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What is piriformis syndrome?

Piriformis syndrome and ultrasound-guided injection therapy

Piriformis syndrome is a condition characterised by pain in the buttock at the site of the piriformis muscle. The muscle is believed to irritate the adjacent sciatic nerve, resulting in this syndrome.

Piriformis muscle-relevant anatomy

The muscle is located at the back of the hip, deep in the buttock region. The muscle is one of the external hip rotators (rotate the hip to the outside). The sciatic nerve is a major nerve that supplies the thigh and lower leg. It passes deep in the buttock and then leaves the area by exiting under the piriformis muscle.

What are the causes of piriformis syndrome?

It is believed that the main cause of this syndrome is irritation of the sciatic nerve as it passes adjacent to the piriformis muscle. This could be due to tightness of the piriformis muscle or altered anatomy resulting in a small space for the sciatic nerve, predisposing for nerve compression. There are well-recognised variations in the anatomy in this area, and sometimes the sciatic nerve branches are tethered/pass between the piriformis muscle fibres. This may result in the symptoms of piriformis syndrome.

How do I know if I have piriformis syndrome?

The clinical features of piriformis syndrome include:

  • Deep buttock pain that can extend into the thigh and lower leg.

  • The pain can be associated with a pins and needles sensation within the thigh and lower leg along the course of the sciatic nerve.

  • Applying pressure over the area of the piriformis muscle usually results in tenderness and reproduces the pain.

What other conditions can mimic piriformis syndrome?

Piriformis syndrome is not a common condition; generally, it is “a diagnosis of exclusion”. This means that the diagnosis of piriformis syndrome is considered when other more common causes of pain in the back/buttock area have been ruled out. These include:

  • Hip osteoarthritis.

  • Sciatica refers to pressure on the sciatic nerve roots as they leave the spine. This is usually secondary to disc problems and/or arthritic changes within the spine.

  • Hamstring tendonitis.

  • Sacroiliac joint pain refers to pain and inflammation coming from a particular joint in the buttock area. To find out more, please see our article about Sacroiliitis.

How to diagnose piriformis syndrome?

Imaging is very useful in the assessment and ruling out other causes of back/buttock pain. An MRI scan of the lower (lumbar) spine and the hip/pelvis will be useful. This will assess any pressure upon the sciatic nerve roots as they emerge from the spine. Furthermore, it will assess the piriformis muscle and the adjacent sciatic nerve in the buttock area. Nerve conduction studies might also be helpful.

What is the treatment for piriformis syndrome?

Piriformis syndrome can be challenging to manage, and the available treatment options may work differently for patients. The treatment usually starts with physiotherapy. This includes hip muscle strengthening exercises and stretching exercises to reduce piriformis muscle tightness. Soft tissue manipulation can also be helpful.

Can ultrasound-guided steroid injection help in piriformis syndrome?

If the results from the above steps are unsatisfactory, then an ultrasound-guided piriformis muscle cortisone injection can help with the treatment. This aims to reduce the pain from the piriformis muscle and the sciatic nerve irritation, to help with the rehabilitation program. The injection usually involves a local anaesthetic (numbing medicine) and a low-dose corticosteroid. The injection can also act as a test. If you notice good results after the injection, this would confirm the diagnosis of piriformis syndrome. Please read our article to find out more about steroid injections around the hip.

It is essential to perform piriformis syndrome injections under ultrasound guidance. The piriformis muscle is a deep structure, and ultrasound allows for accurate visualisation of the needle to ensure that the injection is effective and the procedure is safe and efficient

What other treatment options are available for piriformis syndrome?

Other treatment options for piriformis syndrome include Botox injection into the muscle and surgical treatment. The latter is rarely needed and aims to surgically decompress the sciatic nerve as it passes deep into the piriformis muscle.

Hip conditions and treatments


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Specialist Consultant Musculoskeletal Radiologist Doctor with extensive experience in image-guided intervention

To book a consultation:

Call us on 020 3442 1259 or Book online

The Musculoskeletal Ultrasound & Injections clinic

Healthshare West London (The Riverside) Clinic
Unit 3, Brentside Executive Park

Brentford, TW8 9DR

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