The talus is are of the most important bones of the foot because it support and distributes the body forces above it. It allow motion between the tibia and the foot and forms the important articulations with tibia superiorly, with the calcaneous inferiorly (the subtalar joint), and with the navicular anteriorly.The muscles of the ankle and foot include both extrinsic and intrinsic muscles. The extrinsic muscles are organized into an anterior group that drosiflexes the ankle and extend the toos, a posterior group that produce planter flexion of the ankle and flexion of the toes, and a lateral group that pronates the foot. Most of these muscles cross several jounts of the foot.Most of the joints of the foot are hing or gliding joints, but their alignement produces triplaner motion as pronation and supination. The joint of the ankle, hind foot, and mid foot can pronate together, making the foot more flexible, or supinate together to increase the rigidity of the foot. These movements are essential to the normal loading and unloading of the foot.Biomechanics uses physics and engineering concepts to describe the motion undergone by the various body segments and forces acting on these body parts during normal activities.Biomechanics of the joint is divided into kinematics that deal with motion of a body without reference to force or mass at includes rang of motion and surface joint motion, and kinetics that deal with the motion of a body under the action of given forces and/or moments, it include statics and dynamics behavior of the joints.Habitual bipedal locomotion is a uniquely human function and influences an individual’s participation and interaction in society. Impairment in gait are frequent complaints so, physicians require a firm understanding of the basic mechanics of normal locomotion to determine the links between impairment of discrete segments of the musculoskeletal system and the patient’s abnormal movement patterns in gait.