Piriformis syndrome is a condition in which the piriformis muscle, located in the buttock region, spasms and causes buttock pain. The piriformis muscle can also irritate the nearby sciatic nerve and cause pain, numbness and tingling along the back of the leg and into the foot (similar to sciatic pain).
The Piriformis Muscle
The piriformis muscle is a small muscle located deep in the buttock (behind the gluteus maximus).
The piriformis muscle:
- Starts at the lower spine and connects to the upper surface of each femur (thighbone)
- Functions to assist in rotating the hip and turning the leg and foot outward
- Runs diagonally, with the sciatic nerve running vertically directly beneath it (although in some people the nerve can run through the muscle).
Causes of Piriformis Syndrome
The exact causes of piriformis syndrome are unknown. Suspected causes include:
- Muscle spasm in the piriformis muscle, either because of irritation in the piriformis muscle itself, or irritation of a nearby structure such as the sacroiliac joint or hip
- Tightening of the muscle, in response to injury or spasm
- Swelling of the piriformis muscle, due to injury or spasm
- Bleeding in the area of the piriformis muscle.
Any one or combination of the above problems can affect the piriformis muscle (causing buttock pain) and may affect the adjacent sciatic nerve (causing pain, tingling, or numbness in the back of the thigh, calf, or foot).