Septic Bursitis · What Is It, Causes, Treatment, and More

Septic bursitis, or infectious bursitis, refers to the infection and subsequent inflammation of a bursa (plural: bursae). Bursae are small, fluid-filled sacs that cushion and lubricate joints, the areas where different tissues (e.g., muscles, tendons, and bone) rub against each other. Bursae provide a smooth gliding surface that reduces friction between these structures to ensure that movement is easy and painless. 

There are over 150 bursae located all over the body. The major bursae are found near large joints, such as the shoulder, elbow, hip, and knee. Bursae are lined with a thin outer membrane (i.e., the synovial membrane) that produces a small amount of lubricating bursal fluid. When bursitis occurs, the synovial membrane becomes thickened and produces excessive fluid, which causes painful swelling of the bursa. The most common causes of bursitis are overuse from a repeated motion, direct injury, infection, and certain types of metabolic or inflammatory joint disorders (e.g., gout or rheumatoid arthritis). When bursitis is caused by an infection, it is known as septic bursitis.

Septic bursitis is caused by the infection of a bursa and typically affects superficial bursae that lie just beneath the skin (e.g., olecranon bursa of the elbow, prepatellar bursa of the kneecap). Because of their location, microorganisms can more easily gain entry to the superficial bursae through a cut, scrape, puncture, bug bite, or other trauma to the skin. As a result, most cases of septic bursitis are caused by bacteria living on the skin’s surface (e.g., Staphylococcus aureus, the Streptococcus species). 

Septic bursitis is most likely to occur when an individual engages in occupational or recreational activities that increase risk of injury to bony prominences, like the elbow and knee. For instance, olecranon bursitis is commonly seen in individuals who spend a lot of time leaning on their elbows (e.g., plumbers, carpenters, students) and in athletes who frequently land with their elbows onto hard surfaces (e.g., volleyball players). Similarly, prepatellar bursitis may occur in people who spend a lot of time kneeling or crawling, like carpet layers, clergy, gardeners, or household cleaners. When bursitis develops in the knee, it is sometimes referred to as “clergyman’s knee” or “housemaid’s knee.” 

Less often, septic bursitis can develop in deep bursae located between bone and muscle (e.g., trochanteric bursa of the hip, subacromial bursa of the shoulder). In such cases, the infection often results from a previous medical intervention, like a surgery, a corticosteroid injection, or a joint aspiration, in which fluid is removed from a joint space. In other cases of deep septic bursitis, the infection may start in a nearby area of the body or the blood and then spread to the bursa.

Although septic bursitis can occur in otherwise healthy individuals, up to half of cases occur in individuals who have compromised immune systems or underlying systemic conditions (e.g., diabetes, kidney disease, alcoholism, etc.).

Unlike aseptic bursitis, which is not infectious, septic bursitis is a potentially serious condition that requires prompt medical treatment to resolve. If not treated appropriately, the infection can spread nearby to other joints, soft tissues, and bone. In addition, untreated bursitis can result in permanent thickening and enlargement of the affected bursa, which could reduce the joint’s range of motion and cause pain with active movement. At its worst, septic bursitis can lead to overt sepsis or septic shock, a life-threatening illness that can cause decreased blood pressure, organ failure, stroke, altered mental status, and death.

Symptoms of septic bursitis include pain over the affected bursa, joint stiffness, swelling, localized tenderness, and fever. If the infected bursa is close to the skin’s surface, the overlying skin may be red and feel warm to the touch. Swelling and skin redness are less common when inflammation occurs in the deeper bursae. 

Diagnosis of septic bursitis begins by taking a thorough medical history and conducting a physical examination. Symptoms of bursitis often resemble those of other medical conditions, so additional laboratory tests, often including bursal aspiration, are usually needed to confirm the diagnosis.  

Bursal aspiration is a procedure that involves using a thin needle to remove a small amount of bursal fluid for analysis. Identification of pathogenic bacteria or other microorganisms in the bursal fluid can confirm the diagnosis of septic bursitis. Analysis of the bursal fluid can also assist in ruling out other medical conditions, such as gout or septic arthritis (i.e., infection of the joint tissues). In addition, removal of a small amount of bursal fluid can help relieve the pressure and pain caused by the swollen bursa. Finally, imaging with ultrasound, computerized tomography (CT), or magnetic resonance imaging (MRI) may be helpful in certain cases to confirm the presence of swelling and potential involvement of nearby tissues. 

Septic bursitis is a medical emergency that requires prompt treatment with broad-spectrum antibiotics (e.g., cephalosporins, clindamycin, or vancomycin). Mild cases of septic bursitis can be treated with oral antibiotics, while severe cases may require intravenous (IV) antibiotics. Drainage of the bursal fluid, usually performed with a needle and a syringe (i.e., needle aspiration), may also be a treatment option. This procedure may be repeated several times over the course of a few days until the infection is resolved. In cases where antibiotic treatment and aspiration do not resolve the infection, surgical drainage of the bursa may be performed. Finally, in the rare cases in which the infection has spread to nearby tissues, treatment may include a bursectomy, the surgical removal of the affected bursa.

Septic bursitis occurs when a bursa becomes infected and inflamed. Infection is usually a result of bacteria entering the bursa through a cut, scrape, or other trauma to the skin, but the infection can also start in the blood or nearby tissues and spread to the bursa. Septic bursitis most commonly affects bursae located in the elbow and knee joints due to their superficial locations. Symptoms of septic bursitis include pain over the affected bursa, joint stiffness, swelling, localized tenderness, fever, and if the bursa is superficial, redness and warmth of the overlying skin. Diagnosis of septic bursitis generally involves aspiration and analysis of the bursal fluid. Treatment includes broad-spectrum antibiotics, as well as drainage of the bursal fluid through needle aspiration. In severe cases, surgical drainage or removal of the bursa may be necessary in order to resolve the infection completely.