Bursitis is an irritation or inflammation of a bursa inside the knee. Bursa are fluid filled sacs that act as a cushion between skin, tendons, ligaments and bones. There are several bursae surrounding the knee joint. Injuries are usually minor and do not demand immediate medical attention. The prepatellar bursa is normally the most susceptible to injury because it is located directly in front of the knee. Bursae at any site may be irritated from repetitive motions or impacts. This is often referred to as repetitive microtrauma.
The injury is common in runners because of repetitive leg motion, or sports like wrestling where the knees are rubbed excessively on the mat during competition. Non-surgical treatments can be used to reduce swelling and irritation, although in more extreme cases, the surgeon may remove some of the fluid from the bursa (a process known as aspiration) if it is very swollen.