Foal with swollen joints A 16 day old colt had acutely swollen joints and multiple radiographs were made. Two views of the right metacarpophalangeal joint are shown. Studies at 16 days of age Radiographic features Radiographic changes in the right fore fetlock are limited to soft tissue swelling. Additional radiographic studies of other joints failed to identify bony lesions. In the immature patient, the width of the joint spaces appears increased because of the thickness of the radiolucent epiphyseal cartilage. The lucent zones in the distal metacarpal bone and the proximal phalanx are the normal appearance of the cartilaginous physeal growth plates. Swelling persisted and studies were made at 24 days of age Radiographic features Multiple osteolytic foci within the distal epiphysis of the metacarpal bone, proximal epiphysis of the first phalanx, and the proximal sesamoid bones. Soft tissue swelling is prominent but it is difficult to determine radiographically whether the fluid is intracapsular or extracapsular. Radiographic diagnosis Hematogenous osteomyelitis probably associated with a generalized septic condition. The lesions in hematogenous osteomyelitis are typically polyostotic in the metaphyseal/epiphyseal regions with adjacent joint involvement. The lesions in this colt are early without any periosteal response identified. Subchondral bone lysis secondary to suppurative arthritis will appear later. Comments The study demonstrates a failure to identify bony lesions on the first study and shows a remarkable progression of the osteolysis within 8 days. Destructive bone lesions develop much more quickly in the skeletally immature animal. Multiple joints continued to show soft tissue swelling and survey radiographic studies at the later time showed destructive lesions in other bones as well.
