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The pear-shaped muscle and back pain
Last reviewed: 04.07.2025
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Piriformis muscle - m. piriformis
When the leg is free from support, the piriformis muscle exhibits great strength: by contracting it, the thigh can be turned outward. It abducts the thigh bent at 90°.
- Origin: Facies pelvina of the sacrum
- Attachment: apex of Trochanter major.
- Innervation: spinal nerves S1-S3 - sacral plexus - rr. musculares.
Diagnostics
Trigger zones are most often localized: in the lateral part of the muscle; in the medial part of the muscle near the sacrum. Examination of the lateral rotator muscle group of the hip is complicated by the fact that they lie under the gluteus maximus. The piriformis muscle can be examined along its entire length, and the medial end is accessible for almost direct examination through the rectum or vagina. Localization of the piriformis muscle is determined by external examination along the piriformis line from the greater trochanter to the cranial edge of the greater sciatic foramen. When the gluteal mouse is relaxed, the greater trochanter can be determined by deep circular palpation of the lateral surface of the thigh. The inner edge of the greater sciatic foramen along the lateral edge of the sacrum can be palpated through the relaxed gluteus maximus muscle downwards from the posterior inferior iliac spine. Trigger zones of the lateral part of the muscle are usually located on the border of the middle and lateral thirds of the piriformis muscle. These trigger zones are accessible only to external palpation. The trigger zone of the medial part of the muscle manifests itself as noticeable pain with pressure in the medial direction in the area of the greater sciatic opening. When examining from the pelvis, these medial trigger zones are felt more painful. If there is doubt about the presence of trigger zones, a vaginal or rectal examination should be performed.
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Referred pain
The pain is generally referred to the sacroiliac region, buttock, and behind the hip joint. Sometimes the pain extends to the upper two-thirds of the back of the thigh. The pain pattern from the trigger points of the lateral and medial portions of the muscle is the same.