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

What is piriformis syndrome?

Piriformis syndrome is a neuromuscular condition. 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 wider term "deep gluteal syndrome". This 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 turn your hip outward. When it becomes tight, swollen or goes into spasm, it can squeeze the sciatic nerve. The nerve runs just beneath the muscle, or in some people, right through it.

Sciatica, on the other hand, is a symptom rather than a diagnosis on its own. It describes pain along the path of the sciatic nerve. It is most often 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 leaves the spine. You can read more 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 spread down the back of the thigh. It often feels very like sciatica. That is exactly why the two are so often confused.

You may also notice tenderness when you press into the middle of the buttock, or discomfort when climbing stairs. Some people find the pain eases with walking but flares up 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 come from the sacroiliac joint, which sits right next to the piriformis. SI joint dysfunction can cause very similar buttock and thigh pain. This makes the picture even more complex. Buttock pain linked to sitting can also come from ischial bursitis, an inflamed bursa under the sitting bone.

Because the symptoms overlap so much, a clinical examination alone may not give a clear answer. That is where imaging plays a vital role.

What causes piriformis syndrome?

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

How the body compensates is important here. Your body is a connected chain from your feet up to your head. Your pelvis may sit unevenly, perhaps from a small difference in leg length or a rotated sacrum. Then the piriformis on one side works overtime to keep you stable. 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 problem somewhere else entirely.

How does a standing scan help diagnose piriformis syndrome?

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

When you lie down for a usual 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 is missed.

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

If the scan shows a level pelvis and a normal lumbar spine, your clinician can focus with confidence on the piriformis itself. They can then guide you towards the right soft-tissue tests or treatment. If it shows 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, your treating clinician may consider a range of approaches.

• Targeted stretching. A piriformis stretch is commonly recommended to ease tightness. In this stretch, you gently pull the knee of the affected side across towards the opposite shoulder. Your physiotherapist can tailor a programme for you.
• Changing your activities. Avoiding long periods of sitting, using a cushion to reduce direct pressure, and taking regular breaks to move 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. A standing scan may show a pelvic tilt or rotation that is overloading the piriformis. If so, correcting that underlying imbalance may form part of the treatment plan your clinician recommends.

Before you start treatment, or change the treatment you are on, it is worth getting a detailed diagnosis. Knowing whether the cause sits in the pelvis, the legs or the spine changes what will actually help.

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

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