E Q U I N E AT H L E T E
Hock Injuries Trauma, stress, disease and conformation can be factors By Heather Smith Thomas
The hocks of performance horses are often under a lot of stress, which can lead to soreness.
The hock is one of the largest, most complex and hardest worked joints in the horse’s body so it must be strong and sturdy to avoid injury. The hock is often under great stress because of the activities we ask the horse to do, and it may be injured during high speed performance. Dr. Olivia Rudolphi (Rudolphi Veterinary Services, in Noble, Illinois) says some of these injuries may be due to developmental/congenital lesions such as an Osteochondritis dissecans (OCD) within the joint— and these might not show up until the horse is put into training and doing more exercise. “Causes of hock lameness can vary between the young horse and the more mature horse. In the young horses we may see a puffy hock or a foal with some sort of insult to the joint. As young horses start training, we may see the hock develop swelling if there is an OCD lesion, and there may be lameness,” she says. Jillian Mills, DVM, DACVSMR (Presidio Equine Sports Medicine & Rehabilitation, Encinitas, California), says hock injuries are interesting because this joint is a combination of high- and low-motion joints.“These joints can undergo different pathological changes that can lead to clinically relevant disease,” she explains.
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“With hocks we will see either acute traumatic injuries, DOD (developmental orthopedic disease) or fatigue-related injuries. Acute injuries often involve fractures, which may include the tibia and cannon bones, as well as collateral and intra-articular ligament injuries,” says Mills. “The upper joint (the high-motion joint) more often has developmental issues such as OCD fragments and subchondral bone cystic lesions. If there is an OCD fragment, the horse may need surgery to have the fragment removed, however this is not always necessary,” she says. “We know that the joint environment is not as healthy as it would be if an OCD lesion was not present. On a pre-purchase exam, for instance it can be difficult to determine whether surgery may be indicated in the horse’s future to remove the osteochondral fragments. For a young horse that hasn’t had the opportunity to prove itself, if we find an osteochondral fragment in a joint that carries excess fluid, and where the horse trots off lame following flexion testing, there’s a higher probability that it will need surgery to remove that chip. The presence of the OCD fragment is an indication that the joint is less healthy, and the horse is more prone
