Piriformis syndrome: the causes, diagnosis and treatment of this common gluteal muscle injury
Alicia Filley, PT, MS, PCS, lives in Houston, Texas and is vice president of Eubiotics: The Science of Healthy Living, which provides counselling for those seeking to improve their health, fitness or athletic performance through exercise and nutrition.
Piriformis syndrome is an irritation of the sciatic nerve caused by an inflammation of the piriformis muscle
If you experience pain in the buttocks that radiates along the rear thigh, you may be suffering from piriformis syndrome. Alicia Filley explains the causes of this condition and what can be done to relieve the pain in your bum…
The piriformis is a muscle that lies deep within the buttocks, covered by the gluteal muscles. It originates on the front surface of the sacrum, passes through the greater sciatic foramen, and inserts into the greater trochanter of the femur (see figure 1). It functions to externally rotate the hip when it is extended and abduct the hip when it is flexed.
The sciatic nerve is the largest nerve in the body and originates from the spinal cord at the level of the fourth lumbar vertebrae through the third sacral vertebrae. This nerve lies in close proximity to the piriformis muscle and in the majority of the population, the nerve emerges from the pelvis just below the piriformis muscle. However, surgical observation and cadaver studies reveal that variations in the relationship between the two occur in as much as 22% of the population (see figure 1)(1).Piriformis syndrome is an irritation of the sciatic nerve caused by an inflammation of the piriformis muscle. Athletes may complain of a deep aching pain in the buttock or a radiating sharp nerve pain that extends along the middle of the rear thigh. Occasionally, numbness and tingling can continue to the calf and toes. These symptoms can be accompanied by low back pain and worsen after prolonged sitting. Because the symptoms of piriformis syndrome mimic those of a herniated disc pressing upon the sciatic nerve, a thorough exam by a physician should be conducted to rule out more serious origins.
Conversely, a diagnosis of disc disease, common in older runners and cyclists, does not exclude piriformis syndrome from being the cause of pain. Researchers in California evaluated 239 patients who suffered from sciatic pain of non-disc origin(2). Many of them previously underwent lumbar spine surgery because the origin of the pain was thought to be disc herniation. In this group of patients, the surgery provided little or no relief. Forty-two percent of those ultimately diagnosed with piriformis syndrome complained of low back pain. Because it is often a diagnosis of exclusion, it is difficult to pinpoint the actual incidence of piriformis syndrome in the population.
Testing for Piriformis Syndrome
Unfortunately, there is no definitive test to diagnose piriformis syndrome. One way to discern the origin of the sciatic pain is to reproduce it. A positive straight leg raise test (SLR) usually suggests a cause originating in the spine or sacrum rather than piriformis syndrome. With the athlete lying on his back, legs extended, an examiner lifts the leg on the side of the pain. If the sciatic pain is reproduced, the SLR is positive. Keep in mind, however, that in the California study, 41% of those diagnosed with piriformis syndrome exhibited a positive straight leg raise test upon initial examination.
If the pain is reproduced in the FAIR (hip flexion, adduction, internal rotation) position, then it is more likely due to piriformis syndrome. In the FAIR test, the athlete lies on the non-painful side and places the painful leg in a position of 60° hip flexion, knee flexion, hip adduction, and internal rotation(1). The examiner applies pressure to the knee in a downward direction thus placing the piriformis on a stretch that compresses the sciatic nerve (see figure 2).
Piriformis Syndrome Testing
Upon examination, there may be point tenderness over the piriformis muscle, which may be felt as a sausage-shaped mass. Postural changes may include sacral rotation toward the painful side, misalignment of the sacroiliac joint, and rotation of the lumbar vertebrae. With the athlete lying on his back, the painful leg may rest in external rotation due to a shortened piriformis muscle. Nerve conduction velocities below the level of the piriformis may be delayed, especially with the subject in the FAIR position.
In the early stages, piriformis syndrome begins as an inflammatory response to overuse, trauma, or postural misalignment. If the inflammation of the piriformis is severe, impingement of the sciatic nerve results. Treating the pain with over-the-counter non-steroidal, anti-inflammatory medications can reduce the pain and decrease inflammation. Other conservative treatments are recommended, such as rest, compression, and ice to the area.
As the syndrome progresses, a cycle of muscle spasm, pain and postural compensations can ensue. Treatment at this stage usually requires referral to a physiotherapist. Treatment modalities used to manage inflammation and decrease muscle spasm include ultrasound and cold spray. Manual therapies address soft tissue problems such as myofascial tightening and trigger points. Exercises and stretching then follow to lengthen the shortened muscle, strengthen the pelvic girdle, and correct postural imbalances. A 10-year study by researchers in New York found that physical therapy two to three times per week, for up to three months, yielded a 60%-70% improvement in symptoms for most patients (3).
While athletes are usually symptomatic in only one leg, the pain-free leg should be treated as well. In the New York study, investigators determined the most common causes of piriformis syndrome are overuse (43% of 876 patients) and trauma (18% of 892 patients). When nerve conduction studies were performed on the symptom-free leg of patients with piriformis syndrome in that same study, the results showed the values obtained in the symptom-free leg were significantly impaired when compared to non-injured controls. Overuse and trauma are usually experienced in both legs; both legs should therefore be included in any treatment program.
If conservative measures don’t provide relief, patients can be treated with an injection to the piriformis. When the researchers in the Californian study above suspected a patient had piriformis syndrome, the piriformis muscle was injected with anaesthetic and corticosteroid medication(2). Those patients who experienced complete, or near complete resolution of symptoms were confirmed to have piriformis syndrome. Patients whose symptoms returned in less than one week were referred for piriformis surgery. Those whose symptoms returned after one week were treated with up to two additional injections at four-week intervals. If the subsequent injections did not provide complete relief, these patients were also referred for piriformis surgery.
Of the 239 patients evaluated, 68% were diagnosed with piriformis syndrome. Of those, 23% experienced complete relief after one or two injections. Thirty-seven percent experienced prolonged relief from the injections (more than six months) followed by a recurrence of symptoms. However, the treatment with injections was not accompanied by follow-up physiotherapy, and this may explain why the symptoms returned.
If surgery is required, the piriformis muscle tendon is released, thus easing the tension that compresses the sciatic nerve. The sciatic nerve is also examined for scarring or connective tissue adhesions that may cause irritation. Of those who were referred for surgery in the California study, 59% rated their initial surgical outcome as excellent. Those who participated in long-term follow up (greater than two years after surgery) reported excellent results in 62% of the cases.
What was once a major surgery (with an incision similar to that of a hip replacement) is now conducted via an incision roughly three centimetres in length. Consequently, piriformis surgery is no longer a competition-ending procedure. Most return to daily activities within two weeks and athletes can return to training activities such as deep water running or swimming fairly quickly.
Small Muscle, Big Problem
Functionally, releasing the piriformis has a small impact on hip biomechanics because the piriformis is a fairly weak external rotator and abductor. So how does this pip-squeak of a muscle become such a pain in the bum? Both internal and external factors influence the progression of piriformis syndrome. Internal factors include the anatomical configuration of the piriformis in relation to the sciatic nerve, postural misalignments such as a leg length discrepancy, infection in the muscle, myositis ossificans, and tumor(4).
In runners, overuse occurs due to external factors such as excessive mileage, advancing mileage too quickly, or poor running technique. Changing terrain, wearing worn shoes, or running on banked surfaces can also over-tax weak muscles. As the primary muscles of the hip become fatigued, the smaller accessory muscles, such as the piriformis, must work harder to maintain form. Trying to compensate for stronger muscles is how the piriformis becomes strained. A traumatic fall or blow to the buttocks can injure the piriformis and trigger the inflammatory response as well.
A good rule of thumb for increasing mileage is no more than 10% per week. It is important to remember to vary the direction of running on a track or banked road. The functional leg length discrepancy that results when running on a tilt, places an added strain on the pelvic musculature. An actual leg length discrepancy of a centimetre or more affects pelvic alignment. A physiotherapist can evaluate the need for a shoe lift in such cases. Core strengthening of the pelvic girdle musculature is the best way to ensure that the muscles are prepared to handle any external factors you may encounter.
Stretching and Strengthening
The need to stay strong
Endurance athletes, especially runners, are notorious for ignoring the strengthening portion of their training programme. Many assume that merely performing their sport will produce adequate strength but in running, the opposite is true. Endurance runners performing longer running workouts actually lose muscle strength in their legs. Fitness experts in New York evaluated hip strength in eight men and eight women before and after a 2-hour run(5). Hip abduction strength decreased by 17% in men and 12% in women; adduction strength decreased by 18% and 17% respectively; and hip flexion strength decreased by 19% in both.
Meanwhile, researchers from Minnesota conducted a descriptive analysis of hip strength in runners with a running injury(6). A significant relationship was found between hip weakness and running injury in 30 recreational runners. The musculature of the injured leg was significantly weaker than that of the non-injured leg. Moreover, a matched control group of injury-free runners did not exhibit the disparity in hip strength between legs that the experimental group did. While not proving a causal relationship, it highlights the role that hip strength plays in the prevention of injury.
Improving hip strength may also improve performance. Scientists in Spain and the US jointly examined the effects of a sport-specific, periodised, strength-training programme on the loss of stride length in endurance runners(7). Eighteen sub-elite runners were randomly assigned to one of three training scenarios. For eight weeks during the training cycle, the subjects either performed a periodised strength-training programme, a non-periodised strength-training programme, or no additional strength training.
The stride length to speed (SLS) ratio was then measured during training intervals at race speeds for up to 20 repetitions of the racecourse. Comparing the SLS from the first and last third of the repetitions, researchers found that those who participated in a running specific, periodised, strength-training programme did not show any decrease in the SLS between the first races and the last. On the other hand, the runners in the other two categories both showed significant decreases in the SLS, with that of the non-strength training group being the greatest (see figure 3 (7)).
Clearly, the longer you can hold off muscle fatigue, the more consistent your stride length, and therefore, the better your performance. Training the appropriate muscles to do their job through specific strength training prevents accessory muscles from having to stand in for them. This brings better results on the racecourse and keeps athletes injury free.
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2. J Neurosurg Spine. 2005 Feb;2:99-115.
3. Arch Phys Med Rehabil. 2002 Mar;83(3):295-301.
4. Orthop Clin N Am. 2004;35:65-71.
5. J Orthop Sports Phys Ther. 1998 March;27(3):189-196.
6. Clin J Sport Med. 2005 Jan;15(1):14-21.
7. J Strength Cond Res. 2008;22(4):1176-1183.