Piriformis syndrome: what is it? How do you get it? How do you know you have it? How do you get rid of it? What else do you need to know? That's the substance of this review article written by two well-known and well-respected physiotherapists on the subject of piriformis syndrome.
Let's start with: what is the piriformis syndrome? Piriformis syndrome is an irriation of the sciatic nerve as it passes next to or through the piriformis muscle. The piriformis muscle is a flat, pyramid-shape structure. It starts along the anterior (front) part of the sacrum and inserts or attaches on the greater trochanter of the femur. That's a bony bump at the top of the upper thigh bone.
The muscle is close enough to the sciatic nerve that the muscle can put pressure on the nerve when it contracts or if it gets bulky enough from repetitive overuse. In about 10 per cent of all cases, the sciatic nerve actually runs through the piriformis muscle. Anytime the muscle contracts, the nerve gets squeezed.
Some experts think it's this pressure that causes the symptoms that make up piriformis syndrome. Those symptoms include aching, burning, or sharp pain in the area controlled by the sciatic nerve. The pain starts in the mid-buttocks on one side and can shoot down the upper leg. Symptoms may go down as far as the knee but only occasionally go past the knee. How far down the leg the pain goes can help distinguish it from a herniated disc. Pain that does go past the knee down to the foot is more likely to be from a protruding disc putting pressure on the spinal nerve root.
Before going much further, it's important to say there are some medical specialists who don't believe the piriformis syndrome even exists. So, some effort has been put into identifying just what constitutes the idea of a piriformis syndrome. Here are six indicators of this condition:
- History of trauma to the buttock or sacroiliac area
- Pain in the sacroiliac joint or area of the piriformis muscle
- Pain that's made worse by stooping or lifting and relieved with spinal traction
- A soft nodule that is easily felt in the area of the SAI joint
- A positive straight leg raise test
- Atrophy or wasting of the buttock (gluteal) muscle
Besides trauma, what else can cause this problem? Repetitive overuse of the muscle, myofascial trigger points, anatomic variations, postural factors, and a difference in leg length. The risk of developing piriformis syndrome increases any time someone stands on one leg more than the other, sits on one foot, sits crossed-leg, or stands habitually with the hip turned out (external rotation. Walking with the leg too close to the other leg and with internal rotation of the leg can also increase the strain on this muscle resulting in piriformis syndrome.
How can you know for sure that you have this thing called piriformis syndrome? It's not always easy. There are many other possible causes of sciatica and there isn't one test that separates piriformis syndrome from other problems. Sciatica is also caused by tumors, lumbosacral strain, lumbar disc herniation, and spinal stenosis (narrowing of the spinal canal around the spinal cord).
Most often, the examiner must ask lots of questions about history and symptoms, perform some specific clinical tests, and sometimes order special tests such as a CT scan or MRI. They say the diagnosis is really one by exclusion. That means when all other conditions have been ruled out, piriformis can be ruled in. Some of the more common tests performed include reflexes, straight-leg raise, the Pace test, Freiberg test, flexion adduction and internal rotation (FAIR) test, and the Beaty test.
The authors describe each test and offer what they could find in the literature to say which tests are the most valid, reliable, sensitive, and specific. Most of these tests place the patient's leg in different positions to stretch the piriformis muscle and see if the painful symptoms are reproduced. Studies show that the FAIR test has the best chance of ruling in piriformis syndrome. The test procedure of stretching the muscle is also the most commonly prescribed treatment program.
Stretching to lengthen the muscle is believed to be the best way to decrease the compression put on the sciatic nerve when the piriformis contracts. Sometimes a form of deep heat called ultrasound is used by physiotherapists before starting the stretching exercises. This has been shown to alter the connective tissue bonds enough to allow them to break so that the muscle fibers lengthen during the stretching procedure.
It's important to check the patient for any other biomechanical reasons for piriformis syndrome. For example, having a leg-length difference (one leg longer than the other) can be a contributing factor. The examiner will review your risk factors. A previous history of cancer (especially cancers that spreads to the bone) is important. The presence of any suspicious lumps or palpable nodules requires further investigation. Usually an X-ray and a few lab tests are all that are needed to rule out some underlying systemic (disease) cause of the problem.
Knowing the specific signs and symptoms for each of the other conditions that can cause sciatica can help the examiner sort out what is and what is not piriformis condition. Sometimes it isn't until the therapist tries a treatment approach that it becomes clear what is the problem. When physiotherapy doesn't help, a series of BOTOX injections might be advised. This treatment technique has been supported by recent scientific studies. Physiotherapy combined with injections has been shown to be the most effective so far.
In summary, the authors looked for evidence of the highest level to help form clinical judgment, diagnostic strategies, and effective treatment options for piriformis syndrome. The goal is to help therapists get on the same page and treat piriformis syndrome in the same way across the country no matter where a patient lives. Most of the evidence available to date is moderately low in quality. More studies on this topic are needed to identify the best diagnostic test or tests and then the best evidence-based way to treat the problem.
Arthur Hulbert, PT, DPT, and Gail D. Deyle PT, PhD. Differential Diagnosis and Conservative Treatment for Piriformis Syndrome: A Review of the Literature. In Current Orthopaedic Practice. May/June 2009. Vol. 20. No. 3. Pp. 313-319.