Lameness is something every horse owner dreads and is one of the most common reasons for calling the vet. It can be worrying and frustrating for all involved. In many cases, rest and a short course of anti-inflammatories are enough to settle things down and the horse can go back to work. But what happens when the lameness doesn’t improve? It’s easy to assume that advanced lameness diagnostics and joint treatments are only for top competition horse, but with advances in diagnostic options and medical therapies, this is not always the case. Whether your horse is a high-level eventer or a trusted hacking companion, your vet will be able to work with you to decide on the best course of action for both your horse and you.
Diagnosing the problem
Depending on the circumstances and clinical signs, your vet may recommend further diagnostics such as nerve or joint blocks and imaging such as radiography, ultrasonography or even advanced imaging such as MRI or CT. The aim is to trace the lameness to a specific area and to assess any damage. In this article we will focus on lameness that is restricted to a joint or joints, and the available intraarticular, targeted treatment options. Ensuring that we get an accurate diagnosis will help to guide the treatment plan, which will ultimately improve the chances of success.
The main culprit – Osteoarthritis
One of the most common conditions affecting joints is osteoarthritis. This is a long-term, degenerative condition that causes pain, stiffness and reduced mobility. Signs can be subtle in the early stages, but can progress to more severe lameness, even at rest. In cases of OA, the smooth cartilage in the joint wears down, leading to inflammation and bony changes. The cartilage protects the surfaces of bone in the joint, allowing pain free movement. When the cartilage is worn away, bone meets bone, causing pain and, in turn, chronic changes in the joint associated with new bone formation. While OA can’t be cured, it can often be managed with medications, joint injections, supplements, and careful exercise to help keep your horse comfortable and active. The currently available medications for intra-articular (joint) use act in several different ways, namely, reducing inflammation, protecting cartilage, improving lubrication and, in the case of regenerative therapies, repairing tissue.
Treatment options:
Corticosteroids
Corticosteroids are one of the longest established intra-articular medications for osteoarthritis or joint inflammation. They reduce pain by reducing inflammation, mainly by switching off certain genes that cause inflammation and by blocking the inflammatory pathway, a series of chemical steps that normally leads to swelling and pain. Corticosteroids are commonly used in other conditions, such as allergic airway disease or sweet itch, but in the case of lameness, we tend to administer them directly into the joint, as we can achieve a higher concentration of the drug, right where it is needed with a lower risk of unwanted side effects. Although rare, there is a small risk of laminitis associated with corticosteroid use, particularly in horses who are overweight or suffering from Equine Metabolic Syndrome or Equine Cushing’s disease. By giving the steroids into the joint, we can use much smaller doses than if we gave these drugs intravenously or orally, thus reducing the risk of laminitis.
There is a choice of steroids available, and your vet will decide on the most appropriate one depending on the joint under treatment. Joints are considered as low motion (such as the small, lower hock joints) or high motion (such as the stifle). Certain steroids are better at protecting the cartilage and as a rule are used in high motion joints, whereas those that can damage the cartilage are preferred in lower motion joints, where fusion of the joint may be desired.
It is not possible to predict how well the horse will respond to steroids, however, the vast majority will show clinical improvement, according to one small study approximately 50% of treated horses returned to athletic performance, some for as long as a year, with many more showing good improvement. It is important to remember that some horses will become lame again within a short time. It is possible to repeat the medication, but we cannot give it too frequently.
Hyaluronic acid
Hyaluronic acid (HA) is a natural component of joint fluid and acts as a shock absorber within the joint. In cases of OA, the joint fluid becomes thinner and less effective. HA is available as a joint injection, intravenous medication or oral supplement. Targeted intra-articular medication is usually preferred for single joints or a pair, intravenous administration may be used for more widespread disease. Oral supplements can vary widely in their composition and there is a lack of good quality evidence for their efficacy. Intra-articular HA can help to reduce inflammation, improve the quality of joint fluid and may have a protective effect on cartilage. As with all intra-articular medications there is a very small risk of joint infection, and HA is occasionally associated with a condition called “joint flare” where there is a transient increase in lameness. HA is sometimes used in combination with steroids.
Orthobiologic therapies
More recently, a greater number of orthobiologic therapies (biological treatments for orthopaedic conditions, usually created from the horse’s own blood or cells) have become available. There are several different products available on the equine market, each acting in slightly different ways, but all rely on the processing of the blood to concentrate and extract specific components.
The earliest orthobiologic commonly used in equine practice is PRP, platelet rich plasma. Blood is taken from the horse and processed to concentrate platelets which can then be injected directly into the joint, where they reduce inflammation and encourage healing.
Alpha-2 treatment focuses on the isolation of Alpha-2-Macroglobulin (α2M), a natural protein found in the body that helps to protect joints from damage. It works by trapping and deactivating harmful enzymes called proteases, which accumulate in the joint in cases of OA, and inflammatory chemicals that break down joint cartilage. This helps slow the progression of joint disease.
Another example is APS, (autologous protein solution) which produces a concentrated solution of platelets and anti-inflammatory cytokines from the blood, like PRP. In general, these preparations are more useful in the early stages of disease, or after surgery.
Stem cell therapy
Another potentially useful regenerative treatment is stem cell therapy, which can be derived from the horse’s own stem cells (usually found in bone marrow) or from another horse. These show promising results in tissue regeneration.
Joint fusion injections
As we have discussed, one of the problems with OA is that the lining of the joint capsule becomes less efficient at producing synovial fluid. One new approach is a treatment made of polyacrylamide hydrogel. When injected, it fuses with the lining of the joint, helping to improve function and reduce lameness. In appropriate cases, the reported success rates are very good, even up to 80% of cases showing resolution of lameness after one injection. It is an expensive therapy but does show promising results in selected cases – although there are also some reports of adverse reactions which are being closely monitored by the medicines regulator.
Many of the above therapies are particularly useful in the early stages of the disease. However, in some cases with more advanced pathology, a different approach may be required. In long standing cases of OA in the small joints of the hock, excessive damage to the joint may mean that the best course of action is to allow the joint to fuse. This is only appropriate in very low motion joints and usually limited to the lower hock joints. In these cases, fusion of the joint by injection with ethanol solution may improve the lameness by reducing the movement of the joint.
It is important to note that any case of joint injection carries a small risk of infection of the joint. Your vet will do everything possible to minimise this risk, including sedation where needed and careful preparation of the injection site under aseptic conditions. In some cases, we may also inject an antibiotic at the time, although this is not always necessary.
Successful management still relies on a holistic view. We need to combine accurate diagnostics, appropriate treatment choice, rehabilitation, and preventative care. With the wide array of choices available for targeted, stage appropriate, individual treatments, the future of equine lameness management looks promising for all our horses, from competition animals to companions. If you have any questions, please do not hesitate to ask any of our vets for advice.
