What is the anatomy of the pelvis relevant to piriformis syndrome?

Updated: Dec 21, 2018
  • Author: Shishir Shah, DO; Chief Editor: Sherwin SW Ho, MD  more...
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The function of the piriformis muscle is to externally rotate and abduct the thigh. The sacral plexus is closely associated with the anterior surface of the piriformis muscle. The lumbosacral trunk and the ventral rami of the first 3 sacral nerves form the sacral plexus. The sciatic nerve passes inferior to the piriformis muscle.

The sciatic nerve exits the pelvis via 4 routes: (1) The nerve passes anteriorly to the piriformis between the rims of the greater sciatic foramen. (2) The peroneal portion of the sciatic nerve passes through the piriformis; the tibial portion passes anterior to the piriformis muscle. (3) The peroneal branch of the sciatic nerve loops above and posterior to the piriformis muscle, whereas the tibial branch passes anterior to the piriformis muscle. (4) The undivided sciatic nerve penetrates the piriformis muscle.

Dysfunction of the piriformis muscle can cause signs and symptoms of pain in the sciatic nerve distribution, that is, in the gluteal area, posterior thigh, posterior leg, and lateral aspect of the foot. [1]

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