Hamstring muscle Injury

Overview

Hamstring muscle injury is most common sport injury. This muscle is present on the back of the thigh spanning from hip to knee. It is a group of muscles consisting of three muscles; semitendinosus (ST) semimembranosus (SM), and the long head of the biceps femoris (LHBF).

Hamstring injury is most common cause of injury absence in some sports like football, soccer, running and jumping and other field sports. It accounts for approximately 35-40-% muscle injuries in soccer.

Mechanism of Injury:

Two common mechanisms implicated are a high speed running and overstretching of the muscle. Running related hamstring strains (type I strains) generally involve the long head of biceps femoris near its muscle-tendon junction in lower thigh (pain occurs near knee). Overstretching of the muscle (type II strains) may occur in movements that simultaneously involve hip flexion and knee extension (thus placing the muscle in a position of extreme stretch) such as kicking or dancing. The stretching-type hamstring injury typically involves the proximal part of semimembranosus (pain occurs on the buttock).

Risk Factors:

Most common risk factor is history of previous injury which makes the athlete prone to injury again. Some sports which involve kicking movement and running like football, Judo, sprints, etc. are high risk sports for hamstring injury.

Diagnosis

X ray may be required in children because a small piece of bone may be pulled apart along with muscle tendon (avulsion fracture). MRI is the investigation of choice to diagnose or rule out hamstring strain or tear. It should be done within one to three days of injury.

Treatment

Treatment immediately after a muscle strain consists of RICE (rest, ice, compression and elevation) therapy. Most of the hamstring muscle injuries are strain to partial tear and can be treated non surgically with conservative treatment. In children surgery may be required for proximal avulsion fracture (a piece of hip bone is pulled along with tendon), which should be fixed for best results. Surgery may also be required in adults where muscle tendon is retracted after tear.

Once the patient becomes pain free, rehabilitation program is started which include stretching, and strengthening   exercises of hamstring muscle. For full recovery, this should be followed by core muscles strengthening exercises. Optimal rehabilitation program is very important as re-injury rate is very high. Proximal injuries (near hip) take longer time to recover than distal injuries (near knee). On an average athlete may take 2 weeks to 4 months to get back to sports depending on severity of hamstring injury.