A hamstring strain, often called a pulled hamstring, is a common injury to one or more of the hamstring muscles, during which muscle or tendon fibers are stretched, or partially or completely torn. These injuries are graded according to severity, with Grade 1 being mild, Grade 2 being moderate, and Grade 3 being severe, with a complete rupture.
The hamstring muscle group consists of three muscles: the semitendinosus, semimembranosus, and the biceps femoris. These muscles originate from the lower edge of the pelvis at a part called the ischial tuberosity. They travel down the back of the thigh, across the knee and attach to the tibia and fibula, the bones of the lower leg. At each end of the muscles are tendons, strong cords of connective tissue. Tendon fibers begin within the muscle fibers and extend to the bones where they have their attachments. A hamstring injury can happen at any point along the muscle: at the origin; where the tendon and muscle fibers join; in the belly of the muscle; or where the muscle inserts into bone.
The function of the hamstrings is to allow you to extend your leg straight back, and also to help you bend your knee.
Hamstring strains are almost always caused as a result of overloading. This means stretching the muscle while at the same time loading it with weight and force necessary for motion. An example of loading the hamstrings is an athlete sprinting: the rear leg is straight and the toes push against the ground. In this situation the hamstrings are stretched (to allow the straight leg) and loaded with body weight and the force needed to propel the body forward.
Overloading the muscle, or subjecting it to too much force, can cause a hamstring strain. For this reason, athletes are particularly prone to this injury. Adolescent athletes are also at risk, due to the fact that muscles and bones do not develop at the same rate. If the bone has grown faster, the hamstring will be tight and therefore vulnerable.
Poorly conditioned, tired, or tight hamstring muscles are more likely to be injured. Often, a person’s quadriceps muscles, in the front of the thigh, are stronger than their hamstrings, so the hamstrings will tire faster, increasing the risk of injury.
Symptoms of a hamstring strain will depend somewhat on the severity of the injury, but may include the following:
- Sudden, severe pain in the back of the thigh, causing you to stop immediately. You may hop or fall down, unwilling to put weight on the injured leg.
- Possible popping or snapping sensation at moment of injury.
- Swelling, the extent of which will depend on your injury.
- Bruising on the back of the leg, below the knee.
- Tenderness over the injured area.
- Weak hamstring muscles.
Your doctor will ask you about your medical history, including any previous injuries to your leg. He or she will also ask you about the circumstances of your current injury and the type and severity of your symptoms. You will have a physical examination, during which the doctor will palpate (touch) your leg to assess areas of tenderness. Depending on your particular injury, you may be asked to lie on your front and bend your knee against resistance. This may cause pain.
An X-ray may be taken to see if the hamstring injury has torn away a small piece of bone. This can sometimes happen with a severe strain, and is known as a tendon avulsion. These normally occur at the upper (proximal) end of the muscle rather than the lower (distal).
Magnetic resonance imaging (MRI) scans may be taken as these are better than X-rays at showing soft tissues such as muscles and tendons. MRIs are therefore often used to evaluate the extent of the injury and aid decisions regarding treatment.
Early treatment for a hamstring strain has been shown to provide the quickest and best recovery. It is extremely important to follow medical advice and allow yourself time to heal otherwise you will be at risk of recurrent hamstring injuries.
Most hamstring strains heal with conservative (non-surgical) treatment, resulting in a full recovery and a return to normal, pre-injury levels of activity. A mild Grade 1 strain will heal swiftly, whereas a Grade 3 injury, which may require surgical repair, might take 3 to 6 months to heal properly.
During the acute stage of the injury, that is, the first one to five days, the strain can be treated with the following methods:
Rest: Avoid any activity that either caused the injury or makes your symptoms worse. You may wish to use crutches temporarily, to keep weight off your injured leg. Your doctor may recommend that you wear a knee splint for a while. This would prevent your leg fully straightening, thereby avoiding any further strain on the hamstrings.
Ice: Ice, crushed in a bag and wrapped in a towel, can be applied to the back of the thigh for as long as is comfortable, several times a day. This will help to reduce swelling and pain.
Compression: Wearing a compression bandage on your leg will prevent excessive swelling and minimize bruising.
Elevation: Raising your leg above the level of your heart will help reduce swelling. This will be most easily achieved at night, when you can rest your leg on a pile of pillows while you sleep.
NSAIDs: Over-the-counter non-steroidal anti-inflammatory medications will help relieve pain and swelling.
Physical therapy: When advised by your doctor, a graduated program of exercises can be initiated, beginning with gentle stretching and gradually including strengthening exercises. Always follow medical advice as to when it is safe to begin exercising, and when you can return to sporting activities. Physical therapy might include massage to align muscle and tendon fibers so that they heal in the correct position. This also minimizes the formation of scar tissue.
A Grade 3 strain may require surgical repair. If the injury is a tendon avulsion, where the tendon has pulled away a piece of bone as it ruptured, surgery will always be required. Your surgeon would reposition any bone fragment or tendon or muscle fibers, and hold them in place with surgical stitches or staples. After surgery you would need to avoid putting weight on the leg. You may have to wear a brace and use crutches to help you get around until the injury has fully healed.