Background: The purpose of the present study was to determine the validity and reliability of using ultrasound to measure tibial and femoral torsion.

Methods: In vitro ultrasound measurements of torsion in 118 matched dried tibiae and femora were compared with direct anatomical measurements with use of simple regression. The second part of the study involved repeated in vivo ultrasound measurements made on twenty adult limbs to determine the clinical reliability of our methods.

Results: The in vitro ultrasound measurements of femoral and tibial torsion were significantly related to the anatomical measurements (p < 0.001 for both). The inter-rater correlation coefficients between three examiners were 0.84 for both the tibial and femoral measurements, and the intra-rater correlation coefficients ranged from 0.86 to 0.98. The in vivo measurements were similar to the in vitro measurements, and the intra-rater correlation coefficients for repeated measures were 0.91 and 0.93 for femoral and tibial torsion, respectively.

Conclusions: Ultrasound is a viable tool for measuring torsion of the tibia and femur. In order to minimize measurement errors, the ultrasound measurement should be used to calculate the predicted value of torsion with use of the regression equation.

Clinical Relevance: Abnormal torsion in the tibia and femur have been linked to osteoarthritis in the knee. Precise, safe, and quick measurements of torsion are needed for clinical decision-making and for use in long-term studies.