Piriformis syndrome (pseudo-sciatica)

The piriformis arises from the anterior surface of the sacrum (S2–S4), the margin of the greater sciatic foramen and the sacrotuberous ligament, and inserts on the superior border of the greater trochanter. It is supplied by the nerve to piriformis (S1–S2, often with L5). It laterally rotates the extended hip and abducts the flexed hip; past roughly 60–90° of flexion its rotational action reverses towards internal rotation.

Passing through the greater sciatic foramen, it divides it into supra- and infrapiriform foramina. The sciatic nerve normally leaves through the infrapiriform foramen, deep to the muscle, then runs through the deep gluteal space between the ischial tuberosity and the greater trochanter. A hypertrophied, shortened or inflamed piriformis can compress or tether the nerve here, producing buttock pain with radiation along the sciatic distribution StatPearls, 2023.

Anatomical variants matter. In cadaver studies about 1 in 6 people (16.9%) have a variant course of the sciatic nerve relative to piriformis Smoll, 2010. The commonest (Beaton and Anson type B) sends the common fibular division through the muscle belly and the tibial division below it, which explains predominantly lateral-leg or dorsum-of-foot symptoms in some patients.

Primary piriformis syndrome comes from an intrinsic cause: anatomical variants of the muscle or nerve, or a split piriformis. Secondary piriformis syndrome, the large majority, follows macrotrauma, microtrauma and overuse, local ischaemia or a mass effect in the pelvis StatPearls. Many presentations sit under the wider heading of deep gluteal syndrome, of which piriformis is the best known cause Hernando et al., 2015.

1. Deep, often unilateral buttock pain, aching or burning, over the line from sacrum to greater trochanter
2. Radiation down the posterior thigh, sometimes to calf and foot, usually not in a clean dermatomal pattern
3. Paraesthesia or numbness in the sciatic distribution
4. Worse with sustained sitting (often unable to sit more than 15–20 min), stairs, squatting and running; eased by walking or standing

Low back pain is typically absent or minor. Dyspareunia is reported in some women. The history often contains a trigger: a new desk job, a long drive or flight, a jump in running volume, or a fall.

There is no single confirmatory test; the diagnosis rests on a consistent history, provocative tests that reproduce the patient's pain at the piriformis, and exclusion of spinal and other hip causes Chang et al., 2023.

Provocative tests

The Martin et al. figures come from 33 patients at a tertiary hip centre with endoscopy as the reference, so they likely overestimate accuracy in general practice. Use the cluster to raise or lower suspicion, not to confirm.

Neurological screen

Myotomes, dermatomes and reflexes are usually normal. A straight leg raise is rarely positive in gluteal entrapment (sensitivity 0.15 in the same study) and does not separate piriformis from disc pathology. A clear dermatomal deficit, reflex change or progressive weakness points to radiculopathy and needs onward assessment.

Investigations

Not needed for a typical presentation that responds to conservative care. When the picture is unclear or not settling: MRI of the lumbar spine to exclude a disc or stenosis; MR neurography may show sciatic nerve signal change or piriformis asymmetry; electrodiagnostics may show H-reflex prolongation in the FAIR position Fishman et al., 2002; an image-guided local anaesthetic injection into the piriformis can be diagnostic as well as therapeutic.

Conservative care is first line. Most patients improve within 1–3 weeks of regular exercise StatPearls. The doses below are starting points; adjust to irritability.

Escalate to a doctor if there is no meaningful change after 3–4 weeks of adherent conservative care, if a neurological deficit appears, or if the diagnosis is in doubt. Options there include imaging, an image-guided local anaesthetic or corticosteroid injection, botulinum toxin, and, rarely, surgical release.

Sitting is the load these patients cannot avoid: often 6–10 hours a day at a desk, in a car or on transport. On a hard seat the body weight concentrates on a small contact area under the ischial tuberosities, right beside the sciatic nerve in the deep gluteal space. Hours of that sustained compression keep the tissue irritable between sessions.

Viscoelastic memory foam lets the pelvis sink in, increasing the contact area and lowering peak interface pressure: the same principle of pressure redistribution used in seating for pressure-injury prevention. For this patient it means less compression over the piriformis and nerve through the day, which supports what you do in the clinic.

Evidence, honestly: the rationale is mechanical. No trial has tested Frido cushions, or seat cushions in general, as a treatment for piriformis syndrome. Recommend one as an adjunct to load management when sustained sitting is a clear aggravating factor in your findings, not on its own.

Default: the Frido Cloud Seat Cushion. It has the thickest memory foam (2 in), the widest pressure spread and a sloped front edge that offloads the posterior thigh along the nerve's course. Put it on the chair the patient sits on longest.

Prices as listed on myfrido.com on 14 Oct 2026; check the product page for today's price.

Setting it up with the patient

• Sit fully back so the pelvis is on the cushion, not perched on the front edge. On the Cloud, the sloped edge faces forward.
• Recheck after adding it: hips level with or slightly above the knees, feet flat (add a footrest if needed), elbows at desk height, screen at eye level.
• Drivers: recheck pedal reach, headroom and mirrors before driving.
• The cushion does not replace breaks: keep standing every 30–45 minutes.

In the Frido Care app, add a cushion to the plan only when your findings show sitting load is a driver; you accept, edit or drop every suggestion. Frido ships it to the patient directly, or they collect it at a Frido store.

Explain it in plain words

"Your pain isn't coming from your spine. There's a small muscle deep in your buttock, and the main nerve to your leg runs right beside it. When the muscle gets tight, it squeezes the nerve, and you feel it down the leg. Sitting for hours presses on that spot, so we'll take the pressure off while we loosen and strengthen the muscle."

What to say about the cushion, and what not to

Frido does not claim any of these cushions treats sciatica or piriformis syndrome. None has a tailbone cut-out.

Exercise demos to send

Every exercise in the plan above, with a short demonstration video and written steps. Send the ones you prescribe, with your own dose.

Demonstrations: Physitrack home exercise videos.

Send the patient view

The patient view of this protocol has the explainer, the home plan from Phase 1 and the safety-net in plain words, and leaves out everything clinical. Send it with Send patient view at the top of this page, or switch to it with the toggle to go through it together in the session.