Instead of blood or inflammatory fluid in the bursa, pus fills the bursa. The area around the bursa becomes hot, red and very tender. It may be very difficult to kneel down and put the knee on the floor due to the tenderness and swelling. The bursa sack may swell and fill with fluid at times. This usually related to your activity level.
More activity usually causes more swelling.
In people who are on their knees a lot, like carpet layers, the bursa can get to be very thick, a lot like a kneepad in front of the knee. Finally, if the bursa becomes infected, the front of the knee becomes swollen, very tender and warm to the touch around the bursa. You may run a fever and begin to chill. An abscess may form on the front of the knee and drain pus if the infection is not treated fairly quickly. The diagnosis of pre-patellar bursitis is usually obvious from the physical examination.