Functional significance of torsion of the tendon of tibialis posterior.

The authors describe the anatomical necessity and functional significance of torsion of the tendon of tibialis posterior. A wooden model of the right lower extremity has been constructed which includes representations of the ankle, subtalar, and oblique midtarsal joints. The model is used to show that the presence of torsion within the tendon of tibialis posterior eliminates the need for any longitudinal slippage between individual tendon fibers during triplane movement of the joints of the lower extremity.