In fact, all the traffic around two mutually perpendicular axes, as well as around the intermediate axis (limited circumducts - in the hip joint) are strictly determined specific matching articular surfaces scapula - shoulder and pelvis - hip.
The largest scale motion has the hip joint, but the movement is permitted by that joint, due to low prevalence as the area of the femoral head over that of acetabulum of the pelvis, specifically combined for each of the two major phases of limb movement. For example, flexion in the hip joint accompanied by abduction and supination, extension - abduction and pronation. An example of the close interdependence between the various joints of the limbs may be an elbow and knee joints, extension (or flexion), which immediately causes the extension (or flexion), and at the same number of degrees in the downstream joints.
Respectively, are coordinated among themselves and the muscles acting on the joints of the extremities and particularly the specialized muscle, tendon turned into strands or bundles are automatically called, for example, changing the angles of joints are located below, under the influence of flexion or extension in prokeimalnyh joints.
It is also noteworthy specialization number of joint surfaces in the direction of their acquisition of an irregular curved (humcrus, the screw of the talus).
The maximum voltage of collateral ligaments in the transition (between flexion and extension) position saves the muscle energy needed, for example, to hold the limb to straighten the state.
Thus, the transition to odnopalosti the horse kind of automation of the limbs occurred due to the narrowing of their functions with parallel morphological and functional substitution of the musculoskeletal system (the prevalence of passive connective tissue elements of the active muscle). As a result of these changes, limb horses purchased a limited fatigue while driving and a full (front limb) or almost complete (hind limb) indefatigability on standing.
This conclusion leads the analysis of skeletal-muscle and tendon-ligament apparatus of finite horse, a detailed acquaintance with which is of exceptional interest.