Piriformis Syndrome or Sciatica: How Do You Tell the Difference?

What is piriformis syndrome?

Piriformis syndrome is a neuromuscular condition where the piriformis muscle, a small flat muscle deep in the buttock, presses on or irritates the sciatic nerve as it passes through the deep gluteal space. It is sometimes grouped under the broader term "deep gluteal syndrome," which covers any structure in that area that can trap the nerve.

The piriformis muscle runs from the front of the sacrum (the triangular bone at the base of your spine) across to the top of the thigh bone. Its job is to help rotate your hip outward. When it becomes tight, swollen or goes into spasm, it can squeeze the sciatic nerve that runs just beneath it, or in some people, right through it.

Sciatica, by contrast, is a symptom rather than a standalone diagnosis. It describes pain along the path of the sciatic nerve, most commonly caused by a compressed or irritated nerve root in the lumbar spine. Common spinal causes include disc bulges, narrowing of the spinal canal, or bony changes that press on the nerve root where it exits the spine. You can read more about this in our guide to sciatica or a spinal alignment problem.

What are the symptoms of piriformis syndrome?

The main symptom is a deep, aching pain in the buttock that can radiate down the back of the thigh. It often feels very similar to sciatica, which is exactly why the two are so often confused.

You may also notice tenderness when pressing into the mid-buttock area, or discomfort when climbing stairs. Some people find the pain eases with walking but flares when they stop and sit down.

How do you tell the difference between piriformis syndrome and sciatica?

The key difference is where the sciatic nerve is being irritated. In spinal sciatica (often called lumbar radiculopathy), the nerve root is compressed as it leaves the lumbar spine. In piriformis syndrome, the nerve is squeezed further down, in the buttock itself.

There is a third possibility worth knowing about. The pain may relate to the sacroiliac joint, which sits right next to the piriformis. SI joint dysfunction can produce very similar buttock and thigh pain, adding another layer of complexity. And sitting-related buttock pain can also come from ischial bursitis, an inflamed bursa under the sitting bone.

Because the symptoms overlap so much, a clinical examination alone can be inconclusive. That is where imaging plays a crucial role.

What causes piriformis syndrome?

The piriformis can become tight, inflamed or go into spasm for several reasons. Often it is not a single event but a combination of factors, many of which relate to how your body is aligned under load.

The compensation narrative is important here. Your body is a connected chain from your feet up to your head. If your pelvis sits unevenly, perhaps from a subtle leg length difference or a rotated sacrum, the piriformis on one side works overtime to stabilise you. Over weeks and months, that overworked muscle tightens, and the sciatic nerve running beneath it starts to suffer. The pain you feel in your buttock or leg may actually be driven by an alignment issue somewhere else entirely.

How does a standing scan help diagnose piriformis syndrome?

A standing, weight-bearing scan shows your skeleton the way it actually works, upright and under gravity. This is the key advantage over lying-down imaging.

When you lie down for a conventional X-ray, CT or MRI, your muscles relax and your pelvis settles into a neutral position. A mild pelvic tilt or rotation that loads one piriformis more than the other can simply disappear from the image. You get a scan that looks reassuringly normal, while the mechanical cause of your pain goes undetected.

At ScanAlign, whole-body standing imaging, an EOS scan captures your full skeleton from head to ankles in a single upright image, using about 90% less radiation than a standard X-ray, around ten times less. That means your radiographer and clinician can see your spinal curves, pelvic rotation, hip alignment and leg length all at once, in the position that actually reproduces your symptoms.

If the scan reveals a level pelvis and a normal lumbar spine, your clinician can focus confidently on the piriformis itself and direct you toward the right soft-tissue investigation or treatment. If it reveals a tilt, a rotation, or a spinal cause for nerve compression, that changes the plan entirely. Either way, you leave with a clearer picture.

What helps manage piriformis syndrome?

Management depends entirely on confirming that the piriformis is the real source of the problem, not the spine or the SI joint. Once the diagnosis is clear, a range of approaches may be considered by your treating clinician.

• Targeted stretching. A piriformis stretch, where you gently pull the knee of the affected side across towards the opposite shoulder, is commonly recommended to ease tightness. Your physiotherapist can tailor a programme.
• Activity modification. Avoiding prolonged sitting, using a cushion to reduce direct pressure, and taking regular movement breaks can all help reduce flare-ups.
• Physiotherapy. Strengthening the hip stabilisers and improving pelvic control may reduce the load on the piriformis over time.
• Addressing alignment. If a standing scan reveals a pelvic tilt or rotation that is overloading the piriformis, correcting that underlying imbalance may form part of the treatment plan your clinician recommends.

ScanAlign does not provide treatment. It provides the diagnostic imaging that helps your clinician understand what is happening structurally so they can choose the most appropriate path forward. If you would like to book a standing spine and pelvis scan, we start with a free video consultation to make sure a scan is right for you.

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