A bursa is a sac-like structure found near joints that allows soft tissues to glide across bony prominences. Bursitis is an inflammation of the bursa. Near the knee, there are three clinically important bursas: the prepatellar (in front of the patella itself), infrapatellar (just distal to the patella) and anserine (on the proximal – medial tibia). Bursitis may result from local injury, infection or systemic diseases such as rheumatoid arthritis or gout. Bursitis due to infection is known as septic bursitis.
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