Degenerative Changes in MCP/MTP Joints of Working Horses Without Lameness: Integrating CT-Based Assessment and Synovial Fluid Biomarkers

Working horses often develop distinct patterns of joint degeneration, yet research in this population remains limited. This study aimed to characterize degenerative changes in the metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joints of Serbian Mountain Horses using computed tomography (CT) and to explore their associations with synovial fluid (SF) biomarkers. A cross-sectional analysis was conducted on 32 MCP/MTP joints from eight clinically sound horses. Postmortem, joints underwent CT imaging, and SF samples were analyzed for viscosity, protein content, total nucleated cell count (TNCC), and oxidative stress biomarkers, along with matrix metalloproteinase (MMP) activity. Subchondral sclerosis was present in all joints, occurring more frequently in horses aged less than nine years. Osteophytosis was observed in two-thirds of joints, and its severity correlated significantly with body weight. Both changes were localized on the medial and lateral condyles and were associated with elevated TNCC, while osteophytosis was linked to increased total oxidant status and oxidative stress index. Relatively low levels of β-hydroxybutyrate appear as a main interactive factor for both changes. No associations were found with MMP activity. These findings indicate that clinically sound working horses commonly exhibit early degenerative joint changes accompanied by mild increases in TNCC and oxidative stress biomarkers.