Osteochondral Fragmentation in the Synovial Pad of the Fetlock in Warmblood Horses

To determine clinical and arthroscopic characteristics associated with fragments in the synovial pad of the fetlock and to characterize their morphology. Retrospective study. Warmblood horses (n=104) with fragment(s) in the synovial pad. Signalment and results of radiographic and clinical examination were collected before surgery. After arthroscopic fragment removal and joint evaluation for synovial and/or cartilage abnormalities, fragments were measured, and evaluated by histopathology. Synovial pad fragments (n=142) were removed from 127 fetlocks. Two older horses had lameness. During arthroscopy, abnormalities were observed in 40 joints (31.5%) and multivariate logistic regression analysis showed a significant correlation between the observed arthroscopic abnormalities and the presence of large fragments (P=.016). Fragments were osteochondral bodies completely surrounded by fibrous tissue. At the edges of the hyaline cartilage cap an underlying fibrous structure was obvious in the extracellular matrix giving it a reactive pattern. Although the impact on lameness was minimal, there was a significant correlation between arthroscopic abnormalities and presence of large synovial pad fragments. On histopathology, these osteochondral fragments are embedded in fibrous tissue and show a reactive pattern. They are not a manifestation of any well-described joint pathology. Large synovial pad fragments in Warmblood horses can be associated with synovial and cartilage abnormalities, but further studies are warranted to determine their origin and clinical importance.