The hamstring is a very important muscle, but if can be a deceiving one as well. It is made up of three muscles that all originate at the ischial tuberosity (sit bone) on the pelvis. They then insert to various areas of the tibia/fibula distal to the knee, resulting in a primary motion of knee flexion (bring the heel to the buttock). Many musculoskeletal practitioners link the tightness in this muscle to lumbo-sacro-pelvic dysfunction with the belief that as the muscle shortens it will pull on the posterior aspect of the pelvis, resulting in a posteriorly rotated innominate and the resulting associated dysfunctions. While this can be true in a more acute setting, in the chronic setting of low back pain the hamstring is actually one of the only things preventing higher levels of mechanical pain. While we like to separate our anatomy into sections to make explanations and understanding easier, everything really is connected. So, if you follow the hamstring tendon superiorly as it crosses the ischial tuberosity it will turn directly into the sacrotuberous ligament. The sacrotuberous ligament, named for it’s attachments to the sacrum (tailbone) is the most important and primary ligamentous stabilizer for the low back. When there is dysfunction or instability in the sacral area, it will result in tension in the sacrotuberous ligament to prevent a bigger problem. This was well studied and reported by Andry Vleeming. As the sacrotuberous ligament becomes taught, it will of course pull on the surrounding/attached structures. This is what results in the chronic tighting of the hamstring muscles. Depending on the severity and location of the mechanical issue in the back, it could be one side or both sides. This is a very important concept to understand when approaching patients with low back pain. I see time and again practitioners that put a lot of emphasis on stretching and releasing the hamstring, which effectively undoes the hard work the body is doing to help keep things stable and control the pain. In some circumstances I have found that a foam roller to the hamstring can loosen this muscle, without loosing the sacrotuberous ligament. As a rule though, the hamstring should be the last thing that is treated. Once the mechanical issues in the low back have improved, the tension will be removed from the sacrotuberous ligament and the hamstring tightness will resolve itself.
Movement, Stability and Low Back Pain by Andry Vleeming