An unusual case of knee pain.

Osteomyelitis of the patella is a rare disease, which primarily affects the pediatric population. We present a case of hematogenous osteomyelitis of the patella with secondary development of septic arthritis of the knee. There is often a delay in diagnosis, as illustrated by our case report, due to the rarity of the condition and nonspecific presentation. There is usually no history of trauma. Focal tenderness over the patella is the most helpful clinical sign. A small joint effusion may be present which is usually sterile and reactionary due to inflammation of the patella. Treatment of osteomyelitis of the patella is similar to treatment of osteomyelitis in other areas. Function and range of motion of the knee usually returns to normal after completion of treatment. A delay in diagnosis may lead to progression of disease and complications such as septic arthritis of the knee.