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Dr Jennifer Stewart BVSc BSc PhD Equine Veterinarian, CEO Jenquine and Consultant Nutritionist Equine Clinical Nutrition
Although affecting 20-25% of all 3-12 month old foals, the term developmental orthopedic disease (DOD), was coined in 1986 by the American Quarter Horse Association to describe skeletal problems in growing horses - limb deformities, bone cysts, contracted tendons, club feet, joint enlargements, wobblers, osteochondritis dessicans (OCD) and physitis (Figures 1 and 2). Osteochondritis dissecans (OCD) is weak, malformed cartilage that results in flaps of cartilage and bone that either remain attached or break off and float around the joint. It is linked to rapid growth, large body size, high energy diets, mineral imbalances, insulin and thyroid fluxes. Figure 1. OCD lesion Most lesions are not detectable (even with Xrays) until the damage causes lameness or joint swelling. Signs of stifle DOD are commonly found in horses from 6m-2yo; hocks 6m-3yo and shoulder OCD or bone cysts 1218mo. However, the disease is present long before signs appear and begins during periods of vulnerabilty.
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Physitis is swelling around the growth plates due to overload on the bones, weakened cartilage. It is associated with excess energy, high body weight, conformational defects, calcium deficiency and excess exercise. It often occurs in well-grown, fast-growing, heavy-topped foals during the summer when the ground is dry and hard. It is characterized by flaring of the growth plate, giving a typical “boxy” appearance to the affected joints. Figure 2. Physitis The period from 3 months before birth to 5 months of age is one of turbulent change for the musculo-skeletal system. Many dynamic remodelling processes take place, which profoundly influence the strength and integrity of bones and joints. From 5 to 11 months, growth and development continue at a slower rate and the final constitution of joint cartilage has been formed by 5 months of age. Because these processes are only active during the first year of life, DOD lesions only develop during this period – even though they may not show up for months or years later.
SPRING 2023
