Piriformis Test

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Definition/Description

The Piriformis test is a lower limb provocation test to evaluate the impact of the piriformis muscle on the sciatic nerve. 

Clinically Relevant Anatomy

Piriformis is a flat muscle and is one of the hip lateral rotators. The origin is on the anterior side of the sacrum and has an insertion at the superior aspect of the greater trochanter of the femur. The piriformis muscle is running over the top of the sciatic nerve. This muscle has the function of external rotation, abduction, and extension in the hip and it also plays an important role to stabilize the hip joint. The piriformis muscle is innervated by the direct branches from the sacral plexus (L5-S2). 

Sciatic nerve or also named as N. Ishiadicus passes behind the hip joint to the muscles lying underneath. Above the knee joint, the sciatic nerve splits into two branches: Tibialis nerve and the Common Peroneal nerve. The sciatic nerve passes over or under the piriformis muscle but it is also possible that the sciatic nerve passes, partially or whole, through the piriformis muscle. This depends from person to person.

Purpose

The piriformis test is used to screen the piriformis muscle and to detect tightness of the muscle or other discomforts of the sciatic nerve as it passes through or under the Piriformis muscle. Because this is a muscle and neurological test.

Technique

The Piriformis test can be performed in two methods:

1. Piriformis test in side-lying position: For performing the test, the patient is positioned in side-lying on the unaffected side. The symptomatic leg is positioned in 60 to 90 degrees of flexion in the hip and 90 degrees flexion in the knee joint. The patient should be lying with the face directed towards the examiner, the examiner’s hand is placed on the pelvis to stabilize it, The other hand is placed on the lateral side of the knee. The examiner gives hand pressure on the lateral side of the knee and tries to stretch the part as far as possible. The examiner performs horizontal adduction while putting pressure on the knee in the direction of the table. During the stretch, the patient may feel pain or discomfort. This test is also named as the FAIR test (Flexion Adduction and Internal Rotation).
2. Seated Piriformis Test: The piriformis test can also be examined in a seated position on the chair with back upright and feet resting on the ground. The test is performed by crossing the affected leg and placing the ankle of the affected leg on the unaffected knee. One hand of the examiner is at the ankle to stabilize the part while the other hand is placed on the lateral side of the knee. The patient is then asked to bend forwards o feel the stretch in the gluteal region or the examiner pulls the knee towards the chest.

Results of the test

The patient may complain of pain in the piriformis muscle region or the gluteal region, The pain may increase suddenly and there could also be a pain in the posterior aspect of the thigh. This indicates that the pain is because of the piriformis muscle tightness and the sciatic nerve is not directly involved by the lumbar disc herniation. There could be pain in the buttock and throughout the course of the sciatic nerve that is the posterior part of thigh and leg then this indicates that the sciatic nerve has become pinched by the piriformis muscle. The positive result of the test indicates Piriformis syndrome. Although the pain could be because of both the piriformis muscle and a lumbar disc herniation which can be identified by performing the Straight Leg Raising Test. The Freiburg sign also stretches the piriformis muscle where, in the supine lying position, the hip is passively medially rotated and extended. There is burning pain felt in the gluteal region and also throughout the course of the sciatic nerve signalling that the sciatic nerve has been irritated by the pinching of the piriformis muscle. This is also an indication of Piriformis syndrome. In this syndrome, we speak of pain or numbness in the buttock and posterior thigh with occasional radiation into the foot. Another possible cause for the clamping of the sciatic nerve are trigger points in the piriformis muscle.

Key Research

The piriformis test has been proved to be reliable and valid as a clinical test for sciatic nerve entrapment in the gluteal region by a study conducted by Hal D. Martin et al. There are other combination studies also available that determines the piriformis test is reliable and valid for the diagnosis of Piriformis syndrome.

Resources

• Piriformis Syndrome
• Diagnosis and Management of Piriformis Syndrome
• FAIR test