HOD is an orthopedic disease seen in medium, large, and giant breeds, more common in some than others. There may be several causative factors including heredity, infection, and possibly vaccines, with contributing factors being both genetic susceptibility (“weakness”) and calcium supplementation or unlimited/excessive feeding of pups resulting in mineral overloading as an intensifier of pain and abnormal bone growth.
As in the case of panosteitis, the disease appears to be both self-limited and transient, independent of treatment. Although there are rare deaths, probably due to “complications”, most pups outgrow HOD within one to a few months. The fatality rate is too erratic to reliably measure. In some reports it has been 25-35% (almost certainly inflated via poor statistics and diagnoses) and in others it was less than 4%. In every case, it is traumatic because of the pup's pain and the owner's helplessness and frustration.
Multiple relapses are not uncommon, and the same bones can be affected more than once. Extraperiosteal calcification is slowly resorbed and radiodensity of the affected limbs returns to normal or nearly so. Some individuals are left with permanently bowed forelegs because the ulna has grown at a different rate than the radius (as is the case in some elbow dysplasias), and some are cowhocked for life. Most, however, endure and survive the effects of HOD without permanent damage.[/b]