Piriformis syndrome (PS) is a condition that is characterized by a combination of symptoms that include low back or buttock pain that refers down the leg. Piriformis syndrome is caused by a tight, inflamed and tender piriformis that can result in compression of the sciatic nerve due to its proximity to, or in some cases coursing through the muscle.1
The piriformis is a flat muscle that originates from the anterior aspect of the sacrum, the upper aspect of the greater sciatic notch and the sacrotuberous ligament.2 The pirifromis runs inferiolateraly through the greater sciatic foramen to the superior aspect of the greater trochanter. The piriformis is innervated by the nerve to the piriformis which is supplied by the ventral rami of S1 and S2.1 When the hip is extended the piriformis externally rotates the hip, weakly abducts the hip, weakly flexes the hip, and stabilizes the femoral head during ambulation.2 When the hip is flexed the piriformis acts primarily as a hip abductor.1 The piriformis has a close relationship with the sciatic nerve. The sciatic nerve is made up of the ventral rami of L4 to S3 which come together just inferior to the piriformis in the greater sciatic foramen.1 In as much as 22% of the population the sciatic nerve runs through the piriformis, splits and runs superiorly and inferiorly to the piriformis, or both. People who have one of these abnormalities are predisposed to having PS.2
The piriformis has been thought of as a possible cause of sciatica for years. Sciatica was first attributed to the inflammation of the SI joint and pirformis in 1928 by Yeoman. The idea rose from both the SI joint and piriformis muscle having an anatomical proximity to the sciatic nerve as it exits the greater sciatic foramen. The term piriformis syndrome was first used by Robinson in 1947. His description of PS included 6 key features: trauma or fall directly on the buttock, gluteal or SI pain that radiates down the leg and possibly limits ambulation, a palpable mass in the muscle, atrophy of the gluteal muscles, positive lasegue sign, and worsening of symptoms when bending or lifting.1
The incidence piriformis syndrome is hard to pinpoint because there is no operational definition of the disorder. Attempts to establish an operational definition of the disorder have been made, but none are definitive.3
Signs and Symptoms: as stated by Boyajian-O'Neill L et al
▫ Pain with sitting, standing, or lying longer than 15 to 20 minutes
▫ Pain and/or paresthesia radiating from sacrum through gluteal area and down posterior aspect of thigh, usually stopping above knee Pain improves with ambulation and worsens with no movement
▫ Pain when rising from seated or squatting position
▫ Change of position does not relieve pain completely
▫ Contralateral sacroiliac pain
▫ Difficulty walking (eg, antalgic gait, foot drop)
▫ Numbness in foot
▫ Weakness in ipsilateral lower extremity
▫ Neck pain
▫ Abdominal, pelvic, and inguinal pain
▫ Dyspareunia in women
▫ Pain with bowel movements
▫ Tenderness in region of sacroiliac joint, greater sciatic notch, and piriformis muscle
▫ Tenderness over piriformis muscle
▫ Palpable mass in ipsilateral buttock
▫ Traction of affected limb provides moderate relief of pain
▫ Asymmetrical weakness in affected limb
▫ Piriformis sign positive
▫ Lasègue sign positive
▫ Freiberg sign positive
▫ Pace sign (flexion, adduction, and internal rotation test result) positive
▫ Beatty test result positive
▫ Limited medial rotation of ipsilateral lower extremity
▫ Ipsilateral short leg
▫ Gluteal atrophy (chronic cases only)
▫ Persistent sacral rotation toward contralateral side with compensatory lumbar rotation
The patient may present with pain in the buttock, with the pain possibly radiating down the posterior thigh to the knee if the posterior cutaneous nerve of the thigh is agitated. This pain usually worsens with prolonged sitting or when moving from sit to stand. The patient will likely be externally rotated and appear to be holding their leg in a shortened position.4
Pain is elicited by positions that promote internal rotation such as the FAIR (flexion, adduction, internal rotation) position. This pain is a result of activating the muscle to promote external hip pain. During the physical examination the patient will display tenderness upon palpation of the piriformis or the greater trochanter. Diagnostic tests are used to aid in diagnosing PS.1
The term piriformis syndrome is used in order to describe a series of symptoms that are caused by the irritation or compression of the sciatic nerve. There is no agreed upon etiology that causes piriformis syndrome, however a number possibilities have been proposed. A popular explanation is that the piriformis muscle becomes inflamed as a result of a trauma which in turn compresses the sciatic nerve.5 Fishman et al found that the most common cause of piriformis syndrome was overuse.6 Postural influences have also been taken into consideration, such as, frequent single leg stance, sitting on one foot, or extended periods of hip external rotation. Leg length discrepancy has also shown a correlation with piriformis syndrome. Antalgic gait where the affected hip is held in a position of adduction and internal rotation can also place strain on the piriformis.5
Diagnosis of PS is mostly differential and one of exclusion. In order to ascertain a diagnosis of PS the clinician must rule out herniated nucleus propulpsus, facet arthropathy, spinal stenosis, and lumbar muscle strain.1 Diagnostic machines such as CT, MRI, ultrasound and EMG are beneficial for ruling out other possible conditions. MRI machines can be useful for assessing the piriformis muscle itself both for abnormalities in respect to the sciatic nerve and the muscle itself.1
Evaluation/Special orthopedic tests:
The Freiberg maneuver consists of forcefully internally rotating the leg in order to stretch the aggravated piriformis.12
During the Pace maneuver the patient has his leg abducted while seated which irritates the piriformis and causes pain if positive.1
The Beatty maneuver is positive when pain is reproduced in the buttock, not the lumbar spine, when the patient actively abducts the leg in side lying position.1
The FAIR maneuver reproduces buttock pain when the hip is passively flexed, adducted, and internally rotated.1
Physical therapy is an effective treatment for piriformis syndrome. Common treatment techniques include stretching exercises, manipulation, myofascial release, McKenzie principle exercises, ultrasound, hot packs and ice. Stretching is the most frequently used intervention for the treatment of piriformis syndrome. Stretching the piriformis is used to loosen the muscle which results in decreased pressure on the sciatic nerve. Ultrasound is also commonly used over the piriformis to provide a mechanical and deep heat to reduce pain and to facilitate stretching.5
When treating for piriformis syndrome it is important to take into consideration biomechanical anomalies. The most common anomaly is leg length difference. In order to compensate for this abnormality the patient should use a leg lift to make up for the difference.5
Recent literature suggests the use of botox in combination with physical therapy. Botox inhibits the release of ACH before the synapse, which leads to the affected muscle being paralyzed. The weakness, atrophy and relief of the sciatic nerve compression are all result of the botox, which essentially reverses the underlying pathophysiology of PS.1 In a 10 year cohort study it was reported reported that patients who received the botox injection had immediate pain relief, however without physical therapy the pain returned in a few weeks. When the injections were combined with physical therapy 81% of patients who tested positive for piriformis syndrome initially had their symptoms improved by 50% or more.6
The most common procedure is the surgical release of the piriformis and decompression of the sciatic nerve. The procedure is straight forward when 3 guidelines for patient selection are followed. The first criteria is that a thorough clinical assessment has been performed and substantiates the diagnosis of piriformis syndrome. The second is that the patient’s motivation and interest in recovering. The third factor is that the patient has reasonable expectations for the outcomes of the procedure.7
The procedure consists of the piriformis being dissected back to the sciatic notch and then the relationship of the sciatic nerve and the piriformis being examined. After this has been completed 1.5 to 2 cm of the distal piriformis stump is resected. If all has gone well this is followed by a routine closure of the incision.7
After surgery the patient is weight bearing as tolerated, but it is common for them to use crutches for 1 to 2 weeks in order to normalize gait. The patient is also advised to avoid prolonged sitting, and to be cautious for the first 4 to 6 weeks post-surgery. Symptomatic improvement can be expected within the first 6 weeks, however incisional discomfort can last a few months.7
1. Kirschner JS, Foye PM, Cole JL. Piriformis syndrome, diagnosis and treatment. Muscle Nerve. 2009;40(1):10-18. http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=19466717&site=ehost-live.
2. Boyajian-O'Neill L, McClain RL, Coleman MK, Thomas PP. Diagnosis and management of piriformis syndrome: An osteopathic approach. JAOA J AM OSTEOPATH ASSOC. 2008;108(11):657-664. http://search.ebscohost.com/login.aspx?direct=true&db=cin20&AN=2010121334&site=ehost-live.
3. Hopayian K, Song F, Riera R, Sambandan S. The clinical features of the piriformis syndrome: A systematic review. Eur Spine J. 2010;19(12):2095-2109. http://search.ebscohost.com/login.aspx?direct=true&db=jlh&AN=2010877483&site=ehost-live. doi: 10.1007/s00586-010-1504-9.
4. Windisch G, Braun EM, Anderhuber F. Piriformis muscle: Clinical anatomy and consideration of the piriformis syndrome. Surg Radiol Anat. 2007;29(1):37-45. http://search.ebscohost.com/login.aspx?direct=true&db=cmedm&AN=17216293&site=ehost-live.
5. Hulbert A, Deyle GD. Differential diagnosis and conservative treatment for piriformis syndrome: A review of the literature. CURR ORTHOP PRACT. 2009;20(3):313-319. http://search.ebscohost.com/login.aspx?direct=true&db=cin20&AN=2010302779&site=ehost-live.
6. Fishman LM, Dombi GW, Michaelsen C, et al. Piriformis syndrome: Diagnosis, treatment, and outcome — a 10-year study. Arch Phys Med Rehabil. 2002;83(3):295-301. http://search.ebscohost.com/login.aspx?direct=true&db=cin20&AN=2002077240&site=ehost-live.
7. Byrd JWT. Piriformis syndrome. Operative Techniques in Sports Medicine. 2005;13(1):71-79. http://articles.sirc.ca/search.cfm?id=S-1001973; http://search.ebscohost.com/login.aspx?direct=true&db=sph&AN=SPHS-1001973&site=ehost-live; http://articles.sirc.ca/search.cfm?id=S-1001973.