Cartilage is a tough, but flexible, tissue found in many locations in horses’ bodies, such as in joints and between bones. Bone, on the other hand, is a rigid tissue that makes up a horse’s skeleton. Both are important structures, but they serve different purposes. So what happens when cartilage ossifies (hardens into bone)?

At the 2015 World Equine Veterinary Association Congress, held Oct. 8-10 in Guadalajara, Mexico, Sue Dyson, MA, VetMB, PhD, DEO, FRCVS, presented the results of a study to determine whether ossified ungular cartilages are a clinically significant finding in horses. Dyson is the head of clinical orthopaedics at the Animal Health Trust Centre for Equine Studies, in Newmarket, England.

The ungular cartilages are located on either side of the coffin bone in the horse’s hoof and are thought to aid in shock absorption, support of the back of the foot, and venous return. When this structure ossifies, veterinarians know there is an increased risk of injury to the collateral ligament of the coffin joint and other nearby structures. Further, ossified cartilages are less able to dissipate energy from the ground reaction, also predisposing the horse to injury. But veterinarians weren’t sure whether ossified ungular cartilages themselves would prove to be a clinically significant finding on radiographs.

So Dyson and Laura Jones, BVSc MRCVS, a junior clinician at the Centre for Equine Studies, reviewed radiographs of 1,255 front feet and narrowed the study field to 386 hooves on 271 horses. All the included feet had ungular cartilages that scored 2 or higher on a 0 to 5 scale (with 5 being the most severe and 0 being no ossification). During their evaluation, Dyson and Jones determined the shape of the ossified cartilage, as well as which radiographic views they were best evaluated on and any other abnormalities noted on the X rays. They also noted whether there were any significant associations between the ungular cartilages and lameness and other abnormalities