Forward propulsion in locomotion is mainly brought about by the action of pelvic limbs. Hence, they are stronger, more muscular, particularly with regard to the development of hip and stifle joints. The sacrum and pelvis are attached by means of sacro-iliac joint (amphiarthrosis) i.e the sacrum is suspended on the medial surface of the wings of ilium. This helps in effective transmission of thrust of the hind limb to the trunk. From the trunk, the entire load is transmitted to the pectoral limbs.
The principle muscle contraction in the hind limb during locomotion is similar to that of thoracic limb. The pelvic limb is raised off the ground by the flexion of all the joints of hind limb (swing phase). Then the flexed limb is moved forward by the contraction of tensor fascia latae, superficial gluteus, sartorius and ilio-pasoas muscles. During this time the limb is abducted. Then the limb is adducted by the adductor muscles on the medial aspect of thigh (pectineus, gracillis and sartorius).
Then the stance phase begins by the extension of all the joints. During this phase, the body is propelled forward by the contraction of extensors of hip (middle gluteus), stifle (quadriceps femoris) and the hock (gastrocnemius).
Movement of the whole body of the animal results from the co-ordinated movement of the individual body parts. This may be forward, sideward or backward movement of the body. Some movement occur without change in location of the animal like sitting, lying down, rolling and rising.
