What you need to know about osteoarthritis [H&H VIP]

Osteoarthritis is one of the major equine health challenges.

Indiscriminate in nature, this painful joint disorder can affect animals from all disciplines — from the elite racehorse to the treasured pet pony. Its onset can be progressive, as a result of general wear and tear, or may follow injury or trauma. At its worst, the condition can cause early retirement or even necessitate euthanasia.

With careful management, however, it is often possible to maintain your horse’s range of movement, control pain levels and slow the course of joint degeneration.

A long-term issue

Although it can develop at any age, osteoarthritis is most commonly seen in the ageing horse.

One of the major problems is that the disease has a prolonged course. It often starts to develop many years prior to the horse showing any apparent or recognisable signs, such as lameness. There may have been an injury in the horse’s distant past, or some issue with his conformation, which results in a chain of events ultimately leading to osteoarthritis.

Once the disease is clinically apparent, there may be significant — and often irreversible — damage and abnormalities within the affected joint or joints. By the time it becomes obvious that osteoarthritis is causing a problem, diagnosis is usually straightforward.

Prior to this, however, detecting its presence can be challenging. This delay in detection is why osteoarthritis can be difficult to treat and cure.

It would be a major clinical advance if diagnostic tests were developed to identify the condition at an early stage. This would enhance the likelihood of prescribing effective treatment of the disease, and allow appropriate management measures to be implemented to halt its progress.

The performance puzzle

For a horse to appear obviously lame, one leg must be hurting more than another.

Frequently, osteoarthritis simultaneously affects several joints on different legs.

While a horse with low-grade pain in different joints may not show an overt lameness, he may display either a loss of performance or behaviour changes. He may become less forward-going, or his ability to jump or compete may be impaired. This behaviour is often considered “difficult”, and is typically ascribed to general back pain or an attitude problem.

It is important that horses with poor performance or behavioural issues undergo a thorough veterinary orthopaedic examination, as low-grade multi-limb lameness is easily missed.

Modern imaging techniques include digital radiography (X-rays), which can detect subtle lesions, or scanning methods such as computerised tomography (CT) or magnetic resonance imaging (MRI).

These show some promise, but are yet to become practical clinical tools for the very earliest diagnosis, mainly due to their cost and lack of accessibility.

Blood or urine tests have the potential in the future to predict the risk of osteoarthritis by measuring levels of specific proteins. This is an area of research interest but, again, nothing has yet shown enough promise to be turned into a clinically applicable test.

Which treatments work?

There have been no major advances in the last few years in the medication available to treat osteoarthritis in the horse, and there is little in the way of new developments on the horizon.

The mainstays of our basic drug list remain non-steroidal anti-inflammatories (NSAIDs, examples of which are phenylbutazone, flunixin and meloxicam) and drugs such as corticosteroids, hyaluronan (hyaluronic acid) and Adequan® (polysulfated glycosaminoglycan), which are mainly given by injection.

While often very good at treating the signs of equine osteoarthritis, as they can reduce much of the pain associated with the disease, none of these drugs have been shown to have a major effect on returning a diseased joint to normal. They can improve matters, but rarely provide a complete cure.

As a result of the lack of conventional medicines effectively able to treat the condition, other approaches have been developed that are increasingly being used as therapies. These “biological” approaches use either cells or proteins from an individual horse to treat his own affected joints, with the aim of improving joint repair.

A number of treatments with a rational scientific reason as to why they may work are available. However, in contrast with a newly-developed drug, these do not undergo rigorous testing prior to use, and there is currently no clear proof of their efficacy.

These biological therapies are very attractive but can be quite costly and, as yet, lack robust evidence to indicate which cases are most likely to benefit from their use.

Numerous nutritional feed supplements are said to improve the condition, although again there is little scientific evidence to support these claims. But there is considerable anecdotal data to suggest that they may play a supportive role in certain cases.

A diagnosis of osteoarthritis is not necessarily a death sentence for a horse. While he might have to perform at a slightly lower level, he may be able to continue working with careful management.

Ref: Horse & Hound; 5 February 2015