Osteoarthritis, i.e. degenerative joint disease (DJD), is one of the main causes of lameness in horses and it starts when cartilage in joints is damaged producing inflammation and pain. Usually therapy involves intra-articular medications such as corticosteroids and/or hyaluronic acid, rest, NSAIDS such as ‘bute’, polysulphated glycosaminoglycan (PSGAG) such as “Adequan”, pentosan polysulphate such as “Cartrophen”, and oral supplements containing glucosamine and/or chondroitin sulphate.
More recently a treatment called IRAP (Interleukin-1 (IL-1) Receptor Antagonist Protein) has been developed. This uses the horse’s own serum to combat osteoarthritis in the joint. IL-1 is a cytokine secreted by cells of the immune system to attack infections and damaged or dying cells. Although this is an important part of the inflammatory response, it can be detrimental to joints by accelerating deterioration of the cartilage. IRAP works by blocking IL-1 from binding to tissues and as a result preventing the damage to the cartilage. Therefore the reason IRAP is exciting is its potential long-term effect on cartilage i.e. preventing an injured joint becoming an arthritic joint.
The procedure starts with sterile collection of blood into a syringe with special glass beads that stimulate production of IL-1. After incubation and centrifuging the IRAP rich serum is injected into the affected joint in a sterile manner. Usually IRAP treatments are given on three occasions at two week intervals. Case selection is very important and IRAP is of most benefit in joint disease where no x-ray change can be seen but pain has been localised exclusively to the joint. In these cases we have found IRAP to be remarkably effective with horses returning to normal work. In addition we have also seen benefits in its use where there is a damaged ligament associated with a joint for example with coffin joint collateral ligament injuries. It is however no substitute for surgery where fragments must be taken out, and there are also limitations in its use for the later stages of joint disease.