The Clinical Syndrome

Bursae are formed from synovial sacs, whose purpose is to allow the easy sliding of muscles and tendons across one another at areas of repetitive movement. Lining these synovial sacs is a synovial membrane invested with a network of blood vessels that secrete synovial fluid. With overuse or misuse, the bursa may become inflamed or, rarely, infected; inflammation of the bursa results in an increase in the production of synovial fluid that causes swelling of the bursal sac. Although significant interpatient variability exists in the number, size, and location of bursae, the ischial bursa generally lies between the gluteus maximus muscle and the bone of the ischial tuberosity. It may exist as a single bursal sac or, in some patients, as a multisegmented series of loculated sacs.

The ischial bursa is vulnerable to injury from both acute trauma and repeated microtrauma. Acute injuries are often caused by direct trauma to the bursa from falls onto the buttocks and from overuse, such as prolonged riding of horses or bicycles ( Fig. 101.1 ). Running on uneven or soft surfaces such as sand also may cause ischial bursitis. If inflammation of the ischial bursa becomes chronic, calcification may occur.

The ischial bursa is vulnerable to injury from both acute trauma and repeated microtrauma. Acute injuries are caused by direct trauma to the bursa from falls onto the buttocks and from overuse, such as prolonged riding of horses or bicycles.

Signs and Symptoms

Patients suffering from ischial bursitis frequently complain of pain at the base of the buttock with resisted extension of the lower extremity. The pain is localized to the area over the ischial tuberosity; referred pain is noted in the hamstring muscle, which may develop coexistent tendinitis. Often, patients are unable to sleep on the affected hip and may complain of a sharp “catching” sensation when extending and flexing the hip, especially on first awakening. Physical examination may reveal point tenderness over the ischial tuberosity ( Fig. 101.2 ). Passive straight leg raising and active resisted extension of the affected lower extremity reproduce the pain. Sudden release of resistance during this maneuver causes a marked increase in pain; this increase in pain is considered a positive resisted hip extension test, a finding supporting the diagnosis of ischial bursitis ( Fig. 101.3 ).

Physical examination of the patient suffering from ischial bursitis will reveal point tenderness over the ischial tuberosity.

The resisted hip extension test for ischial bursitis.

(From Waldman SD. Physical diagnosis of pain: an atlas of signs and symptoms . Philadelphia: Saunders; 2006:309.)