FIG 2.

Pathogenesis of osteomyelitis-associated septic arthritis. Thrombosis of the venous and arterial vascular loops in the metaphysis leads to decreased blood flow, bacterial attachment, and acute infection. (A) The physis forms a physical barrier preventing spread of the infection into the epiphysis. (B) As the infection spreads, it reaches the metaphyseal periosteum and develops a periosteal abscess. In the hip, shoulder, elbow, and ankle, the joint capsule attaches below the physis. (C) This allows the periosteal abscess to circumvent the vascular barrier of the physis and invade the joint, resulting in a septic joint (25). (Copyright Kenneth L. Urish.)