Hamstring injuries: anatomy, imaging, and intervention.

Injury to the hamstring muscle complex (HMC) is extremely common in the athletic community. Anatomical and functional aspects of the HMC predispose it to injury, including the fact that the muscles cross two joints and undergo eccentric contraction during the gait cycle. Injury most commonly occurs at the muscle tendon junction but may occur anywhere between the origin and insertion. Complete hamstring avulsions require early surgical repair. The principal indication for imaging is in a triage role to rule out or confirm proximal hamstring avulsion. Acute onset and chronic posterior thigh and buttock pain may relate to pathology at the hamstring origin or muscle tendon junction that can be readily defined on magnetic resonance imaging or, less frequently, ultrasound. Some cases of buttock and thigh pain may relate to spinal pathology. In the elite athlete there is an increasing emphasis on optimizing the rehabilitation process after hamstring injury, to minimize the absence from sports and improve the final outcome. Imaging has a role in confirming the site of injury and characterizing its extent, providing some prognostic information and helping plan treatment. There is increasing interest in the use of growth factors to accelerate healing after muscle and tendon injury. Animal studies have demonstrated clear benefits in terms of accelerated healing. There are various methods of delivery of the growth factors, all involving the release of growth factors from platelets. These include plasma rich in platelets and autologous blood. Clinical studies in humans are very limited at this stage but are promising. At present the World Anti-Doping Authority bans the intramuscular administration of these agents. Other percutaneous injection therapies include the use of Actovegin and Traumeel S and antifibrotic agents.