The sciatic or ischiatic artery, [a. ischiadica], the largest branch of the internal iliac artery, excepting the gluteal, is distributed to the muscles on the back of the pelvis.

Continuing downwards from the anterior division of the internal iliac artery, it is placed for some distance upon the pelvic surface of the pyriformis muscle and the sacral plexus of nerves, and soon turning backwards beneath the border of that muscle, passes between it and the superior gemellus, and thus escapes from the pelvis, with the great sciatic nerve and the pudic artery, at the lower part of the great sciatic foramen. When on the outside of the pelvis, this artery lies in the interval between the tuber of the ischium and the great trochanter, covered by the gluteus maximus. The sciatic artery gives off several branches to the external rotator muscles of the thigh, on which it lies, and to the great gluteus, which conceals it. Two only of its branches have received special names : viz.,

One, an internal branch, named coccygeal, inclines inwards, and piercing the great sacro-sciatic ligament, reaches the posterior surface of the coccyx, and ramifies in the fat and skin about that bone.
The other named branch (comes nervi ischiadici) runs downwards, accompanying the sciatic nerve, along which it sends a slender vessel.
Some of the branches of this artery are distributed to the capsule of the hip-joint, whilst others, after supplying the contiguous muscle, anastomose with the gluteal, the internal circumflex, and the superior perforating arteries.