Instrumented measurement of human joint motion.

Accurate measurement of human joint motion is essential to the design and evaluation of internal joint prostheses and artificial limb replacements. A triaxial electrogoniometer instrumented by three miniature precision potentiometers was developed to fulfill this task. A special linkage was used to attach this apparatus externally to the joint. Three-dimensional angular motion following the classical Eulerian angle definition was measured in real time. The error due to exoskeletal attachment was corrected by the method of 4 x 4 matrix. This technique is now being routinely used for objective functional evaluation on the patients with abnormal hip, knee and ankle joints as well as lower extremity amputees fitted with artificial limbs.