Juvenile Osteochondral Conditions

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Young, growing horses are often prone to developmental orthopedic disease (DOD). One primary manifestation of this syndrome is that of osteochondral (OC) lesions. A recent paper by Jean-Marie Denoix, DVM, PhD; Leo B. Jeffcott, BVetMed, PhD, FRCVS, DVSc, MA, VetMedDr (h.c.); C. Wayne McIlwraith, BVSc, FRCVS, PhD, DACVS, DECVS; and Paul Rene van Weeren, DVM, PhD, DECVS (Vet J. July 2013) proposes a simplifying classification system to help to better address etiology and therapeutic intervention.

Joint disorders within the syndrome of juvenile osteochondral conditions, also referred to as JOCC, are classified based on the location of the lesion and its biomechanical origin. For example, if the process of endochondral ossification is affected, then it is possible for a young horse to develop osteochondral fragmentation in different locations—one being the surface of the cartilage and another at the peri-articular margin between joint spaces. Or cysts might form within the subchondral bone.

In other cases, an avulsion fracture of epiphyseal bone may occur because of tension on attaching ligaments. Such a lesion may still be considered JOCC, but it is due to an entirely different process than that caused by a disorder of endochondral ossification. In a severe case, there could be collapse of the articular surface altogether while a very different JOCC condition, “physitis,” might result from insult to the growth plate. All of these conditions are clumped under the heading of JOCC, but they are different in how they are managed.

Many of these lesions are identifiable with radiographic evaluation, so radiography remains as a great adjunctive tool for veterinarians to use in a lameness workup on a young, growing horse, particularly one that is exhibiting lameness and/or joint effusion. Further studies have been pursued to assess the heritability of JOCC, in particular in French Trotters. Another study is documenting occurrence of JOCC in Thoroughbreds, Standardbreds and Warmbloods.

Data collected from this research may provide breeders with genetic information to help cull breeding prospects if they pose a risk of passing on genetic traits that favor development of JOCC.

While OC lesions are elicited by multifactorial etiologies, including diet and exercise, identification of genetic lines with a heritable proclivity can help outline breeding strategies to minimize occurrence of JOCC. This has significant economic impact since any developmental orthopedic disease lesion in a performance or racing horse has the likelihood of detracting from a horse’s future performance, earnings and value.