Tibial torsion in patients with medial-type osteoarthrotic knees.

Computed tomography (CT) measurements of torsion of the lower extremities were evaluated in 85 knees of 68 patients with medial-type osteoarthrotic knees and in 24 normal knees of 13 adults. In addition, segmental tibial torsion and CT density of the third lumbar vertebra, reflecting general osteoporosis, were measured. Although there were no differences in the degrees of femoral torsion or knee joint rotation, external tibial torsion in the 68 patients was observed to have a mean value of 11.3 degrees, significantly smaller than the 23.5 degrees observed in the 13 normal adults (p < 0.01). Lateral torsion was 14.1 degrees in mild, 11.9 degrees in moderate, and 7.5 degrees in severe stages of osteoarthrosis. The rate of decrease in lateral tibial torsion was 59.6% in the proximal tibia, 4.2% in the tibial shaft, and 36.2% in the distal tibia. The decrease of lateral tibial torsion was correlated with decrease of CT density of the third lumbar vertebra. There is a correlation between reduction of lateral torsion with the radiographic stage of osteoarthrosis of the knee and general osteoporosity.