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 strains range from a grade 1 to a grade 3 tear and are classified as follows:
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.
Hamstring injury risk factors include: