_Shape._—Triangular in shape, it is aponeurotic anteriorly and more fleshy posteriorly. _Relations._—Anteriorly, covers over the posterior portion of the sartorius and the body of the gluteus medius; posteriorly, bordered by the semitendinosus and the biceps. _Action._—Abducts the thigh. =Gluteus Medius= (Fig. 24, No. 11). _Location._—Supero-anterior part of the ilium under the gluteus primus. _Origin._—From the entire supero-internal margin of the pre-acetabular surface of the ilium and the concave surface on the adjacent bone. _Insertion._—By a strong tendon which passes over a bursa on the anterior rim of the trochanter and is inserted obliquely to this trochanter. _Shape._—A fleshy muscle filling the concavity of the pre-acetabular division of the ilium. _Relations._—Superiorly, with the gluteus primus; inferiorly, with the gluteus minimus. _Action._—Abducts and pulls the femur forward. =Gluteus Minimus= (Fig. 24, No. 12). (Synonym.—Gluteus profundus.) _Location._—Beneath the medius and the smaller of the two. _Origin._—To the anterior margin of the outer border of the ilium, and from the supero-external surface of the last rib. _Insertion._—The fibers extending downward and backward and outward become tendinous and are inserted below the trochanter of the outer part of the upper third of the femur. _Shape._—Small, fleshy. _Relations._—Inferiorly, with the bone and superiorly, with the gluteus medius. _Action._—Abducts and pulls the thigh forward. =Extensor Femoris= (Fig. 24, No. 15). _Location._—Anterior femoral region. It is divided into two parts: the vastus externus and the crureus. _Origin._—The vastus extemus (Fig. 24, No. 14) arises tendinous from the base of the trochanter of the outer part of the femur and from this point down the bone approximately to the condyle. The crureus (Fig. 24, No. 13) originates by a tendon from the anterior upper prominent rim of the trochanter, from this point extending down the antero-external part of the shaft of the femur. _Insertion._—Merges with the gluteus primus, and, by a fascia-like arrangement, spreads over the front of the knee-joint inserts to the patella and is also inserted into the crest of the tibia. _Shape._—Large, fleshy. _Relations._—Posteriorly, with the femur and anteriorly, with the sartorius. _Action._—Extends strongly the leg upon the thigh. =Vastus Internus= (Fig. 16, No. 3). _Location._—Internal and lateral side of the femur. _Origin._—From the postero-internal part of the shaft of the femur just below the head, and in a straight line extending down the femur. _Insertion._—By a broad tendon along the thickened inner border of the summit of the tibia. _Shape._—Thick, long. _Relations._—Anteriorly, with the bone; surrounded by the other crural muscles. _Action._—Extends the leg upon the knee; a powerful assistant of the extensor femoris. =Biceps Flexor Cruris= (Fig. 17, No. D, 1). _Location._—Posterior tibial region.