Definition of a subject-specific model of the knee in vivo

Kinematic models of the knee are useful for applications aimed at replicating or restoring the natural motion of the joint, such as prosthesis design and definition of lower-limb musculo-skeletal models for gait analysis. Several of these kinematic models were proposed based on generic geometries, but there is an increasing request of accurate subject-specific models to be personalized on the single patient under analysis. Spatial parallel mechanisms with one degree of freedom [1,2] are subject-specific models that replicate the knee natural motion in vitro with a high accuracy, but their definition in vivo requires particular attention. In the present study, a complete procedure is presented to define these models in vivo, and is applied on a volunteer to replicate its knee joint motion.