Knee pain: Understanding the hamstring muscles

Back surgery, Knee pain, Muscle information, Piriformis syndrome, Repetitive strain, Restless leg syndrome (RLS), Sciatic pain, Scoliosis, Structural asymmetry / Sunday, June 28th, 2009

Knowledge is power. The better you understand the muscles of your knee the more empowered you will be to keep them out of pain. The last post discussed the quadriceps in the front of the thigh. The “hamstrings” are in the back of the thigh. Guys refer to them affectionately as “hammies” at the gym.

hamstringsIt’s a funny word and refers specifically to the stringy tendons you feel at the back of your knee. The ham part of the word comes from the old English word for thigh, or hamm. There are four hamstring muscles but only three are technically hamm-strings or muscles of the thigh that attach to tendons. The long head of the outer one (biceps femoris) and the two inner muscles (semitendinosus and semimembranosus) all attach to the bone you sit on (ischium) at one end, and to the bones of the lower leg just below the knee on the other end. The short head of the biceps femoris attaches to the back of the femur and doesn’t have it’s own tendon like the others, so although it’s included in the list of four, it is not regarded as a “true hamstring.”

The hamstring muscles act primarily to bend the limb at the knee and extend the limb backward at the hip. Climbing stairs, they bend your knee to raise your foot onto a step, then they work again at the end of straightening your leg. In the meantime they stabilize the knee as the quads contract to raise you to the next step. They also act with the glutes and low back erectors to keep you standing up straight. They are always active when you are bending forward. Even raising your arms or a head-forward posture will activate them. Tune in to the back of your thighs and try each of these moves to feel what they do.

As a Neuromuscular Therapist (Boston area), I am also fascinated by Trigger Points. Regarding knee pain, all hamstring muscles refer to the back of the knee, but the biceps femoris TrP on the outside is more significant with it’s deep aching pain. Hamstring Trigger Points can make walking difficult, sitting painful and sleep nonrestful. Tension can make the opposing quads weak or can cause development of TrPs there which won’t resolve until hamstring TrPs have been treated. The quads and hams work together and both must be treated and stretched to relieve pain in the knee.

Knee pain from the hamstring muscles can be caused by or perpetuated by 1) overload in sports or when catching yourself from falling, 2) overuse or repetitive use without sufficient stretching, 3) compression as from crossing your legs or sitting with your thigh pressed against the edge of a chair seat, 4) prolonged shortening as from driving or sitting too long, 5) Trigger Point referrals from 8 other muscles, 6) nerve root irritation as from disc herniation, or from spinal fusion or scoliosis or asymmetry that tilts the pelvis to one side at L5/S1, or from leftover Trigger Points from a laminectomy surgery,  7) sciatic nerve irritation as from piriformis syndrome and 8) structural asymmetries such as uneven pelvic bones or short arms that make you lean forward onto your thighs or cross your legs.

So we have discussed the two major muscle groups that cause knee pain, but there are small muscles that can be just as troublesome. Next we will go over the little popliteus and plantaris muscles at the back of the knee.

Therapist tips: 1) If you treat chronic hamstring tension, watch out for reactive shortening in the quads. 2) If the hamstrings are always tight, the glutes will be weak. 3) The symptoms of Restless Leg Syndrome can be caused by pressure on the hamstrings. 4) Treat the adductor magnus for adhesions to the hamstrings.