Horse breeders have long known that problems can develop in the bones of young horses as they grow. The term developmental orthopedic disease (DOD) was coined in 1986 to encompass all orthopedic problems seen in the growing foal and has become a generally accepted term, says Wayne McIlwraith, BVSc, PhD, DSc, FRCVS, Dipl. ACVS, director of orthopedic research at Colorado State University. Developmental orthopedic disease is a blanket term for various manifestations of limb abnormalities in young horses, but they all don’t have the same cause(s), and they might involve joints or growth plates rather than just bone, notes McIlwraith.

In this article, we will discuss some of the common developmental ailments of young horses, including osteochondrosis, bone cysts, and physitis. We will explain what these conditions are, what is thought to cause them, and what to do about them.

There are basically four causes of osteochondrosis, and affected horses usually have a combination of these:

1. Genetic predisposition;

2. Rapid growth (which includes growth spurts that can occur when foals "catch up" after the stress of weaning, illness, or some other factor when growth was temporarily slowed);

3. Nutrition (high energy intake, mineral shortage, or imbalances); and

4. Trauma and the role of exercise and overload.

"The latest information is that it’s better to provide foals with free turnout than to confine them completely or to confine them and give them short bouts of high-speed activity," says Michael Schramme, DrMedVet, CertEO, PhD, Dipl. ECVS, clinical associate professor of equine surgery at