Equine OA Synovial Fluid Analysis

SF samples were obtained by arthrocentesis from meta-carpophalangeal (MCP) joints of 8 horses with OA and 8 horses without joint diseases at the Veterinary Teaching Hospital, University of Helsinki. Most of the horses were of warmblood breeds, but 1 Standardbred and 1 Estonian riding pony were also included. Informed owner consent was obtained for each animal, and ethical approval for SF collection and use was provided by the Viikki Campus Research Ethics Committee of the University of Helsinki (Statement 1/2018). The sampling was conducted immediately after medically-induced euthanasia (0.01–0.02 mg/kg detomidine hydrochloride, 0.01–0.02 mg/kg butorphanol tartrate, 0.05–0.1 mg/kg midazolam, 2.2 mg/kg ketamine hydrochloride, T-61 euthanasia solution) due to lameness or non-OA-related reasons including colic, back pain, leg injury, wound, sinusitis, neurological disease, and guttural pouch mycosis. The decisions to euthanize the animals had been made previously without any relation to the research protocol or sampling. The unprocessed SF samples were immediately frozen in liquid nitrogen and stored at –80°C until analysed. MCP OA was diagnosed post-mortem by experienced equine veterinarians based on the presence of wear lines, erosion of articular cartilage, and osteophytes. Joint surfaces were scored according to OA severity as follows: 0 = normal, 1 = mild OA, 2 = moderate OA, and 3 = severe OA [19 (link)]. SF samples were also harvested from CL MCP joints. Only one of them was classified as normal, and the rest had mild-to-moderate OA. In the post-mortem examination of control joints, the MCP joint surfaces either had no macroscopic abnormalities or revealed mild periarticular changes. Regarding medication, 3 control and 2 CL/OA horses had been treated with nonsteroidal anti-inflammatory drugs, 1 control and 1 CL/OA horse had received antibiotics, and 1 CL/OA horse had been treated with antifungals.