Leg, the lower limb, or, in the usage of anatomists, that part of the lower extremity which lies between the knee and the ankle. It consists of two bones, the Tibia and Fibula (see SKELETON, FOOT), and of masses of muscles (together with nerves and vessels) which are held in position by coverings of fascia, and are enveloped in the general integument. The shaft of the tibia is of a triangular prismoid form, and presents three surfaces and three borders. The internal surface is smooth, convex, and broader above than below; except at its upper third, it lies directly under the skin, and may be readily traced by the hand. The external and the posterior surfaces are covered by numerous muscles. The muscular mass forming the calf (formed by the gastrocnemius, soleus, and plantaris muscles) is peculiar to man, and is directly connected with his erect attitude and his ordinary mode of progression. The anterior border of the tibia, the most prominent of the three, is popularly known as the shin, and may be traced down to the inner ankle. The fibula, or small bone of the leg, lies on the outer surface of the tibia, and articulates with its upper and lower extremities, and with the astragalus inferiorly. It affords attachments to many of the muscles of this region.
This region is nourished by the anterior and posterior tibial arteries into which the popliteal artery divides. Both these arteries occasionally require to be tied by the surgeon in cases of wounds or aneurism. The blood is returned towards the heart by two sets of veins—the deep, which accompany the arteries, and the superficial, which are known as the internal or long saphenous, and the external or short saphenous veins. These superficial veins are very liable to become permanently dilated or varicose (see VARICOSE VEINS), if there is any impediment to the free transmission of the blood, or even from the mere weight of the ascending column of blood, in persons whose occupation requires continuous standing. The nerves of the leg, both sensory and motor, are derived from the great sciatic nerve and from its terminal branches, the internal popliteal and the external popliteal or peroneal nerve.
In cases of fracture or broken leg the two bones are more frequently broken together than singly, and the most common situation is at the lower third. What is known as Pott's fracture consists of fracture through the lower third of the fibula, with fracture of the projecting lower end of the tibia.
Ulceration of the leg is a frequent consequence of varicose veins, and the very condition which causes the veins to dilate (continuous standing) is an effectual preventative of the healing process, to ensure which complete rest, with the leg raised so as to assist the return of the blood, is necessary.
Bandy, or bow, leg is a condition which may appear as the result of muscular contraction before a child has been placed on its feet. In such a case the natural curve of the tibia is merely exaggerated. It is associated with Rickets (i.e. a deficiency of lime salts), in which the child has the habit of sitting tailor-wise, and thus bending the tibia forwards and outwards in its lower third. Sometimes one leg is bandy and the other in-kneed. This is produced in a soft-boned child by the mother or nurse always carrying the child upon the same arm and using the other arm to clasp the child's legs across the front of her body. See FOOT, KNEE,
HIP-JOINT, CLUB-FOOT, ACHILLES TENDON, &c.; also AMPUTATION, ARTIFICIAL LIMBS.