Assessment and evaluation
Symptoms most commonly felt from piriformis syndrome include pain or paresthesia in the buttock and along the sciatic-nerve distribution, sometimes all the way to the foot. Most muscles of the posterior thigh, anterior and posterior leg, and foot, are innervated by the sciatic nerve. Therefore, compression of the sciatic nerve in piriformis syndrome may produce pain or weakness in many different muscles.

The superior gluteal nerve is responsible for innervating the gluteus minimus and medius and the tensor fascia latae muscles. Since these muscles are all abductors of the hip, compression of the superior gluteal nerve will often cause weakness of the hip abductors. Hip-abductor weakness can be observed with the presence of a Trendelenburg sign.

For example, if you suspect the problem is on the right side, have the client stand on the right leg and then lift all weight off the left leg by bending the left knee. If the pelvis tilts downward to the left side when the left foot is lifted off the ground, there is evidence of weakness in the hip-abductor muscles on the right side. This weakness may be resulting from compression of the superior gluteal nerve by the piriformis muscle.

The inferior gluteal nerve innervates the gluteus maximus muscle. If this nerve is being compressed, weakness may be perceived in the gluteus maximus, the strongest hip extensor. Because of the size of the gluteus maximus, atrophy due to nerve compression may be apparent during observation. If the inferior or superior gluteal nerves are being compressed, pain is likely to be limited to the buttock region. Compression of the sciatic nerve is also likely to produce symptoms down the back of the leg.

Sitting for prolonged periods usually aggravates symptoms of piriformis syndrome. Some other activities may also aggravate the pain if the piriformis muscle is being used extensively. It may be overworked by either excessive concentric or eccentric activation, most often associated with rotary movements of the hip.

Palpation of the gluteal region gives additional clues about piriformis syndrome. When the piriformis is hypertonic, it can be palpated as denser and harder than the surrounding muscles. The piriformis can be found by connecting a point halfway along the sacrum to the superior surface of the greater trochanter of the femur.

There are several physical-examination procedures that can be used to help identify piriformis syndrome. The most common procedure is the side-lying piriformis test. This test is performed with the client on his/her side with the hip flexed to approximately 90 degrees. The thigh is then brought into a position of horizontal adduction as far as it can comfortably go. The practitioner is attempting to see if this position will recreate any of the symptoms the client has been experiencing. If it does, it is likely that some compression exists on the sciatic nerve by the piriformis muscle. It has also been found that a resisted lateral hip rotation while the hip is in full medial rotation (piriformis muscle in a stretched position) may reproduce the symptoms if piriformis syndrome is present.

Another useful examination procedure is the seated piriformis test. In this procedure, a contraction of the piriformis muscle is engaged while the client is in a seated position. The practitioner places his/her hands on the lateral side of the client's knees, and resists the client's attempt to horizontally abduct (spread) the thighs. If this motion reproduces the client’s discomfort, there may be piriformis involvement. There may also be some weakness evident on the affected side when performing this procedure as well.

Note that when the hip is flexed to 90 degrees, the piriformis is a horizontal abductor of the thigh. Therefore, the first side-lying piriformis test stretches the muscle as the hip is adducted, and the second (seated) piriformis test contracts the muscle in horizontal abduction against resistance.

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