Variations in torsion of the lower limb in Japanese and caucasians with and without knee osteoarthritis

Objective. Associations between torsion of the lower limb and knee osteoarthritis (OA) appear to be inconsistent across populations. We examined whether femoral and tibiofibular torsion differed between people with and without knee OA (main effect), and whether the differences were consistent across Japanese and Australian Caucasian persons, and between women and men (interaction effect). Methods. Data collection was conducted in Japan and Australia. Subjects with knee OA included 100 Japanese and 102 Australian Caucasians, and healthy subjects included 52 Japanese and 34 Australian Caucasians. Femoral and tibiofibular torsion were measured using reliable clinical techniques. Threeway analysis of variance was conducted to examine the main and interaction effects. Results. While there were no significant differences in femoral and tibiofibular torsion between the subjects with and without knee OA as a whole (main effect), there were significant interactions (p < 0.05). Femoral antetorsion was lower only in the female subjects with knee OA compared with their healthy counterparts (p < 0.05). Tibiofibular torsion was lower only in the Japanese subjects with knee OA compared with their healthy counterparts (p < 0.01). Conclusion. There may be ethnic and sex variations in the relationship between torsion of the lower limb and knee OA; and lower tibiofibular torsion can be a characteristic in a Japanese population with the disease. Longitudinal study is warranted to examine relationships between these variables and knee OA in a population-specific manner to determine whether the observed relationships express cause or effect.