Septic Arthritis, Osteomyelitis, and Pyomyositis in a Previously Healthy Infant.

Septic arthritis of the shoulder is rare in the pediatric population. In younger children and infants, it can be very difficult to diagnose. Septic arthritis of the shoulder is more commonly associated with concurrent osteomyelitis when compared to septic arthritis of the lower extremity. We describe a case of a 9-month-old patient with septic arthritis, osteomyelitis, and pyomyositis of the shoulder, and a discussion of diagnosis and management of pediatric bone and joint infection in the emergency department setting.