Motion of the cat hind limb during non-weightbearing movements is determined by muscular, inertial, and gravitational moments. To understand how the central nervous system controls limb motions, both muscular and non-muscular moment contributions to limb dynamics must be quantified. In this study, a method was presented for quantifying cat hind limb dynamics using a two-link rigid body model of leg and paw, and equations of motion which parcelled out the relative contributions of muscular, inertial, and gravitational moments to net joint moments. Modulations in muscular and non-muscular components of knee and ankle joint moments were examined during two different behaviors:​ 1) swing phase of locomotion (Part II) at two treadmill speeds using three gaits:​ pace-like walk and trot-like walk, at 1.0 m/s, and gallop, at 2.1 m/s, and 2) paw-shake response (PSR) (Part III) in cordotomized cats, a rapid, alternating flexion and extension of hind limb joints elicited by placing tape on the paw. Kinetic results showed that muscle and segmental interactive moments significantly affected limb trajectories during swing phase and PSR. Gait mode and speed of locomotion were significant determinants of limb dynamics during swing phase. Moment magnitudes typically were greater for pace-like walk than for trot-like walk at the same speed. Some moment components were greater in galloping than in walking. Generally, across gaits, the net and muscle moments were out of phase with proximal joint motion, and were in phase with distal joint motion. Stable hind limb oscillations emerged during PSR from the interaction between a regular pattern of muscle activation and motion dependent limb dynamics. During stable hind limb oscillations, muscle moments functioned to decelerate and reverse joint motions. At the proximal joint, substantial inertial loading due to paw motion was com pensated by large magnitudes of the knee muscle moment. Ankle muscle moment dominated distal joint dynamics, but inertial interaction between segments augmented paw motion and increased the effective ness of the PSR.