1. A method of detecting and tracking at least one feature associated with an extremity of a user in a three-dimensional scene using depth images of the scene, the method comprising the steps of: a) segmenting at least one region of interest within each depth image; b) determining at least one object of interest that corresponds to a limb of the user within the segmented depth image; c) tracking each limb with respect to time; d) identifying an extremity associated with each limb; e) tracking each identified extremity with respect to time; f) isolating each identified extremity from its associated limb; g) determining parameters relating to each isolated extremity; h) identifying at least one feature in each isolated extremity; and i) tracking each identified feature with respect to time.