Presented by Dr. Lisa Fortier, Cornell University College of Veterinary Medicine, and recorded on Tuesday, October 15th via Zoom.
Intra-articular injections in horses are commonly performed with a multitude of justifications including the perceived source of pain, stiffness, poor performance, routine maintenance, radiographic changes, effusion, or post-operative care. There are numerous products available for injection including corticosteroids, autologous biologics, and polyacrylamide hydrogels, with new products constantly emerging for consideration. To determine which product to use when, it is important to have a current understanding of osteoarthritis (OA).
It has been known for decades that osteoarthritis is an inflammatory disease and therefore mediated by the immune system. OA is not an auto-immune disease like rheumatic arthritis, but there is clear involvement of immune in the initiation and perpetuation of OA. Inflammation in the joint follows that classic cascade of injury/inflammation with primarily neutrophil involvement, followed by cell proliferation and matrix remodeling during tissue formation with an influx of macrophages and monocytes, and finally cell differentiation with tissue remodeling with a predominance of T cells. All of this happens at the level of the synovial membrane where the inflammatory cells originate and infiltrate the joint fluid. Cartilage is an innocent bystander.
Therefore, medications/products for intra-articular use should target immune cells in the joint capsule or synovial fluid. Finally, all phases of inflammation are important; the goal is not to eliminate inflammation, but to ensure that the joint passes through each phase and doesn’t linger in any one phase which would lead to prolonged inflammation, tissue disorganization and scarring with loss of function. Categories of joint medications will be discussed from the lens of OA in an inflammatory disease of the joint capsule.
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