Bursae

Bursae are small, fluid-filled sacs lined by a synovial membrane that cushion and reduce friction where bones, tendons, and muscles pass close to one another. They contain synovial fluid that lubricates moving structures.

Throughout the body, bursae are most common around joints—such as the shoulder, elbow, hip, knee, and around the base of the thumb—where they may lie between tendons and bones or between skin and bone. They can be solitary or multiple, and some communicate with the joint capsule.

Each bursa serves as a spacer that facilitates smooth movement by absorbing pressure and reducing rubbing between surfaces.

Common examples include the subacromial bursa of the shoulder, prepatellar and infrapatellar bursae near the knee, the olecranon bursa at the elbow, and trochanteric or ischial bursae in the hip region.

Inflammation of a bursa, bursitis, is usually due to overuse, repetitive stress, or prolonged pressure, but infection (septic bursitis) or inflammatory/crystal diseases can occur. Symptoms typically include localized pain, swelling, warmth, and limited joint movement.

Diagnosis is clinical, with imaging such as ultrasound or MRI used to assess the bursa and any associated effusion. Fluid aspiration may be performed to exclude infection or crystals.

Treatment is typically conservative: rest, ice, and nonsteroidal anti-inflammatory drugs; aspiration of excess fluid can relieve pressure; corticosteroid injections may be used in some cases; antibiotics are required for septic bursitis. Chronic or recurrent cases may require surgical drainage or bursectomy.

Prognosis is generally favorable with appropriate management; septic bursitis requires prompt antibiotic therapy and may need surgical intervention.