The hamstrings are a group of muscles located on the back of the upper leg (thigh). The muscles of the hamstrings include the biceps femoris, semitendinosus and semimembranosus. The proximal ends of the hamstring muscles originate from the ischial tuberosity in the rear of the pelvis.
The muscles of the hamstring are all innervated by the sciatic nerve. The hamstring muscles are the major flexors of the knee and also aid in hip extension.
Injuries to the hamstring muscles primarily occur proximally and are a common source of chronic pain and injury in athletes. It is often referred to as hurdler’s injury, athletes who attempt to clear hurdles are prone to injury due to excessive hamstring tension.
Hamstring strains are classified into three grades: minor tears within the muscle, partial tear within the muscle, and complete muscle tear.
Most hamstring injuries in adults will occur at the musculocutaneous junction but injury may also occur at the insertion into the ischial tuberosity.
Severe hamstring injuries where the tendon tears away with a fragment of bone are called avulsion injuries. Avulsion injuries are not common and typically occur in patients who are younger, skeletally immature athletes.
The patient will have a sharp pain in the back of the thigh (popping or tearing of the muscle). An ecchymosis of the posterior thigh may also be present along with a palpable mass in the middle of the thigh. It is usually diagnosed by an MRI.
A strained or pulled hamstring can occur due to an insufficient warm up time before an activity. The patient should have treatment consisting of rest, ice, a compression bandage, elevation and possible physical therapy.
Surgery will be done in complete avulsion injuries with muscle retraction; the surgery is usually done early. The incision will be made, the muscle is then located. The nerve will need to be protected. Anchors will be used in the ischium to repair the tendon to the tuberosity. In cases of a bony avulsion, screws may be used in severe cases.