Osteomyelitis of the patella is an uncommon infection that is primarily a disease of childhood. The diagnosis frequently is delayed because of its rarity and variable presentation, which may be acute with systemic signs or insidious with mild local signs. The diagnosis should be considered in patients with persistent peripatellar pain and swelling, cellulitis, septic prepatellar bursitis, and septic arthritis of the knee that does not respond to standard treatment. Treatment is identical to the treatment of osteomyelitis at other locations. The outcome is favorable in the child regarding range of motion and activity, although there may be persistent changes radiographically.