Tibial torsion: significance and measurement.

Following the acceptance for publication of the article by Hazlewood et al. in a recent issue of Gait & Posture we were invited by the Editor in Chief to comment on the challenging issue of measuring tibial torsion [1]. Tibial torsion describes the axial or transverse plane alignment of the shank segment of the lower extremity. In utero, lower extremity limb bud formation occurs during the 4th week of gestation [2,3]. During the 7th week there is medial rotation of the developing lower extremity, bringing the great toe to the midline. Lateral or external rotation then occurs slowly throughout the remainder of the growth and development years until skeletal maturity. Clinicians may describe tibial torsion based upon anatomical landmarks about the knee, ankle and foot [4–7]. At the knee, the long axis of the thigh, the patella, and the tibial tubercle have all been utilized to estimate the orientation of the flexion extension axis of the knee joint. At the ankle, the medial and lateral malleoli, the hindfoot, and the long axis of the foot have all been utilized to estimate the orientation of the plantar flexion-dorsiflexion axis of the ankle joint. The anatomical definition of tibial torsion is not precise, and there is poor consensus concerning the optimal technique for its clinical assessment [8,9]. Based upon assessment of the alignment of the bimalleolar axis relative to the longitudinal axis of the thigh, it has been determined that tibial torsion is approximately 58 external at birth, with progressive external rotation to 158 by skeletal maturity [4]. Utilizing the orientation of the bimalleolar axis relative to the flexion-extension axis of the knee, it has been determined that the tibia is 208 externally rotated when the knee is flexed to 908, and rotates to 408 external as the knee is fully extended [10]. Dynamic internal rotation of the tibia relative to the femur as the knee flexes contributes to the femoral roll back mechanism [10]. Dynamic external rotation of the tibia relative to the femur as the knee extends contributes to joint stability [10]. At the ankle, dynamic external rotation of the tibia occurs during the loading response, which unlocks the hindfoot and midfoot joints, promoting shock absorption function [11–13]. Dynamic internal rotation of the tibia occurs during the remainder of the stance phase, which locks the hindfoot and midfoot joints,