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to yearling age. More commonly, the signs of abnormality are less pronounced, and the horses will show clinical signs of recurrent mild to moderate lameness associated with waxing/wan- ing joint distension when they are first intro- duced to training or vigorous athletic activity.” The joints are stressed more at this time, causing them to be symptomatic.
This manifestation can appear at dif-
ferent ages, depending on breed. “In racing Standardbreds and Thoroughbreds, this may be the latter part of their yearling year when they start training,” he says. “Warmbloods may not show until 3 to 5 years old because they get started in training later in life than racehorses. This also depends on whether they are jumpers or dressage horses. In Quarter Horses, it occurs whenever they first go into training, in their various careers.
“The two main signs to look for are big joints (excess fluid production in joints, caused by irritation from the fragment) and lameness,” Schramme continues. “When you rest these young horses, they get better; when you push them harder, they get worse. There’s also an interesting correlation between the size of the lesion and the age at which joint distention and lameness appear. Generally speaking, the bigger the fragment, the earlier the signs will appear.
“These are separating fragments, at joint sur- faces. The term osteochondritis dissecans means a dissecting lesion--separating away. There is wide variation as to how loose the fragments are. During surgical removal, some are still so firmly attached that you must chisel them off. Others are barely hanging on with a piece of connec- tive tissue, and others will actually be loose and floating around in the joint, creating what we call joint mice. If these catch in the joint, they are quite painful and can cause significant dam- age to the surrounding cartilage. Lameness will be consistently present rather than waxing and waning,” he explains.
Treatment for OCD can vary. “Recommendations for treatment differ from joint to joint, and also according to the purpose of the horse and its projected career. There is definitely an indication that the faster the horse is expected to go (such as a racehorse), the more this disease will be a career-limiting problem. There are different rules of thumb for each joint. In the hock, for example, the average general-purpose horse or trail riding horse can happily live with the presence of fragments
and some joint distension without having problems. But the faster a horse has to go, such as racehorses, or any horse that must gallop
at high speed, the more likely the condition will interfere with performance.” A racehorse may not be willing to run to full potential because of soreness and lameness caused by joint inflammation, whereas a general-purpose
Wobbler disease is caused when growth plates of vertebrae in the neck become misshapen because growing cartilage does not progress into normal bone formation.
riding horse may never have to go fast enough for long enough to be bothered by it.
Today many people have pre-purchase radiographs taken before buying a horse. Regardless of what the purpose of the horse will be, when these fragments are seen on radio- graphs, veterinarians usually recommend that they are removed surgically--especially if the radiographs are taken for the seller, rather than the purchaser. If someone is trying to sell a horse and it has OCD fragments in a joint, the horse will be harder to sell, or may have to be sold at a reduced price.
These fragments can be removed relatively easily through arthroscopic surgery. This is a very benign procedure that frequently leaves no significant scar. You can hardly tell the horse has had fragments removed. “It’s just two little stabs (one to put the arthroscope in and one to pull the fragment out) and two sutures,” explains Schramme. “After this surgery there is a very good chance the horse will be sound, and also
a very good chance that the joint swelling will never reappear.
“We need to remember that there is a win- dow of opportunity in which a younger horse may have a chance to heal these lesions without surgical intervention,” he says. “As surgeons, we try to put off doing surgery on the youngest
horses until they are about a year old because in some individuals these lesions will heal on their own. Admittedly, I have to say that only the smaller lesions tend to repair themselves. The larger ones are less likely to resolve spontane- ously, but we try to give the smaller lesions in the youngest horses a chance to self-repair.”
SUB-CHONDRAL BONE CYSTS
During the cartilage maturation process in young, growing horses-(in which cartilage at the end of the long bones turns into bone)-there may be some retention of thick cartilage which degenerates and forms a hollow spot (cyst). The bone around it has formed normally, but there is a weak or empty spot within it just below the joint surface.
“This part of the bone never ossifies properly and therefore a cyst forms,” says Schramme. “This is seen in many different joints, but cysts are much more rare than dissecting lesions and most commonly seen in the stifle. Cysts can also be seen, to some extent, in other joints such as the fetlock or shoulder. In Quarter Horses, the pastern joint seems to be a common site. You tend to see lameness or joint distension caused by these bone cysts in young horses from 6 months to 3 years old, when they are first intro- duced into training.”
EQUINE HEALTH
During the cartilage maturation process in young, growing horses-(in which cartilage at the end of the long bones turns into bone)-there may be some retention of thick cartilage which degenerates and forms a hollow spot (cyst).
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