Read the following brief case histories to see if you can determine the common cause. We’ll give you a hint the veterinarians didn’t have: The problem is believed to be related to overfeeding very young horses.
A Thoroughbred show hunter was purchased as a green five-year-old. At age six, the owner said he started acting funny and would fall down when being ridden. The horse’s history was sketchy, but the insurance company considered him to be a neurological case.
On arrival to a university clinic, it was learned the horse only did this when schooling in the ring, and it had started just after his training had been expanded to include jumping and dressage. He was OK on a long rein cross-country. He was put on a lunge line at the clinic, and he seemed OK for about five minutes then would sweat, get rough-gaited and throw himself down, quite deliberately.
A three-year-old Standardbred race-trotting gelding had a number of problems that didn’t respond to joint injections. He was knuckled over often behind, interfered, had an oddly shaped hind foot and mild hock filling on the right.
He had been treated for EPM and improved after that but had to have his stifles injected. He was turned out for six weeks. He looked OK on turnout but didn’t run much on his own.
Upon his return to training, he worked short distances with no problem for two weeks, but when the mileage was increased he became rough gaited and stiff behind, started interfering and would break stride. His gaits were disjointed. Back at the barn he would spend some time shifting weight alternately, resting one leg and then resting another.
A four-year-old miniature horse was in training for driving. After about six weeks, he started coming up short on the left front leg. Flexion tests were performed and were negative. A foot bruise was suspected, but soaking and poulticing had no effect on the lameness. He would stand normally when resting and walked normally, but the longer he trotted in harness, the worse he got. After work was stopped, he would sort of drag the leg for a while but would eventually walk out of it.
The answer is below.
Our veterinarians considered tying-up, Lyme disease, and neurological problems in all three. In cases #1 and #2, they considered EPM. It turned out that all three had OCD (osteochondrosis dessicans) lesions.
When we think of OCD, we expect it to present like any other lameness, but it doesn’t always. Symptoms often correlate better with how hard the horse is worked or the type of work than with the animal’s age per se. Because these animals didn’t start any serious work until later in life, the onset of symptoms was delayed
Also, the pattern of a sudden appearance of a rather marked lameness after a certain level of exercise, or only with particular activities, is common with OCD. OCD lesions often involve only discrete areas of the joint surface, so may not cause pain unless the horse performs a certain movement or reaches a level of fatigue that changes the way the joint is loaded. While OCD lesions in very young horses will sometimes heal on their own, the odds of this with mature horses are slim. Surgery is an option if arthroscopy shows a significant cartilage lesion. Otherwise, rest, good nutritional support and use of either injectable or oral joint nutraceuticals can be tried.