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Hamstring Strain

A hamstring strain is a condition characterized by partial or complete tearing of one or more of the hamstring muscles located at the back of the thigh and often occur due to an imbalance between the quadriceps and hamstring muscles. These injuries are generally non-contact injuries that occur due to violent eccentric contraction of the muscle.

The hamstrings refer to the semimembraneous and semitendinosous muscles medially, and the long and short heads of the biceps femoris muscle laterally.

These muscles originate from the pelvis and insert into the top of the lower leg bones. The hamstring muscles are responsible for bending the knee and straightening the hip during activity and are predominantly active during running, jumping and kicking.

Hamstring strain anatomy
Hamstring strain anatomy

Hamstring strains range from a grade 1 to a grade 3 tear and are classified as follows:

  • Grade 1: a small number of fibers are torn (less than 5% of muscle fiber disruption) resulting in some pain, but allowing full function.
  • Grade 2: a significant number of fibers are torn Again, pain is present, but there is also loss of knee flexion strength.
  • Grade 3: Complete muscle rupture, including avulsion injury of the ischial tuberosity. This injury presents with severe pain and marked loss of knee flexion strength.

Symptoms

A hamstring injury typically causes a sudden, sharp pain in the back of your thigh. Some describe a "popping or tearing" sensation associated with severe pain. Swelling and tenderness usually develop within a few hours. You may also experience bruising or discoloration along the back of your leg, as well as muscle weakness or an inability to put weight on your injured leg.

If the patient complains of symptoms of numbness, tingling, and distal weakness, further investigation into a sciatic nerve injury (rarely associated with complete tears) or lumbar disc herniation with a resultant S1 radiculopathy is necessary.

Risk factors

Hamstring injury risk factors include:

  • Sports participation: Participation in sports that require sprinting or running, or other activities such as dancing that might require extreme stretching increase the chances of hamstring injury.
  • Muscle imbalance: When the muscles along the front of your thigh - the quadriceps -become stronger and more developed than your hamstring muscles, it increases the chances of injury to your hamstring muscles.
  • Lack of flexibility: Due to lack of flexibility your muscles may not be able to bear the full force of the action required during certain activities.
  • Previous history hamstring injury: If you've had one hamstring injury in past, you're more likely to have another one, particularly if you try to resume all your activities at pre-injury levels of intensity afore your muscles have time to heal and regain strength.


Treatment

Initial

  • The initial management of a hamstring strain consists of the PRICE principle (protection, rest, ice, compression, and elevation).
  • Relative rest and protection may involve weight bearing as tolerated or with higher-grade injuries (grades 2 and 3) cane or crutch walking.
  • Ice massage as often as 20 minutes every 2 hours for the first 48 hours is indicated to limit the amount of pain and swelling.
  • NSAIDs are commonly used to limit the inflammatory reaction and for pain control in the initial days.
Rehabilitation
  • The elements of a hamstring rehabilitation program involve stretching, strengthening, and sports-specific activities. In the acute phase, pain-free range of motion should be achieved as soon as possible. To achieve a full stretch of the hamstring muscle, the hip must be flexed to 90 degrees and the knee fully extended. This stretch is best achieved in the supine position; a towel can be used to facilitate hamstring lengthening(Figure below). It is also critical to improve flexibility throughout the spine and lower extremities.
  • Strengthening exercises are started when the patient is pain free. It is best to start with static contractions and progress to concentric, eccentric, and sports-specific activities as tolerated. Return to sport is allowed when motion is restored and pain free, strength is at least 90% of the uninjured side, and the hamstring/quadriceps strength ratio is symmetric.


Hamstring stretch
Hamstring stretch