Causes / typical injury mechanism: Piriformis syndrome (PS) is sciatic symptoms (burning posterior thigh and leg pain) from compression of the sciatic nerve by the piriformis muscle as the nerve exits the greater sciatic notch of the pelvis. This condition is also known as deep gluteal syndrome, as other soft tissue structures can entrap the sciatic nerve in this area. For some patients, there may be a precipitating event such as trauma.

Classic history and presentation: Individuals with PS often have a history of prolonged sitting, such as desk work, driving, cycling, or horseback riding, or a fall onto the buttocks. Clinical presentation may include low back and unilateral buttock pain, along with burning or numbness migrating down the back of the leg. The pain is typically increased with hip flexion and internal rotation.

Prevalence: Reports of incidence vary widely, ranging from 5%-36%. It is likely that PS is underdiagnosed, and cases are treated under the name of a different condition.

• Age – Most patients are between the ages of 30 and 50 years.
• Sex / gender – Reports are inconsistent; it is unclear if sex plays a significant role in PS.

Risk factors: Risk factors may include height over 180 cm (6 feet), family history, high body mass index (BMI), physically strenuous work, a sedentary lifestyle, and localized trauma.

Pathophysiology: PS is caused by piriformis muscle contractures / spasms from overuse / underuse, trauma, or hypertrophy. However, several structures could contribute to nondiscogenic entrapment of the sciatic nerve in the subgluteal space: local scar tissue or fibrous bands, other posterior hip muscles, vascular abnormalities or aberrant anatomy, and space-occupying lesions such as a tumor or hematoma.