In-vivo identification of a subject-specific model of the knee natural motion

Kinematic models of the knee are useful for the applications aimed at replicating or restoring the natural motion behavior of the joint, such as gait analysis, lowerlimb modeling, joint prosthesis design. Several kinematic models were proposed in the literature, starting from the basic hinge, to more sophisticated mechanisms. The geometry of these models can be defined also from average data in the literature. However, there is an increasing request of subject-specific models to be personalized on the specific single patient joint. In general, more detailed models allow a better representation of the joint motion, but their identification on single patients requires more attention. In particular, spatial parallel mechanisms with one degree of freedom [1,2] are sophisticated models which proved to be very accurate for the replication of the natural motion of knee specimens in vitro. In the present study a complete procedure is presented which shows that, by accurate experimental measurements and data processing, these models can also be personalized on living subjects to replicate original joint motion.