Introduction to Degenerative Joint Disease

Degenerative Joint Disease is a common condition in horses, also commonly known as osteoarthritis. This is a non-inflammatory form of arthritis which frequently occurs in synovial joints. A synovial joint is a moveable joint characterised by a fibrous capsule, articular cartilage, and a synovial fluid-filled cavity. The articular cartilage is hyaline cartilage that lines the epiphysis of the joint end of two bones. Articular cartilage helps to minimise friction while transmitting mechanical forces between two bones and increasing the joint’s contact surface area.  The joint capsule is a fibrous capsule which helps to cover all structures of the joint.

          Knees, hocks, and fetlocks are commonly affected by osteoarthritis. The condition can occur within a single joint or within multiple joints. Depending on the location, it can be either symptomatic or asymptomatic. The condition is common among horses of all ages, but it occurs most frequently in adult sporting horses. The causative agent for degenerative joint disease is still unknown, however stress occurring in the joints due to heavy workload, poor management, genetic problems, and poor practice methods can cause a predisposition to this condition.
        Degenerative changes in the articular cartilage are the leading cause of osteoarthritis. Horses which are able to carry heavy loads have thick articular cartilage. As the animal ages, the thickness of articular cartilage gradually decreases, and eventually the animal’s weight-bearing capacity also decreases.

Bone damage in the joints causes mild changes in the smooth surface of the articular cartilage in the epiphysis of bones. This leads to degenerative changes in articular cartilage, which is the major predisposing factor for degenerative joint disease.

Some breeds of horses are more susceptible to osteoarthritis, and have certain sites that are more prone to this condition. Osteoarthritis in the hock joint, for instance, is common among cutting horses, and osteoarthritis in the knee joint is common among racehorses.

What are the symptoms? How do I diagnose my horse’s pain?

As a horse owner, you should always identify symptoms of any condition as soon as possible in order to prevent these conditions from becoming more severe. If you fail to identify the early clinical signs of degenerative joint disease, the results can be profound. If you have identified early signs of osteoarthritis, you should commence treatment as soon as possible. It is always advisable to contact your veterinarian if symptoms appear.

Osteoarthritis is a progressive chronic disease, with clinical signs including lameness, stiffness, swelling of the affected area and pain. The most common clinical sign in affected horses is lameness. You can read our lameness article for a more detailed look at this condition and its symptoms. To give a basic run-down of the condition, lameness is defined as an abnormal gait or lack of capability to maintain a normal gait. Lameness is not a disease in itself, but is a clinical symptom of other conditions. Lameness usually results in pain and mechanical restriction of the horse’s limb. 

Another clinical symptom in horses suffering from osteoarthritis is stiffness. Animals suffering from this symptom are often reluctant to move and present restrictions in the motion of the affected limbs.
         Accumulation of fluid in the joint capsule causes swelling to the affected area. Changes in colour and increased temperature around the joint can also be indicators of degenerative joint disease.

When osteoarthritis is chronic, the articular cartilage is completely worn out. This means that there will be a lack of cartilage covering the edges of the two bones in the joint around the epiphysis. Free margins of the bones directly touch one other when the animal makes any movements, causing severe pain and discomfort to the animal, resulting in stiffness, lameness and restriction of movement.  If you attempt to exercise an animal suffering from this condition, it will likely display aggressive behaviours. It is important to identify the condition early and remove the animal from work to give it some relief.

Horses affected by this condition may also feel stress and may reduce their feed intake. This can result in the animal suffering from emaciation, weight loss, and lack of power and energy in performance. If you think your horse may be suffering from osteoarthritis, take immediate action. Contact your veterinarian, who will perform further diagnostic methods and start treatments. If you fail to take immediate action, your horse’s performance may be affected permanently. 

A number of confirmatory diagnostic methods such as X-rays, arthroscopy, nuclear scintigraphy, and serum biochemical tests can help to confirm if your animal is suffering from osteoarthritis. Arthroscopy is a new and very sensitive technique which identifies defects in the articular cartilages. Using this method, a clinician can obtain a clear image of the inside of a joint. This helps to diagnose osteoarthritis in its early stages. Although X-ray is commonly used as a confirmatory method, it is not able to identify changes in articular cartilage. It can, however, identify the narrowing of the joint space caused by the loss of articular cartilage.
      Nuclear scintigraphy is another very sensitive test. This is a method of bone scanning from which inflammatory joints can be identified. Serum biochemical testing is a biological technique which can also be used for the early diagnosis of joint disease. A biomarker is used as an indicator, which can give the clinician an idea of the metabolic processes inside a horse’s body. Changes in the specific serum enzymes (biomarkers) in the blood can indicate that a joint disease is present.

How to look after a horse with DJD?

Above all, it is important not to panic if your horse is diagnosed with osteoarthritis.  By managing the condition with great care, you can help to reduce the spread of disease within the horse and keep the animal comfortable. Do not use the affected animal for heavy workouts. Mild exercises, however, are recommended to maintain activity in the joints. Affected horses can tend to become overweight due to a lack of exercise, and it is important to do your best to avoid this happening. Providing sufficient shelter and good bedding will help the animal lie down and get up easily.

        Sadly, degenerative joint disease is incurable. Although it is not possible to cure the disease, it is possible to reduce its spreading, reduce the animal’s pain, and help to allow the articular cartilages to regrow. In order to achieve all of the above, try the following:

Trim the horse’s hooves properly to ensure its balance. Shoes should be fitted using proper methods as improper shoeing and unbalanced hooves predispose the animal to degenerative joint disease and make the condition more painful and severe.

Some of the easiest treatments to carry out are hot and cold therapies. Hot therapy can reduce pain and stiffness by increasing blood flow. This helps to relax the ligaments and tendons. Cold therapy helps to reduce the swelling and pain around the joint.

A healthy balanced diet can provide essential nutrients for joint repair. Some nutrients in the diet can even help to relieve pain. Proper nutrition will prevent your horse from becoming overweight, a condition which can incur further issues and symptoms.

Conclusion 

You should now have a good knowledge of degenerative joint disease and its clinical signs, diagnostic methods, prevention methods, and treatment! To summarise, it is a degenerative disease affecting the articular cartilage. Also known as osteoarthritis, it is a complex condition which can result in gait abnormalities and pain. This can lead to a significant decrease in performance.  Do consider preventative action, and keep an eye out for any symptoms in your horse so that you can treat the disease promptly and effectively!