Osteoarthritis

What is osteoarthritis?

Osteoarthritis (OA), formerly known as degenerative joint disease, is the most common joint problem in horses, accounting for more than 60% of equine lameness. The term “arthritis” refers to joint inflammation, and there are many types and causes in horses. Osteoarthritis can occur in any synovial joint. It is a degeneration of the cartilage that can be precipitated by factors including repetitive trauma, historical fractures or other injuries, and/or poor conformation that can increase stress on joints. High-speed training is also a risk factor. Osteoarthritis gets progressively worse with age, but can affect horses of any age and breed, with males and females equally affected.

What are the clinical signs of osteoarthritis?

The predominant clinical sign of osteoarthritis in horses is lameness, which may be intermittent but recurrent with sudden onset or slowly progressive. Affected horses may exhibit reduced range of motion in one or more joints, which often becomes worse over time. Additional clinical signs can include swelling, heat, pain on manipulation of the affected joint. Some horses may be stiff when they come out of their stalls or begin working, but often look more comfortable after warming up.

How is osteoarthritis diagnosed?

Osteoarthritis is most commonly diagnosed based on lameness examination and x-rays, but in certain cases advanced imaging (such as CT, MRI, or PET), and diagnostic arthroscopy (a minimally invasive procedure that uses a small camera to visualize, diagnose, and treat joint problems). Diagnostic analgesia (“blocking”) can be used to identify the source of pain. Imaging may show narrowed joint space, bony outgrowths, and excess joint fluid.

How is osteoarthritis treated?

A variety of treatment options are available, but there is no single standard treatment or known cure for OA. Most treatments for osteoarthritis in horses are aimed at reducing pain and slowing the disease process. These include non-steroidal anti-inflammatories (NSAIDs), nutraceuticals, and intra-articular (IA) medications including corticosteroids, hyaluronic acid (HA), platelet rich plasma (PRP), and interleukin-1 receptor agonist protein (IRAP). Physical therapy, including underwater treadmill therapy, may be recommended. Depending on which joint(s) are involved, surgical fusion (arthrodesis) may be performed. Management of horses with OA should include specialized trimming/shoeing, weight loss for overweight horses, and appropriate exercise (duration and intensity) as determined by a veterinarian. It is important to note that pain management does not treat the underlying disease process.

What is the prognosis for osteoarthritis?

Since there are so many factors involved, the prognosis for affected horses can be variable depending on the severity of the disease, single or multiple joint involvement, whether high or low motion joints are involved, historical and intended horse use, as well as clinical signs of OA and how long they have been present.

How can osteoarthritis be prevented?

Development of OA is most often due to normal “wear and tear” over time but can develop following a single traumatic event. Horses with a traumatic joint injury can develop secondary OA. Prevention is key, and methods to promote joint health include keeping horses at healthy weights (BCS of 4-5 out of 9), avoiding repeated maximal exercise (especially in young horses), ensuring exercise is of appropriate duration and intensity, and providing adequate turnout and appropriate footing.  It is also important to diagnose OA early and limit inflammation to prevent further damage.

*This article may not be reproduced without the written consent of the UC Davis Center for Equine Health. Please email requests to cehadmin@ucdavis.edu.