THE BEST DEFENSE against arthritis and degenerative joint disease (DJD) is early detection. Yet, because the early signs of joint disease are subtle, owners must be trained to look for mild joint swelling and heat, rather than lameness.
Early warning signs may include changes in performance, such as a reluctance to change leads, turn barrels, set a steer or take jumps. Although these problems may be related to behavior or training, the possibility of early joint disease should not be overlooked.
While all horses are at risk of developing DJD, several predisposing factors put some horses at greater risk.
If a horse has crooked legs or toes in or out, its joints will have uneven pressure placed on them. (For example, a horse that toes out will have greater pressure placed on the inside of the coffin, pastern, fetlock and knee joints.) This predisposes these joints to soft tissue inflammation and uneven wear of the cartilage, and may eventually lead to the development of DJD.
Older horses are more prone to arthritis. From birth to two years old, a horse's joints manufacture more new cartilage than they wear away. From two to about 15, cartilage replacement roughly equals normal joint cartilage wear. However, from about age 15 and above, cartilage wear begins to outstrip replacement.
As a result, the cartilage wears thin, increasing bone-to-bone concussion and injury to the joint. Tendons and ligaments in older horses also become less elastic, making them susceptible to tears, leading to joint instability and inflammation.
All joints are unique and respond to injury in slightly different ways, making early signs of joint disease difficult to see. Early signs may include heat or swelling of the joint; pain on joint flexion; and various degrees of lameness.
The vet's examination includes observing the horse trot in a straight line and in circles on a hard surface, as well as using nerve and joint blocks (local anesthesia) and X-rays. Other diagnostic tests such as joint fluid analysis, ultrasound and arthroscopy (insertion of a tiny flexible scope to show the inside of the joint) may also be warranted.
Once the affected joint or joints are isolated, additional X-rays will be used to determine the severity of the condition and to rule out other joint problems such as fractures, bone chips or foreign bodies.