A bursa is a thin, slippery, fluid-filled sac that serves as both a cushion and lubricant between bone and surrounding soft tissue, such as skin and muscle.Swelling and other bursitis symptoms occur when a bursa becomes inflamed.
- Previous injury
- Repetitive, prolonged kneeling
- Another underlying condition. A prepatellar bursa can become inflamed as the result of another condition, such as knee osteoarthritis, rheumatoid arthritis, gout, or pseudogout.
- Infection. About 20% of people with knee bursitis have septic bursitis, meaning a prepatellar bursa is infected.