Hamstring injuries usually occur with sudden lunging, running, or jumping, resulting in muscle injury. The sudden jerking pulls on the tissues of the hamstring muscle. In fact, it is commonly referred to as a "pulled hamstring." Oftentimes, a "pop" is heard or felt by the injured athlete. A variable amount of pain is experienced immediately. The athlete is usually unable to continue and oftentimes cannot even stand.
Examination of the individual with a hamstring injury reveals spasm, tightness, and tenderness. With more severe injury, swelling and a black and blue or bruised appearance will follow. In some cases, a palpable defect (detectable by touching) will be present in the muscle. Tears and strains most often occur at the middle of the back of the thigh where the muscle joins its tendon or at the origin of the hamstring at the base of the buttocks (at the ischium).