The piriformis (say: pir-uh-FOR-mis) muscle runs from the sacrum in the lower part of the spine, across the sacro-iliac joint to the top of the thigh bone, or femur. The sciatic nerve runs directly under this muscle. When the muscle becomes tight or spasms, it may cause a brief irritation of the nerve. This condition can be fairly acute, as in runners who get symptoms when they overtrain, or chronic. It appears to affect women more often than men (ratio of 6:1).
Signs and symptoms
- aching buttock pain
- pain going down the back of the leg (but not beyond the knee)
- pain is sometimes described as burning, tingling, or electric shocks, most often when the sciatic nerve is irritated
- pain may be worse when sitting for a long time, stooping or lifting, climbing , or running
pain with sex or rectal pain
Falls (direct impact to the buttocks) or motor vehicle crashes can set this process in motion by injuring the ligaments of the sacro-iliac joints. Leg lengths that are not equal and poor hip muscle strength can also add to the muscle becoming tight and causing tender points.
This disorder can most often be diagnosed based solely on the symptoms and the physical exam. In some cases, an magnetic resonance imaging (MRI), nerve conduction study, or other tests may need to be done to rule out other problems like a stress fracture or an irritation of the nerve root, close to the spine.
Stretching, TENS, or acupuncture
At first, the treatment approach consists of stretching exercises for the piriformis muscle. This is often done under the guidance of a physiotherapist. Some people find massage, transcutaneous electrical nerve stimulation (TENS), or acupuncture helpful as well. Sometimes, your physiotherapist or kinesiologist will suggest that you stop the things you are doing that flare up the pain for the time being. Some other healthy activity should be done instead.
Seat cushion, sacro-iliac belt, heel lift
Other things that your doctor may suggest include:
Medicines and injections
Over-the-counter medicines such as acetaminophen (Tylenol) or ibuprofen can be useful to manage pain during rehab. The doctor may recommend an injection of local anaesthetic into the muscle itself (trigger point injection). This is also a short term effect designed to allow more consistent stretching exercise. Sometimes, Botox (botulinum toxin type A) injections can be useful for people with a lot of pain despite a good rehab program. In very rare cases, the doctor may suggest surgery, if there is a very specific problem in the piriformis muscle.
For more information
American Pain Foundation
TRIP Database (Resources for Evidence Based Medicine)
University of Michigan Health System (piriformis syndrome rehabilitation exercises)
Adkins SB and Figler RA. Hip pain in athletes. American Family Physician. 2000;61(7):2109-18.
National Institute of Neurological Disorders and Stroke, National Institutes of Health NINDS. Piriformis syndrome information page., Bethesda, MD. Last updated February 14, 2007.