What is Piriformis syndrome?

Piriformis syndrome is an uncommon cause of sciatica. The piriformis is a muscle that lies deep underneath the gluteal muscles of the buttocks. The function of the piriformis muscle is to externally rotate and stabilise the hip. The sciatic nerve passes directly underneath the piriformis. Piriformis syndrome occurs when the piriformis muscle becomes tight, goes into spasm, or swells. When this happens it compresses the sciatic nerve beneath it. In roughly one in 7 people, the sciatic nerve passes through the piriformis instead of underneath it – and these people may be prone to sciatic nerve problems

A recent review of Piriformis syndrome concluded the cause of this condition may be multi-factorial.  In reviewing the literature it is apparent that two different syndromes involving the piriformis muscle have been identified. Some authors
describe “Piriformis Muscle Syndrome” as buttock pain due to spasm of piriformis muscle others refer to it as “Piriformis Impingement”. They title the second condition associated with chronic piriformis muscle shortening or spasm as “Piriformis Muscle Strain”.

How is it diagnosed?

Piriformis syndrome is primarily diagnosed by recognition of some or all of the following symptoms;

• Ache in the deep buttock region,
• Discomfort in sitting on the affected side,
• Pain down the back of the thigh, calf and sole of the foot,
• Tingling, pins and needles, down the leg,
• Burning sensation along the distribution of the sciatic nerve,
• Decreased and abnormal sensations,
• Numbness and muscle weakness on the affected side,
• Trouble walking, “feels weak when I put pressure on my right foot”,
• The pain typically can increase with prolonged sitting, walking up stairs, deep squats, or pressure directly over the muscle and when the muscle contracts.
• An aching sensation may be experienced with prolonged weakness if there is long term compression to the sciatic nerve.
Piriformis syndrome is diagnosed using a number of tests and palpation skills by your therapist.

Examination findings:

• Piriformis muscle spasm often is detected by careful deep palpation.
• Digital rectal examination may reveal tenderness on lateral pelvic wall that reproduces symptoms.
• Reproduction of sciatica type pain with weakness is noted by resisted abduction/external rotation (Pace test).
• The Freiberg test is another diagnostic sign that elicits pain upon forced internal rotation of the extended thigh.
• The Beatty manoeuvre reproduces buttock pain by selectively contracting the piriformis muscle. The patient lies on the uninvolved side and abducts the involved thigh upward; this activates the ipsilateral piriformis muscle, which is both a hip external rotator and abductor with the hip flexed.
• A painful point may be present at the lateral margin of the sacrum.
• Shortening of the involved lower extremity may be seen.
• The patient may have difficulty sitting due to an intolerance of weight bearing on the buttock.
• The patient may have the tendency to demonstrate a splayed foot on the involved side when in the supine position.
• A Morton foot may predispose the patient to developing piriformis syndrome. The prominent second metatarsal head destabilizes the foot during the push-off phase of the gait cycle, causing foot pronation and internal rotation of the lower limb. The piriformis muscle (external hip rotator) reactively contracts repetitively during each push-off phase of the gait cycle as a compensatory mechanism, leading to piriformis syndrome.

Therapists may require you to see a sports physician for further investigations to assist with the accurate diagnosis of piriformis syndrome.

Imaging Studies:

• Diagnostic imaging of the lumbar spine is mandatory to exclude associated discogenic and/or osteoarthritic contributing pathology.
• Reports in the literature on piriformis muscle describe imaging by nuclear diagnostic studies and MRI of the pelvis, but these tests are neither practical nor reliable diagnostic approaches to this problem. The history and clinical diagnostic examination provide the greatest and most specific diagnostic yield for this problem.
• Diagnostic ultrasound imaging of the piriformis muscle for assessment of muscle morphology has demonstrated a significant correlation of piriformis muscle morphology abnormality, especially in patients with lumbosacral/buttock pain and pain ascending stairs, referred pain to the posterior thigh on the symptomatic side, and reproduction of pain with needling of the piriformis muscle.

Other Tests:

• CT or MRI examinations of their buttocks have not been proven to show enough information to accurately diagnose this condition and are therefore not routinely administered.

What exercise program should I be doing?

Rehabilitation Program:

1. Physiotherapy:
Because it is difficult to accurately diagnose this problem, treatment regimens are controversial. Despite this fact, numerous treatment strategies exist for patients with piriformis syndrome.

Functional biomechanical deficits may include the following:

• Tight piriformis muscle
• Tight hip external rotators and adductors
• Hip abductor weakness
• Lower lumbar spine dysfunction
• Sacroiliac joint hypomobility

Functional adaptations to these deficits include the following:

• Ambulation with thigh in external rotation
• Functional limb length shortening
• Shortened stride length

Once the diagnosis has been made, these biomechanical factors must be corrected.

Consider the use of ultrasound and other heat modalities prior to physical therapy sessions. Soft tissue therapies of the piriformis muscle can be helpful. Addressing sacroiliac joint and low back dysfunction is also important.

A home stretching program should be provided to the patient. These stretches are an essential component of the treatment program. During the acute phase of treatment, stretching every 2-3 hours (while awake) is a key to the success of non-operative treatment.

Are there other alternatives?

Should this fail further treatment such as non-steroid anti-inflammatory drugs and injection of local anaesthetics and corticosteroids may be appropriate.  In resistant or severe cases operative techniques should be employed.

References

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