Piriformis syndrome is a clinical condition of sciatic nerve entrapment at the level of the ischial tuberosity. While there are multiple factors potentially contributing to piriformis syndrome, the clinical presentation is fairly consistent, with patients often reporting pain in the gluteal/buttock region that may "shoot," burn or ache down the back of the leg (i.e. "sciatic"-like pain). In addition, numbness in the buttocks and tingling sensations along the distribution of the sciatic nerve is not uncommon.
The sciatic nerve runs just adjacent to the piriformis muscle, which functions as an external rotator of the hip. Hence, whenever the piriformis muscle is irritated or inflamed, it also affects the sciatic nerve, which then results in sciatica-like pain. The diagnosis of piriformis syndrome is not easy and is based on clinical history and presentation. Other conditions that can also mimic the symptoms of piriformis syndrome include lumbar canal stenosis, disc inflammation, or pelvic causes.