Use of corticosteroids in joint disease

Summary

The use of intra-articular corticosteroids is a common therapeutic in equine practice for management of cases of synovitis and osteoarthritis, and their use is extremely common in sports and competitive horses. However, despite their widespread adoption in equine practice, the use of corticosteroids is not without controversy. Administration of corticosteroids can lead to rare, but serious, complications. They may also be used to simply mask pain due to significant pathological issues, which following drug administration could progress onto catastrophic injury. Despite these issues, there is a strong clinical acceptance that intra-articular administrations of corticosteroids are extremely useful therapeutics in the treatment of joint inflammation and pain.

Keywords : Joint, corticosteroid, osteoarthritis

Abstract

The action of corticosteroids is exerted through the interaction with steroid-specific receptors in the cytoplasm of steroid-responsive tissues. This interaction results in the altered transcription of genes leading to a wide variety of anti-inflammatory effects as well as other effects on the biology of articular cells that are of variable benefit. Corticosteroids are able to suppress inflammation at virtually all levels. The humeral affects of corticosteroids are due to the inhibition of phospholipase A and the decrease in production of pro-inflammatory mediators by both the cyclooxygenase and lipoxygenase pathways. They also inhibit many of the other inflammatory effects such as capillary dilation, migration of inflammatory cells and the production and release of degradative enzymes.

The use of corticosteroids as a treatment of joint disease has been controversial due to concerns of side effects associated with accelerated joint degeneration due to possible negative effects on cartilage matrix. However, experimental data and their widespread clinical use over the last few decades now indicate that in many instances judicious use of intra-articular corticosteroids can be beneficial. Side effects of their use include iatrogenic synovial sepsis and laminitis, which both can be extremely serious and possibly fatal. To decrease the possibility of sepsis, some veterinarians inject an intra-articular antibiotic, for instance gentamicin or amikacin, at the time of corticosteroids administration. This is something I have never done and advise it is probably unnecessary in most instances.  No scientific studies have proven a causal link between the use of intra-articular corticosteroids and laminitis although there have been anecdotal reports to the contrary. Unsubstantiated reports suggest a narrower therapeutic index with triamcinolone with respect to laminitis as a secondary complication. Certainly in the UK, it is probably now normal veterinary practice to warn an owner of the risk of corticosteroid induced laminitis when treating a horse with corticosteroids. The risk is probably greatest in heavyweight or overweight horses which may be predisposed to equine metabolic syndrome. Furthermore, unsurprisingly, the risk is probably greatest in horses which are receiving high doses of corticosteroid in which multiple joints are being treated.

There are numerous corticosteroids that can be used as intra-articular therapy. Betamethasone is rarely used for this purpose in the UK although it has been argued that it may be an appropriate drug due to its short duration of action. Triamcinolone acetonide is a commonly used moderate to long acting corticosteroid. Experimental data has indicated that in models of joint disease this corticosteroid both improved lameness and improved articular cartilage morphological parameters in comparison to control animals in a relatively aggressive form of OA. This particularly study concluded that intra-articular administration of triamcinolone acetonide improved lameness, had some chondroprotective effects and no substantial detrimental effect on the joint. This corticosteroid is widely used in the therapy of joint disease, especially in the management of diseases affecting high motion joints, such as the carpus, fetlock and distal interphalangeal joints. We would normally advise such treatment as a one off therapy in most cases, and as always with such treatments it is important to treat the primary cause of the joint disease. Probably the most common indication for corticosteroids is in the therapy of synovitis, especially in competition horses where there is a rapid requirement for resolution of symptoms and rapid return to training.

Methylprednisolone acetate is commonly used in the UK and is longer acting compared to triamcinolone. Clinically, this drug has been shown to improve the microscopic appearance of the synovial membrane and the synovial fluid parameters. However, in experimental models of OA clinical improvement is not as marked and it may have a more detrimental effect on the articular cartilage. As such we predominantly use this drug as a treatment for OA of low-motion joints such as the small tarsal joints and the proximal interphalangeal joints. In some cases, treatment would be repeated in 4-8 weeks if only partial response is observed, or even several months later if lameness returns.

The decision of when to return horses to exercise following corticosteroid therapy is currently unclear with some clinicians recommending a conservative approach as these drugs can affect cartilage metabolism in both normal and abnormal joints for periods of between 4 and 8 weeks. Thus, a total period of rest and slow return to exercise has been recommended for approximately 14 days, although others have returned horses more quickly to work without detrimental effects. Frequently owner/trainer demands require a much more rapid return to work than that is probably most beneficial for the longevity of the horse. In most be remembered that many racing and competition jurisdictions consider intra-articular corticosteroids as banned substances in competition. The situation is complicated as the drug detection time and drug withdrawal time for corticosteroids (such as triamcinolone) is undoubtedly variable and often longer than the commonly stated period of time of 10 days historically used by veterinarians. Many racing jurisdictions are putting in effort into testing to identify medicated horses.

The safety of corticosteroids and their role in induction of catastrophic injury has been the subject of considerable scrutiny in recent years. A recent retrospective cohort study identified an increased risk of musculoskeletal injury following corticosteroid injection, which lasted for 49 days subsequent to injection. The risk of injury increased with further corticosteroid treatment.

In recent years there has been a demand by many owners and trainers for routine or prophylactic injection of corticosteroids into joints in apparently sound horses. The rationale for this is uncertain, and it is hard to support such practice where corticosteroids may have both detrimental as well as positive actions. Currently there is no evidence that such practice has any effect on improving future soundness or working longevity in horses.