The early signs of osteoarthritis (OA) are synovitis, mild inflammation, pain and lameness associated with it, but there are
little or no abnormalities within the joint. As the problem progresses, more and more changes involve everything around the
joint, and within the joint, degeneration of the cartilage begins to occur, as well as fibrosis of the joint capsule, stiffening
of the joint and continued wear, which eventually results in erosion of the cartilage and exposure of the bone. The conventional
treatment for lameness associated with osteoarthritis, in addition to rest and physical therapy, are non-steroidal anti-inflammatory
drugs (NSAIDs) such as phenylbutazone (bute) to reduce pain and inflammation; intra-articular corticosteroids, with more aggressive
anti-inflammatory effect; as well as and polysulfated glycosaminoglycans (PSGAGs). In recent years, a new therapeutic aid
has been added to the veterinary tool-kit, intra-articular (IA) or intravenous (IV) administration of hyaluronic acid (HA).
Treatment options for osteoarthritis depend on the severity of the condition and the degree of lameness, says Dr. Larry D.
Galuppo, DVM, associate professor and chief of service for equine surgery at the Department of Surgical & Radiological Sciences,
School of Veterinary Medicine at University of California-Davis.
Hyaluronic acid, typically administered intra-articularly, can be used to treat osteoarthritis and lameness depending on
the severity of the condition.
"My initial therapy would be to see how the horse responds to NSAIDs alone. However, understanding that clients are looking
to do whatever they can, I often will recommend oral glucosamine supplements. It is better if you don't have to perform joint
injection immediately, and there is some evidence in people that this therapy gives some response for mild arthritis," he
says. "If it's a mild case of secondary joint disease, I will often recommend the use of NSAIDs along with oral supplementation
of glucosamine. However, this depends on the horse's performance level. There is also the question if we should be using glucosamine-type
supplements as a preventive treatment. Although there is no specific published research studies, there is some anecdotal evidence
that it may be beneficial to help maintain a more normal joint environment in people. If you do not get a response from the
combined therapy of NSAIDs and other joint supplements, then it is often recommended to use intravenous or intra-articular
hyaluronic acid and/or intramuscular PSGAGs.
"Typically for high-motion joints, I'll start with HA injections into the joint, plus or minus the use of IM Adequan(R (PSGAGs) and/or IV Legend(R (HA). As you get a more-severe condition in a high-motion joint, I will combine the HA joint injection with low-dose corticosteroids
as the last option," Galuppo says. "For the low-motion joints (i.e. tarsal joints), most of the time I'll use a medium-dose
of corticosteroids along with NSAIDs. For those joints I don't use intra-articular HA because they have such small joint spaces.
This allows you to maximize the medication to the joint. Arthritis of the low-motion joints can be managed with the addition
of IM (PSGAGs) or IV (HA) as well."
Several products recently have evolved that declare the efficacy of orally administered HA for horses. Intra-articular or
IV injection of HA has considerable research and clinical history, but what of oral HA? The basis for oral HA products tout
the presence of HA as a lubricant naturally found in healthy joints and its benefit as used either IA or IV, but is there
a basis for its use orally?
In some cases of chronic proliferative synovitis, the synovial lining throughout the joint thickens. Typically this causes
resorption of the palmar aspect of the metacarpus immediately proximal to the condyles, termed supracondylar lysis (arrows).