Prepatellar bursitis is an inflammation, swelling, and enlargement of the prepatellar bursa. This bursa is one of several around the knee (others include the infrapatellar, supra patellar, popliteal, and pes anserinus bursa) (Fig. 16-1). It can result from frequent kneeling or from acute trauma to the anterior knee (Fig. 16-2). Often, it is only painful when kneeling directly on it.

Aseptic, inflammatory prepatellar bursitis can evolve into pyogenic prepatellar bursitis. The synovial fluid within the prepatellar bursa provides an excellent medium for bacterial growth, and the bursa can be inoculated by direct trauma or abrasions to the overlying skin.

Focal swelling on the anterior surface of the knee overlying the patella and the patellar tendon is normally seen. Often the borders of the patella are unrecognizable. More diffuse swelling and pain about the knee should raise suspicion for an intrinsic problem within the knee. Pain is unusual with prepatellar bursitis unless infected. Erythema suggests septic bursitis.