Inflammation of bursal sacs, or bursitis, is a common condition. Bursae are fluid-filled sacs that act as cushions between tendons and either bone or skin. There are more than 150 bursae in the human body. Most cases of bursitis involve either the olecranon or the prepatellar bursa, and the majority are related to trauma. About one-third are infected and a few are secondary to inflammation associated with rheumatologic disorders. Trauma can result in both septic and nonseptic bursitis. Septic bursitis can occur as a complication of bacteremia without a history of trauma to the involved area. A common cause of septic bursitis is the injection of medication, often corticosteroids, into a bursa as treatment for nonseptic bursitis. Septic bursitis is less common in the pediatrics patient but does occur and is usually associated with acute trauma such as sports-related injuries.

Septic and nonseptic bursitis of superficial bursae such as at the olecranon and prepatellar sites may present as both red and tender (Figure 68.1). Clinical features, including fever or infection at another site, may help differentiate infected from noninfected. Bursitis of deeper bursae is usually nonseptic, but tuberculous bursitis of the greater trochanter and other sites has occurred. Microorganisms from the skin cause most infectious bursitis. Although Staphylococcus aureus is the most common single microorganism isolated from infected bursa, if introduced any microorganism (hemolytic streptococci or gram-negative bacilli) can infect these spaces.