corticosteroid joint injections for horses

Veterinarians have relied on intra-articular (IA, administered into the joint) corticosteroids to manage osteoarthritis (OA) in horses for more than 60 years. They have both anti-inflammatory and pain-relieving effects and are fairly inexpensive, making them OA’s current gold standard treatment, said Jonathan D.C. Anderson, BVM&S, Dipl. ACVS, MRCVS, equine surgery specialist at Rainbow Equine Hospital, in North Yorkshire, U.K.

However, their use has been blamed for several complications, including laminitis and septic arthritis. So Anderson explored whether they should remain the gold standard OA treatment during the 2018 British Equine Veterinary Association Congress, held Sept. 12-15, in Birmingham, U.K.

How They’re Used

Intra-articular corticosteroid use in horses with joint issues is prevalent. In one survey, said Anderson:

  • 85% of responding veterinarians used it to manage chronic joint inflammation;
  • 75% used it in horses with radiographic evidence of OA; and
  • 70% used it to treat acute joint pain.

The three most commonly used corticosteroids are triamcinolone acetonide (TA, an intermediate-acting steroid), methylprednisolone acetate (MPA, long-acting), and betamethasone sodium phosphate-betamethasone acetate (BM, intermediate- to long-acting).

Studies have confirmed their efficacy, showing that MPA improved lameness 56-70 days post-administration. Another study showed that TA improved lameness 42 days post-administration, with 50% of horses still sound three months later.

Corticosteroid Concerns

So what are the downsides to their use?

Certain corticosteroids, for all their anti-inflammatory and analgesic effects, can actually have deleterious effects on joint cartilage. Their use “sets into motion a destructive cycle,” said Anderson. He cautioned against using MPA, in particular, because it causes cartilage degradation. On the other hand, TA is classed as chondroprotective (protects the joint), he said, and doesn’t have the same negative effect on cartilage seen with MPA.

Another concern is the purported risk of corticosteroid-induced laminitis (a painful hoof disease in which the laminae attaching the coffin bone to the hoof wall fail). Several studies, however, have proven corticosteroid-induced laminitis to be very rare and not directly attributable to the corticosteroid being used. The horses at most risk are those with metabolic conditions such as equine metabolic syndrome.

“Corticosteroids should be safe if used at appropriate total body doses in horses that are not under metabolic insults,” said Anderson.

Septic arthritis (joint infection) is another potentially serious, albeit uncommon, complication of IA corticosteroid administration. Anderson said corticosteroids can cause bacteria to establish infection in a joint. Inflamed joints are less able to fight off infection from these bacteria than healthy joints, due to their reduced defensive capabilities.

One study suggested that IA corticosteroids increase a horse’s likelihood of catastrophic injury post-treatment, but Anderson said the perceived link might be an indirect effect of increased loading on a pathologic (damaged or diseased) joint.

“While a period of rest is recommended following intra-articular corticosteroid to maximize the therapeutic potency and longevity, exercise itself does not have any harmful effects, nor does it promote increased risk of catastrophic injury in the presence of corticosteroids,” he said.

Lastly, there’s concern over the competitive advantage corticosteroids might give affected athletic horses over healthy ones. For this reason, racing authorities and governing bodies such as the Fédération Équestre Internationale have established guidelines and threshold limits for corticosteroid administration.

The Bottom Line

After reviewing the literature, Anderson concluded that IA corticosteroids should still be our friend.

While we can’t lump all corticosteroids into one category, they “should still be considered a mainstay of treatment of intra-articular inflammation of whatever cause,” he said. “Multiple joints can be injected multiple times within safe limits and sepsis should not be an expected complication if appropriate injection practices are adopted. Not all corticosteroids are the same and TA confers advantages over MPA in most studies. Their effect should be long-lasting and result in good clinical improvement in lameness and effusion (swelling).”