The piriformis muscle is located in the gluteal/buttock region at the back of the pelvis. Anatomically, this muscle originates from the front of the sacrum and inserts onto the hip. Its main actions are to rotate the hip outwards (laterally) when the hip is bent to less than ninety degrees and to rotate the hip inwards when the hip is bent greater than ninety degrees. This muscle also functions to stabilise the hip in its ball-and-socket joint.
The sciatic nerve is the largest nerve is the body. It begins in the low back and then travels through the buttock and into the lower limb. In 15-20% of the population, the sciatic nerve pierces the belly of the muscle of the piriformis, giving rise to sciatica. In addition, contracture or spasm of this muscle can lead to chemical or mechanical irritation of the sciatic nerve, giving rise to signs and symptoms such as pins and needles, radicular pain, muscle weakness and altered reflexes.
In the absence of imaging, it can be difficult to distinguish between nerve root irritation/sciatica arising from a disc injury or Pirifomis syndrome. Resisted external rotation of the hip, passive internal rotation or performing a straight leg raise (SLR) with a degree of inward rotation of the hip may all reproduce pain with piriformis syndrome, however, these findings are not conclusive.
(The list of conditions given above and subsequent explanations are intended as a general guide and should not be considered a replacement for a full medical examination. Furthermore, we do not purport to treat all the conditions listed. Should you wish to discuss any of these conditions with our chiropractors, please do not hesitate to phone the clinic on 020 7374 2272 or email firstname.lastname@example.org).