Piriformis syndrome can be another cause of work-related sciatica.  Pain in the buttock that radiates down the leg is called sciatica.  Sciatica is due to irritation of the spinal nerves in or near the lumbar spine.  In most of our workers compensation cases, sciatica is caused by a bulging or herniated intervertebral disc.  The jelly-like center of the disc, the nucleus pulposus, oozes out and touches the descending nerve roots as they leave the spinal cord, causing pain down the leg.  Another cause of sciatica can be sacroiliac or SI joint dysfunction.  A third cause of work-related sciatica can be piriformis syndrome.

The lower lumbar spinal nerves leave the spine and join to form the sciatic nerve. The sciatic nerve leaves the pelvis through an opening called the sciatic notch.  The piriformis muscle begins inside the pelvis. It connects to the sacrum, the triangular shaped bone that sits between the pelvic bones at the base of the spine. The connection of the sacrum to the pelvis bones forms the sacroiliac joint. There is one sacroiliac joint on the left and one on the right of the low back. The other end of the piriformis muscle connects by a tendon to the greater trochanter, the bump of bone on the top side of the hip.

The piriformis muscle is one of the external rotators of the hip and leg. This means that as the muscle works, it helps to turn the foot and leg outward. Problems in the piriformis muscle can cause problems with the sciatic nerve. This is because the sciatic nerve runs under (and sometimes through) the piriformis muscle on its way out of the pelvis. The piriformis muscle can squeeze and irritate the sciatic nerve in this area, leading to the symptoms of sciatica.

In some cases, the piriformis muscle may be injured when the worker falls on his buttocks.  Many doctors think that the condition begins when the piriformis muscle goes into spasm and tightens against the sciatic nerve, squeezing and irritating the nerve against the bone of the pelvis.  

The sciatic nerve stays irritated and continues to be a problem.  This is especially true if the worker has job duties that involve repetitive bending, lifting and turning while using muscles such as the piriformis.  Eventually the muscle heals, but some of the muscle fibers inside the piriformis muscle are replaced by scar tissue. Scar tissue is not nearly as flexible and elastic as normal muscle tissue. The piriformis muscle can tighten up and put constant pressure against the sciatic nerve.

At McCormick Law Office our attorneys have experience with work-related piriformis syndrome workers compensation claims.  Next blog will address symptoms and treatment of piriformis syndrome.