal and rotational alignment of the lower limb are aetiological factors in osteoarthritis of the knee.