The lower limb in its basic structure is similar to the upper limb because both of them formerly (as in animals) were used for locomotion. Each limb has a girdle, hip girdle for lower limb or shoulder girdle for upper limb, by which it is attached to the axial skeleton. The girdle supports three main segments of the limb, a proximal thigh or arm, a middle leg or forearm and a distal foot or hand. The similarity between the two limbs is not only outward, but to a great extent it is also found in the bones, joints, muscles, vessels, nerves and lymphatics. However, with the evolution of erect or plantigrade posture in man, the two limbs despite their basic similarities have become specialized in different directions to meet the new functional needs. The emancipated upper limb is specialized for prehension and free mobility whereas the lower limb is specialized for support and locomotion. In general, the lower limbs attain stability at the cost of some mobility, and the upper limbs attain freedom of mobility at the cost of some stability. Thus the lower limbs are bulkier and stronger than the upper limbs (Fig. 1.1). A few of the distinguishing features of the lower limbs are listed below mtlv

Compare structural anatomy of upper vs lower limbs