Imaging of the hamstrings.

The hamstring muscles, located in the posterior thigh, include the biceps femoris, the semimembranosus, and the semitendinosus. The proximal portions of the hamstring muscles are subject to a variety of injuries and pathology. Many of these entities affect the origin of the hamstrings, including the tendinous enthesis, the underlying ischial tuberosity, and the surrounding tissues. Tendinosis and small partial tears at the origin are the result of chronic attrition. They may be accompanied by bursitis or hamstring syndrome. Apophysitis occurs in teenagers prior to complete fusion of the ischial apophysis and results from repeated traction injuries on the apophysis without discrete displacement. Abrupt injury at the origin from forced flexion of the hip results in osseous avulsions of the apophysis in teenagers and proximal tendon ruptures in adults. Other entities affect the muscles distal to the tendon origins. These injuries include strains and partial tears of the musculotendinous junction from acute indirect trauma, delayed onset muscle soreness from overuse of the muscle group without discrete remembered injury, and contusions and myositis ossificans from direct blunt impact. The imaging features of these injuries and pathology are fairly specific and diagnostic, with the exception of some cases of myositis ossificans and chronic ischial avulsions.