DEGENERATIVE CHANGES AND ARTHRITIS

Arthritis literally means ‘inflammation of the joint’. Most horses, especially older horses, will have some degree of arthritis present in their joints. Arthritis is very difficult to avoid, but preventative treatments can be of benefit and arthritis can be successfully managed once it has arisen, to slow its progressive course.

About joints

Most joints are made up of at least two bones, which are protected by cartilage lubricated by synovial fluid and stabilised by tendons and ligaments. Healthy cartilage in the joint provides a smooth, slippery surface that allows free movement and contributes to the shock-absorbing properties of the joint.

Everyday wear and tear can cause an enormous amount of stress and damage to the joints of a horse. As the demand on the horse’s athletic ability increases, so the risk of damage to the horse’s joints also increases.

About arthritis

Joint problems can be caused by injury, but the most common cause is in fact arthritis. 70% of all lameness seen in horses is due to arthritis. Arthritis is a painful, progressive and permanent long-term deterioration of the cartilage surrounding the joints. Hence, it is also referred to as degenerative joint disease (DJD).

As arthritis becomes established, the cartilage lining the joint becomes increasingly damaged, which disrupts the initially smooth and slippery surface lining the joint. This causes a decrease in the horse’s range of motion. Ultimately this cartilage will be worn away to the point where the bone beneath the cartilage starts to become exposed and then damaged as well. In response to this, new bone often grows in the affected limbs, as bone is generated more easily than cartilage. The bone is therefore used to replace the cartilage, yet it does not have the same slippery, smooth properties as the cartilage it is replacing. In more advanced cases, small bone growths called osteophytes start to grow out from the bones in the joints that have been damaged. Small cysts may also start to be seen within the bone. These can be seen on x-ray examination.

Arthritis is the most common cause of lameness in sport horses. The degree of lameness varies depending on the stage to which the disease has progressed. Arthritis tends to worsen with age, as the body’s natural ability to repair itself slows down.

Types of arthritis

The most common type of arthritis is osteoarthritis, which is a degenerative joint disease caused by wear and tear of the joints. This is the type that this article will focus on. However, it must also be mentioned that some cases of arthritis do occur due to infection or due to trauma.

Septic arthritis is where there is an infection of the joint. This is a particularly devastating form of arthritis, as it quickly destroys the structures of the joint. The horse will suddenly develop severe lameness, as the pain that septic arthritis causes is enormous. Antibiotics are used to treat the infection, but often the joint is severely damaged and the career of the horse is commonly ended.

Trauma can also damage a joint and leave it with arthritis. The type of injury determines the severity of the lasting joint damage.

Symptoms of arthritis

• Stiffness or lameness that commonly improves after warming up
• Slow or stiff movements after a period of rest or in cold weather
• Shortened strides
• Uneven gaits
• Hollowing of the back and lifting of the head
• Puffiness around the joint
• Warmth around the joint
• Pain on palpation of the joint
• Difficulty lying down or getting back up
• Behaviour changes such as bucking, rearing or kicking
• Reluctance to pick up or change canter leads
• Reluctance to jump with stopping or running out of jumps
• Reluctance to perform everyday activities
• Loss of muscle mass

Horses with osteoarthritis will commonly initially show signs of stiffness. The stiffness gradually gets worse, until the horse is looking uneven and ultimately unsound. Generally, more joints will become involved as the process progresses.

Affected joints

Equine arthritis can actually affect any joint in the body. The most commonly affected joints, however, are the weight-bearing joints or the limbs and hooves, as these undergo both stress and compression forces from the weight they carry. For example:

• Hocks – arthritis in the hocks is commonly referred to as bone spavin
• Fetlocks
• Pastern and coffin joints, where it is often referred to as ringbone
• Stifle joints (less common here)

The other frequently affected joints are those of the back and neck, although this is less common than problems in the weight-bearing joints.

Horses with poor conformation or poor balancing of their feet put extra stress on joints, which can lead to earlier onset arthritis in these joints.

Diagnosis

Diagnosis of osteoarthritis is usually relatively straightforward with vets generally having a good idea what they are dealing with just from the history and the physical examination. However, they can only conclusively make the diagnosis from x-rays showing the classical changes in the joint (the bone cysts, the osteophytes, the chips, the irregularity of the surface of the joint and the narrowing of the joint space).

Treatment

Although there is no cure for arthritis, steps can be taken to reduce the risk of developing arthritis by adding a joint supplement to the horse’s diet. For horses with existing joint problems, the right combination of active ingredients not only will slow down the progression of the disease, but has been shown to rebuild and regenerate damaged cartilage in the joint and help with managing pain and inflammation.

Sometimes joint injections with hyaluronic acid, glucosamine or corticosteroids may be advisable. Stem cell therapy is also available for arthritis, but this is very costly.

It is likely that ultimately the workload of the horse will gradually need to decrease to avoid putting excessive stress on the affected joints. This may mean an end to the horse’s competitive career, but light exercise should always be maintained to keep the joints from becoming stiff and seized up. A properly balanced trim of the foot is essential to reduce the pressure on the affected joints.

Preventative strategies

To be clear, osteoarthritis is due to the wear and tear of joints, but this is not a reason to avoid exercising your horse. Exercise is very beneficial to all of the musculoskeletal structures within the horse’s body, and even the cartilage in joints responds positively to the stimulation of exercise. Caring for your horse’s joints is just a case of ensuring that you ride regularly but avoid fatigue and total overload. It means that you need to jump on soft surfaces, and not to jump in every single training session with the horse. It means that your horse needs a fitness programme that builds him up gradually to the point that he is ready to perform the movements and tasks that you require of him. In essence, a well-structured and thought-out training programme for a horse can be beneficial for the musculoskeletal system as a whole, but also the joints themselves. This is the best way to prevent arthritic changes.

Weight management is also essential in horses to reduce the risk and progression of arthritis. Extra weight puts additional pressure on the joints, which increases the chance of arthritis developing.

Similarly, a horse must have a properly balanced trim or shoeing to stand the best chance of delaying the onset of arthritis. Any imbalance in the feet will affect not only the joints in the feet but also the joints higher up. This imbalance can lead to uneven forces acting upon and within a joint, which ultimately results in an increased likelihood of arthritis.

As mentioned, joint supplements are another option for horses and many riders and vets swear by them. It is worth doing your research into these supplements and choosing one with ingredients that have proven efficacy in horses.

NOTE: If your horse becomes unsound suddenly you need to call your vet immediately and not simply attribute the change to arthritis. Osteoarthritis has a much more gradual onset and tends not to get suddenly worse. Septic arthritis on the other hand typically develops suddenly and is a veterinary emergency.