The psoas muscle is a long, powerful muscle which, in spite of its virtual continuous activity when a person is sitting and walking, is never subject to direct violence and is rarely indirectly traumatized. Strandell1 recently reviewed the literature and cited 13 cases of subcutaneous rupture of the iliopsoas muscle, in 8 of which the rupture occurred in a normal muscle. Haldeman and Soto-Hall2 reported 2 cases of trauma to the psoas muscle in a series of 104 injuries to muscles and tendons. Trauma to the psoas muscle may produce fibrillar, partial or complete rupture of the muscle bundles. The clinical picture depends on the degree of rupture, the site and size of the secondary hemorrhage, the irritation of contiguous nerves and structures and such complications as formation of a cyst, calcification and infection. Strandell has shown that a definite diagnostic picture is obtained, consisting of sudden acute