A 55-year-old man had a 2-day history of knee pain. Swelling was visible over the patella, and fluctuation was felt on palpation. The skin over the knee was warm an reddish. After cleansing the skin with chlorhexidine a needle is inserted perpendicularly into the bursa, while the bursa is grasped with a ring-shaped grip to press the fluid into the centre of the bursa. Ultrasonography demonstrates how the fluid collection becomes thicker when pressed from the sides. The fluid leukocyte count was 1600/cubic millilitre, and the majority were polymorphonuclear. Staphylococcus aureus was cultured from the fluid. Serum CRP was 43 mg/dl. The patient was treated with intravenous cefuroxime for the first 24 hours, followed by peroral cephalexine. If bacterial bursitis is suspected, antibiotics should be started without waiting for bacterial culture results. Even a slightly increased leukocyte count in the bursal fluid suggests bacterial infection . In aseptic bursitis the cell count is very low (often below 300).
Bacterial prepatellar bursitis