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Piriformis Syndrome
Definition: Piriformis syndrome occurs when the piriformis muscle irritates the sciatic nerve leading to sciatica.
Causes: There is a significant variance amongst individuals in the distribution of the sciatic nerve about the piriformis muscle. In some individuals, the sciatic nerve perforates the piriformis muscle, which is believed to increase the risk of piriformis syndrome. Other causes of piriformis sydrome have been linked with sacro-iliac dysfunctions, altered foot bio-mechanics, piriformis myospams, underactive glutei through reciprocal inhibition via overactive, shortened hip flexors, and overuse injury such as in cycling and rowing.
Examination: Piriformis syndrome must be differentiate from other causes of sciatica, which may be discogenic etc. Patients suffering from piriformis syndrome will usually present with pain in the gluteal region with occasional referred pain following the dermatomal distribution of the sciatic nerve. Anaesthesia, paraesthesia, asthenia, may be appreciated in this condition given that it is a lower motor neurone syndrome.
Palpation of the sciatic nerve approximately half way between the superior aspect of the greater trochanter and the posterior superior iliac spine can be exquisitely tender.
Active resisted testing of the piriformis muscle:
Usually, activation of the piriformis muscle will elicit pain in patients suffering from piriformis syndrome. Lay the patient supine with the patient's symptomatic limb flexed to 90° at the hip and knee. Passively introduce internal rotation at the hip than ask the patient to actively externally rotate. An aggravation in symptoms may indicate a piriformis syndrome.