I often see bodybuilders, recreational trainees, track athletes, football players and other athletes who complain of pain in the back of their thighs.  These patients usually call and say “I strained my hamstring, but the funny thing is it isn’t getting better”.   This is a telling comment.   Sometimes the injury the patient describes isn’t a simple hamstring strain.

First, it is important to understand the true hamstring injury.  The hamstring muscles are located in the back of the thigh.  There are three muscles that comprise the hamstrings: biceps femoris (outer or lateral hamstring), semimembranosus (central hamstring), and semitendinosus (inner or medial hamstring).  All three hamstrings originate (attach) on a large bony prominence on the bottom of the pelvis (ischial tuberosity).  The biceps femoris inserts (attaches) onto the top of the outer, lower leg bone (fibula).  The semimembranosus inserts into the top, back of the large lower leg bone (tibia) and the semitendinosus inserts into the inner, or medial side of the top of the tibia. 

The collective hamstring muscles have two main functions: 1) flexing, or bending the knee as if performing a leg curl; 2) extending or straightening the hip as if performing hyperextensions, good mornings, Romanian deadlifts or stiff-legged deadlifts.  The traditional leg curl when performed laying face down on a flat bench does not stretch the hamstring at the knee and the hip, so it does not rank as a very efficient exercise.  The exercises in which the knee is kept straight and the hip is bent (flexed) and straightened (extended) such as the Romanian deadlifts, etc. mentioned above, above are more effective hamstring exercises because the muscle is stretched at both joints.

Muscles are most often strained during the “negative” (eccentric) action of the muscle.  The track athletes often strain the hamstring during the stride when the knee is brought forward followed by the forward swing of the foot.  The hamstring has a negative muscle action to slow down the lower leg so the knee is not hyperextended prior to the positive muscle action to pull the entire lower leg down.  The bodybuilders will strain the hamstring most often by overstretching the hamstring when performing stiff-legged deadlifts while standing on a bench.  If the weight is also too heavy the chance of injury is greater and even moreso if the muscle is fatigued or if the trainee’s overall system is fatigued.  Muscular injuries usually resolve, even if not well, if given enough time and rest.

However, sometimes the trainee can have pain down the hamstring from other causes.  Another source of this pain is often referred to as sciatic pain or sciatica.  This nerve travels between the hamstring muscles.   More specifically, spinal nerve roots can become inflamed at the site the nerves exit the spinal canal in the lower back.  The spine is made of bony segments known as vertebrae.  There is a shock absorber between each pair of vertebrae.  This shock absorber is known as a disc, or intervertebral disc.  Nerves exit the spine between each pair of vertebrae.  There is a semi-lunar-shaped space on the bottom and top of each vertebra and these spaces line up to make a tunnel-like space for the nerves to exit.  This space for the nerves to exit is known as the neural foramen.  As noted, the disc helps the spine absorb shock and it provides space between the vertebrae so there is enough room for the nerves to exit.  Sometimes the disc is injured in manner that is commonly referred to as disc protrusion or lay terms, a herniation.  At the time of the injury, there is often inflammation around the disc.  The nerve passes close to this area and can become inflamed too.  Once one of two lower nerves of the back, named and numbered L5 or S1, become inflamed, symptoms can begin to occur.  These nerves contribute to the sciatic nerve.  The symptoms can include pain, numbness and tingling from the low back down through the gluteal area and down the hamstring region and sometimes into the calf and foot. 

There are several types of disc injuries.  Some of these injuries produce back pain and some do not.  Additionally, narrowing of the space where the nerve exits (foraminal stenosis) can cause hamstring strain-like pain also.   The next installment will delve into this problem which can masquerade as a hamstring injury.