Of the muscles, the ilio-psoas is of particular importance surgically, on account of its sheath directing the course of the pus in psoas abscess, where the spine is the seat of disease (q.v.). Being extended over the hip-joint, the muscle is sometimes sprained in violent exercise, while d bursa, which lies under the muscle, between it and the thinnest portion of the hip capsule, may become inflamed, necessitating flexion of the hip to relieve it. This bursa may become enlarged in chronic inflammation, and inflammatory processes in it may affect the pelvis. Contraction of the ilio-psoas muscle and consequent flexion of the hip may be caused by renal and caecal irritation, appendicular abscess especially when situated in the pelvis, psoas abscess, inflammation of the bursa, and hip disease.

Rupture of the adductor muscles is not infrequent, especially in horsemen-rider's sprain consisting of a partial tearing of the muscle close to its pelvic attachment, which is frequently accompanied by a considerable effusion of blood, which may form a hard swelling. Ossification sometimes follows such accidents, a bone-rider's bone-some 1 to 3 inches in length, developing in the tendon of the adductor longus or magnus.

The bturator, or adductor region, of the thigh lies deeply under the base of Scarpa's triangle, being limited by the hip-joint externally, the pubic arch and the perineum internally, the horizontal ramus of the pubis above, and the tuber ischii below. The obturator membrane covers in the foramen, and is covered externally by the obturator externus muscle. In the upper and outer part of the membrane is the aperture Constituting the obturator canal, which, ½ to ¾ inch in breadth, is directed downwards, forwards, and inwards. It is bounded above by the pubic ramus, below by the membrane and the two obturator muscles. Its pelvic orifice is overlaid by parietal pelvic fascia, extraperitoneal tissue, and by the distended bladder, while its orifice on the thigh opens on the deep surface of the pectineus, slightly internal to the femoral vein. The canal lodges some loose fatty tissue, and is traversed by the obturator vessels and nerve, the artery occupying the outer part of the canal, and sending a branch to the hip-joint through the cotyloid notch, and supplying the adductor muscles The nerve arises from the second, third, and fourth lumbar nerves, divides into two branches in the canal, and sends a branch through the cotyloid notch to the hip-joint, supplies the adductor gracilis and obturator externus, and sends a branch to the knee-joint (geniculate branch). A hernia may proceed through the canal, lie beneath the pectineus, and closely simulate a femoral hernia (see Hernia). In addition to the obturator externus and adductor muscles, the gracilis and pectineus form the mass of muscle which occupies this region.