What Are the Hamstrings?
The hamstrings are a collection of three muscles located in the back of the thigh that are responsible for bending, or flexing, the knee. The three are the semitendinosus, the semimembranosus, and the biceps femoris muscles that begin as a tendon that inserts in the ischium, one of the pelvic bones, and run the length of the femur (the thighbone), crossing the back of the knee to attach to the tibia and fibula. A small portion of the hamstring muscle also spans across the hip joint and is involved in hip extension. The hamstring muscle fibers gradually become tendon fibers near the knee to attach to bone. One can appreciate the thick tendon bands when feeling behind the knee joint.
The hamstring muscle is balanced by the quadriceps muscles on the front of the thigh that cause the knee to extend. Together the hamstrings and the quadriceps help control power and stability of the knee joint, allowing activities like walking, running, jumping, and squatting.
Medically Reviewed by a Doctor on 12/11/2015
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