On each wing of the pedal-bone is a large elastic plate of cartilage, the upper margin of which can be distinctly felt above each side of the hoof towards the heels of the foot, and the use of which is very important in giving springiness to the movements of this part of the limb.
In some horses - and more especially those which are coarse bred - these become rigid or ossified, either through wearing shoes with high calkins or from concussion on hard roads, this change usually taking place in the fore-feet. With slow-paced horses this alteration is not of so much consequence as with riding or harness horses, in which it usually causes lameness.
If it causes lameness the horse generally steps short, and throws his weight more on the front than the back part of the foot; and the condition of the cartilages may be readily detected by pressing them with the fingers immediately above the hoof, when they will be found hard and unyielding.
At the commencement, if inflammation is present and the alteration suspected to be taking place, fomentations and poultices should be employed, followed by blistering, or firing as a last resource, should the lameness not disappear. If this does not effect a cure, then special shoeing must be resorted to, as bar or periplantar shoes, to allow the frog to sustain weight.