Osteochondrosis/ Osteochondrosis Dessicans
Osteochondrosis (OC) falls within the constellation of developmental orthopedic disorders and is very common in horses as well as other species. OC is caused by a failure of normal cartilage development at the end of long bones (such as those found in the legs) and vertebrae (in the neck and back). Sometimes, the disease is associated with a bone/cartilage fragment visible on radiographs (x-rays) and in those cases it is referred to in as osteochondrosis dessicans, or OCD. OC has been diagnosed in nearly all joints in the horse, but certain joints are commonly affected. These include the hock, stifle, and fetlock. Affected horses are generally diagnosed at a young age (as yearlings on pre-purchase radiographs, or soon after being put in training). The most common clinical sign is excess fluid in the joint (effusion). Lameness can occur with this disease, but is not a typical presenting complaint.
Although OC has been recognized in many horse breeds, certain breeds, such as Warmbloods and Standardbreds are commonly considered to be predisposed to the problem. Large-scale pedigree studies in Warmbloods have demonstrated that there is an inherited component for this disease. However, disease manifestation certainly involves a complex interplay of genetic background and environmental factors such as diet, growth rate, and exercise.
We are harnessing molecular genetics technology to try to identify the gene(s) underlying susceptibility to this complex disease. Our current focus is on hock OC in Standardbred trotters, but the results of our research may be applicable to the general population of horses afflicted with OC. Better understanding of the underlying causes of OC may lead to better management of affected horses.
This work is funded by the Minnesota Agricultural Experiment Station “Program in Equine Medical Genetics”
Mccoy, Annette M., Samantha K. Beeson, Rebecca K. Splan, Sigrid Lykkjen, Sarah L. Ralston, James R. Mickelson, and Molly E. Mccue. "Identification and Validation of Risk Loci for Osteochondrosis in Standardbreds." BMC Genomics17, no. 1 (2016).
McCoy, A. M., Ralston, S. L. and McCue, M. E. (2015), Short- and long-term racing performance of Standardbred pacers and trotters after early surgical intervention for tarsal osteochondrosis. Equine Veterinary Journal, 47: 438–444. doi: 10.1111/evj.12297
Lykkjen, S., Dolvik, N. I., McCue, M. E., Rendahl, A. K., Mickelson, J. R. and Røed, K. H. (2013), Equine developmental orthopaedic diseases – a genome-wide association study of first phalanx plantar osteochondral fragments in Standardbred trotters. Animal Genetics, 44: 766–769. doi: 10.1111/age.12064