A method to determine the range of motion of the ankle joint complex, in vivo.

The purpose of this investigation was to develop a method to quantify a range of motion of the ankle joint complex (AJC) in vivo. A six-degree-of-freedom apparatus was constructed to measure the unconstrained active range of motion of the AJC. Extensive tests evaluating the accuracy of the fixture and data collection protocol were conducted. Euler angles similar to dorsiflexion-plantarflexion, eversion-inversion, and abduction-adduction were used to quantify the range of motion. Significantly greater (p < 0.05) values were found for plantarflexion, inversion, and abduction of a young group of male subjects (n = 7) compared to an elderly group of male subjects (n = 10). In addition, maximum range of motion values did not necessarily occur from the neutral position. In future, this method can be used to help investigate the relationships between AJC motion and injury, changes in range of motion as a function of age, and design of prosthetic ankle joints.