Joint center longitudinal positions computed from a selected subset of Chandler's data.

Mathematical models of the human body are indispensable tools for studying the biomechanics of human movement. The geometrical centers of the 12 main joints (shoulders, elbows, wrists, hips, knees ankles), modeled as simple mechanical joints, are widely used as reference points for building mathematical models of the human body. These reference points, typically defined as "joint centers", are assumed to maintain a fixed 3D position relative to both the segments forming the joint, throughout the range of joint motion. No single point in a human joint perfectly meets this assumption, and no simple method is available for locating the points that are closest to meet it. Researchers often have recourse to subjective methods, based on their knowledge of anatomy. Objective estimates are easily attainable if the positions of a few bony landmarks can be measured on the subject, and the longitudinal distances of the joint centers from these landmarks are known. A subset of the anthropometric measurements performed by Chandler et al. (NTIS No. AD 710-622, 1975) on six cadavers was critically selected and utilized to compute the percent longitudinal distances of the 12 main joint centers from neighboring bony landmarks, relative to the lengths of the respective proximal and/or distal segments. Three-dimensional positions are attainable as well, by assuming joint centers lay on the respective segment longitudinal axes. The use of a method for accurately locating joint centers is recommended, particularly when they are used as reference points for defining a personalized geometrical model of a subject's body.