Sodium hyaluronate (hyaluronate sodium) is a mucopolysaccharide that is useful in the treatment of synovitis not associated with severe degenerative joint disease. It may be helpful to treat secondary synovitis in conditions where full thickness cartilage loss exists.3 Sodium hyaluronate is found normally in the connective tissues and synovial fluids of equines and many other animals. Because this compound is normally found in the horse's body, it does not create immune reaction when horses are treated with it.Sodium hyaluronate can help in maintaining the joint health of horses. It also acts to inhibit inflammatory responses and improves the lubrication of the joint fluid. It is used both intravenously (injection directly into a vein) and intraarticularly (injection directly into a joint space).2,3 most sodium hyaluronate products are approved for use in the fetlock and carpal (knee) joints, though they are also used in other joints (extra-label). Clinical trials have shown 90% or higher positive responses in horses treated with sodium hyaluronate, either intravenously or intra-articularly, for joint arthritis.Some patients may develop local reactions manifested by heat, swelling, and/or effusion. Effects generally subside within 24-48 hours; some animals may require up to 96 hours for resolution. No treatment for this effect is recommended. Sodium hyaluronate is not recommended for horses with an infectious cause of joint inflammation, nor should it be injected into a joint with an associated fracture.2