Differences from Typical T. pallidicinctus.—It arises from the ventral rather than the ventromedial surface of the lateral iliac process (there is no ventromedial surface to this process).
Individual Variation.—In nearly all of the legs, minute twigs to M. extensor iliofibularis come off the peroneal nerve near the middle of the thigh. The insertional tendon tends toward doubleness in two legs.
M. Piriformis (M. gluteus medius et minimus), [Figs. 16], [20]H, I
T. pallidicinctus
General Description and Relations.—Small, thin, and triangular; lateral to antitrochanter and posterior part of trochanter; deep to M. extensor iliofibularis and posterior (adjacent) to M. gluteus profundus; distal half (or more) tendinous.
Origin.—The muscle arises fleshily from the posterior end of the anterior iliac crest (ventral to the origins of Mm. extensor iliotibialis lateralis and extensor iliofibularis) beginning adjacent to the posterior end of M. gluteus profundus.
Insertion.—The flat tendon narrows, overlaps the anteroproximal corner of insertion of M. flexor ischiofemoralis, and attaches to the lateral surface of the proximal part of the femur immediately anterior to the insertion of M. flexor ischiofemoralis and posterior to the proximal end of M. vastus lateralis; the attachment is posterodistal to the insertion of M. iliotrochantericus medius and posteroproximal to the insertion of M. iliacus.
Innervation.—The small anterior peroneal division of the sciatic nerve turns anteriorly immediately after emerging from the ilio-ischiatic fenestra and passes deep to M. piriformis, giving twigs to the deep surface.
Individual Variation.—In both legs of one specimen, the insertion does not overlap the insertion of M. flexor ischiofemoralis. The posteroproximal corner of the muscle is tendinous in one leg.