|Discussion: Hamstring injuries are common injuries that tend to heal slowly. Once injury occurs, the patient is at high risk for recurrence. The hamstring muscles include the semitendinosus, semimembranosus, and biceps femoris. The semitendinosus originates at the ischial tuberosity and inserts at the pes anserine; the semimembranosus originates at the ischial tuberosity and inserts at the posterior medial tibia. The biceps femoris has a long head that originates at the ischial tuberosity and a short head at the posterolateral femur and inserts into the head of the fibula. Both muscles serve as knee flexors and hip extensors. Biceps femoris is most commonly injuried.|
Hamstring strain is a noncontact injury and usually occurs with either acute or insidious onset. Strain injuries frequently are seen in athletes who run, jump, and kick. Avulsion injuries are seen in patients who participate in water-skiing, dancing, weight lifting, and ice-skating. The avulsion injury usually follows a burst of speed, and the patient may report a popping or tearing sensation. The most commonly affected muscle area in the hamstring complex is the short head of the biceps femoris, possibly because of its innervation.
As with most strain injuries, the injury can occur at the following 4 places: Origin of the muscle, musculotendinous junction, muscle belly or insertion of the muscle. Injury is most likely to occur while the musculotendinous junction undergoes maximum strain during eccentric contraction of the hamstrings. Hamstring injuries are graded
1: Mild strain with few muscle fibers being torn
2: Moderate strain with a definite loss in strength
3: Complete tear of the hamstrings
Acute and chronic injuries may be seen on radiographs, but often plain films are not helpful and avulsion fracture may not be seen if present. Calcifications may be seen with acute avulsion fracture or with chronic injury. MRI is most sensitive.