There are several possible causes of knee bursitis as well as certain risk factors that make some people more likely to develop it. Common causes and risk factors include:
Previous injury. A trauma to the knee can result in damage to a prepatellar bursa, causing it to fill with blood and its lining to become inflamed. Even though the body reabsorbs the blood, the bursa lining may stay inflamed, causing knee bursitis symptoms.
Repetitive, prolonged kneeling. Bursitis is often caused by frequent "mini-traumas," which can cause the same problems as a single, more serious trauma. People who kneel a lot - people who install carpets, for example - may develop bursitis in their knees.
Another underlying condition. A prepatellar bursa can become inflamed as the result of another condition, such as knee osteoarthritis, rheumatoid arthritis, gout, or pseudogout. In these instances, the treatment for knee bursitis must accompany treatment for the underlying condition.
Infection. About 20% of people with knee bursitis have septic bursitis, meaning a prepatellar bursa is infected. Septic bursitis occurs more often in the summer months.1 Infection can reach the bursa through a cut, puncture or even an insect bite. It is possible to have septic bursitis without an obvious cut or scrape; sometimes the root cause of infection is unknown.
Certain medical conditions and medications suppress people's immune systems and make them more susceptible to septic bursitis. For example, people with cancer, HIV/AIDS, lupus, alcoholism, chronic obstructive pulmonary disease (COPD), and diabetes may be more likely to get septic bursitis.
History of inflammation of the bursa. Patients who have had bursitis in the past have an increased chance of having bursitis again.
By addressing the causes and risk factors, a person can decrease the likelihood of developing chronic knee bursitis.