Piriformis Syndrome and the Deep Hip

Most sciatica starts at the spine. This page is about the minority that does not — the buttock-and-leg pain whose address is a small, deep muscle in the hip called the piriformis, which the sciatic nerve has to pass beneath on its way out of the pelvis. Piriformis syndrome has been described for the better part of a century and argued about for nearly as long: the literature is mostly case series, nobody has a clean number for how common it is, and its signature features overlap with half a dozen other reasons a buttock can hurt. What the evidence does agree on is worth knowing, because it changes what a physical therapy plan is built to do.

Where it lives

Piriformis runs from the front of the sacrum out through the greater sciatic notch to the top of the thigh bone. It is a hip rotator: it turns the thigh outward when the hip is straight and helps pull it sideways when the hip is bent. The sciatic nerve — the largest nerve in the body, formed from the lower spinal nerve roots — leaves the pelvis through the same notch, almost always emerging just below the muscle’s lower edge. That shared doorway is the whole anatomy of the problem. A piriformis that is thickened, in spasm, shortened, or irritated by a fall or by hours of sitting on a hard edge can press on or inflame the nerve beneath it, and the nerve reports the trouble the only way it knows how: as pain down its territory, the back of the thigh and sometimes the calf.

For decades the favorite explanation was an anatomical variant: in roughly one person in six, the nerve or one of its two divisions pierces the muscle rather than passing beneath it. That figure is real — a pooled analysis of more than six thousand cadavers put it at about 17% — but the same review found the variant no more common in people operated on for piriformis syndrome than in the general population. The nerve’s route, in other words, is mostly not the culprit. What the muscle is doing matters more than where the nerve threads through it.

The quartet

Because there is no blood test, no imaging finding, and no single physical test that settles the diagnosis, clinicians recognize piriformis syndrome by pattern. The two systematic reviews of the world’s reported cases — one covering 55 studies, and an update eight years later — kept finding the same four features: pain in the buttock itself rather than centered on the low back, pain that worsens with sitting, tenderness when the examiner presses over the greater sciatic notch, and pain reproduced by maneuvers that stretch or contract the piriformis. The best-known of those maneuvers folds the hip up, across, and inward — flexion, adduction, internal rotation, the “FAIR” position — which wraps the muscle tightly over the nerve.

Two honest caveats travel with the quartet. First, a positive straight-leg raise, the classic disc test, does not rule piriformis syndrome out; the updated review found it limited in a substantial share of cases. Second, the accuracy of every one of these signs is unproven, because the studies that could prove it — comparing sciatica patients with and without disc disease, blind to the answer — have barely been done. The diagnosis is, as one review put it, roughly where the herniated disc was a generation ago: clearly real, poorly measured. A careful clinician therefore treats it as a diagnosis of pattern and exclusion — checking the spine, the sacroiliac joint, the hip joint, and the hamstring tendons before pinning it on the piriformis — and a broader label, deep gluteal syndrome, now covers every way the nerve can be caught in that space, of which piriformis is only the most famous.

What physical therapy is built to do

The first-line answer, across every review, is conservative care led by physical therapy. The 2023 systematic review of treatment trials is candid about why: thirteen studies, 508 patients, mostly comparing one injection to another, and quality low enough that no single conservative treatment could be recommended over any other. Its conclusion was to follow the general guidelines for back pain and sciatica — physiotherapy first — with surgery reserved for a chronic minority. That is less an endorsement of any particular exercise than a statement about where the burden of proof sits.

What a good program actually contains follows from the anatomy. A therapist works on three fronts at once. The first is the muscle itself: stretching piriformis and the surrounding rotators, typically in that same FAIR direction, and easing the spasm and guarding around it. The second is the reason the muscle was overworking, which is usually the hips around it — weak or slow gluteal muscles, a stiff hip joint, a pelvis that drops on one side when you stand on one leg — so progressive strengthening of the hip abductors and rotators is the part of the plan that tends to last. The third is the nerve: gentle mobilization that slides the sciatic nerve through its tunnel, and a hard look at the sitting that provoked everything — the wallet in the back pocket, the low chair, the hours in the car. Like every paced program, it starts below the flare line and progresses by plan.

The largest outcome series ever published on this condition is encouraging about that kind of care. Over ten years, a New York rehabilitation group followed 918 patients diagnosed by a nerve test in the FAIR position; among those who tested positive and were treated with an injection plus physical therapy, 79% improved by half or more, with average improvement around 71% at ten months, and only about one in fifteen went on to surgery. It is a before-and-after series, not a randomized trial, and the injection is bundled in with the exercise — but it is the clearest picture anyone has of how this condition behaves when the deep hip is treated as the target.

When the plan needs more

When a well-run program stalls, the next layer is a targeted injection into the muscle — local anesthetic with a steroid, or botulinum toxin to relax it for months at a time — usually guided by ultrasound so the needle finds a small muscle sitting under a large one. Trials of these injections are the bulk of the treatment evidence, and only a few reached a clinically meaningful reduction in pain, which is why they are positioned as a way to let the exercise work rather than as a plan in themselves. Surgical release of the muscle exists for the rare chronic case that has exhausted everything else; the surgical case series show before-and-after improvement, and the reviews describe it as “may have a place” rather than as a destination. Nerve-pain medications are used case by case, as they are for any neuropathic pain, with the same modest expectations.

When to bring in a specialist

Buttock-dominant pain that has outlasted six to eight weeks of first-line care, pain that keeps you from sitting through a working day, or any weakness, numbness, or change in bladder or bowel control are reasons to be seen — the last of those urgently, because it points to the spine, not the hip. A pain physician or a physiatrist can sort out which of the overlapping causes you have, arrange the guided injection if the program needs it, and keep the plan honest about what it is treating. The work of the diagnosis is mostly the work of ruling other things out; that is a job for a clinician, with your history and an examination, and not for a page.