Original Article - theHorse.com
by: Sushil Dulai Wenholz
May 01 2004
If you've been around horses, particularly performance horses, for even a short while, you've probably met someone who's had a horse's joints injected. The procedure--which involves injecting medication directly into the joint to combat such problems as synovitis, osteoarthritis, and arthrosis--is now commonplace. Despite prominent use and continuing research, though, disagreement and debate remain, particularly regarding the effectiveness and safety of the products used and the method of treatment. In this article, we'll outline the primary pro and con points currently being made in regard to joint injections. Certain joint injections, such as nerve blocks, can also be used for diagnostic purposes, but in this article we'll focus on therapeutic uses.
There are three main categories of medication currently used in joint (intra-articular) injections--hyaluronic acid (HA, also known as sodium hyaluronate), polysulfated glycosaminoglycans (PSGAG), and corticosteroids (also called cortisone or steroid). At the most basic level, these medications aim to decrease inflammation in a damaged or diseased joint, explains Elizabeth Davidson, DVM, Dipl. ACVS, an assistant professor of equine sports medicine at the University of Pennsylvania's New Bolton Center.
By reducing inflammation, the medications also relieve heat and pain, allowing the horse to feel and perform better. In addition, since inflammation releases substances that damage cartilage, eliminating the inflammation helps to slow or even stop the cartilage degeneration that's at the heart of many joint diseases.
CORTICOSTEROIDS: THE BIG THREE
There are three primary corticosteroids used for intra-articular injections in horses, each with potent anti-inflammatory properties, but with differing durations of effectiveness. Here's an overview:
Methylprednisolone acetate (Depo-Medrol)--Longest-lasting of the three; typically used in low-motion joints for degenerative joint disease. Colorado State University (CSU) research has shown that this drug does have negative effects on articular cartilage.
Triamcinolone acetate (Vetalog)--Moderate duration of effectiveness; used in high-motion joints at low dosages. Work at the CSU Orthopaedic Research Laboratory showed no negative effects and an increase in the synthesis of essential articular cartilage elements. Triamcinolone acetate might be chondroprotective (protective of the cartilage).
Betamethasone phosphate (Betavet Soluspan, Celestone)--Shortest-acting of the three; used to reduce synovitis and joint inflammation; a CSU study uncovered no deleterious side effects of the drug.--Sushil Dulai Wenholz