Diagnosis This foal has infectious arthritis that is localized in the right rear fetlock joint. The likely route of infection considering the young age of the foal is hematogenous spread via the navel. An alternative cause to the infection could be that the foal may have sustained a penetrating injury that is clinically indetectable Đleading to sepsis. Sepsis must have preceeded the joint infection because the growth plate of the third metatarsal shows characteristic radiographic changes. The bacteria gbecome trapped in the small diameter capillaries that feed the growth plate. The infection spread from this location locally into the fetlock joint. The joint tap showed Klebsiella and increased protein (from the bacteria and wbcs) in the joint fluid, which supports the diagnosis of joint infection. The increased fluid and lytic bone changes associated with the infection account for the sensitivity and pain associated with that joint. Chemotactic factors released from the bacteria cause increased white cell migration to the site of infection. Prognosis The prognosis for joint sepsis is better for foals with a single joint infection than for adults. However, involvement of bone and increased duration of infection reduce the chances of favorable outcome. Overall, the prognosis is guarded.