When soft tissues in the horse’s pastern or heel are subjected to repeated strain or trauma, the horse’s body may respond to the chronic inflammation by depositing calcium. If the strain or concussion continues, the result may be ringbone, calcification affecting the collateral and suspensory ligaments along the front of the pastern, or sidebone, calcification of the lateral cartilage at the sides and rear corners of the horse’s heel.
Ringbone is seen most often in older horses whose careers have involved repeated concussion or twisting, actions that put strain on the joints in the pastern. Jumpers, parade horses, equines ridden or driven on hard surfaces, and barrel horses are prime candidates. Horses that have conformation faults such as small feet and upright pasterns are also at increased risk. Ringbone can affect the coffin (low ringbone) or pastern (high ringbone) joints. Low ringbone carries a much poorer prognosis for athletic activity than high ringbone.
Ringbone causes lameness that progresses if work is continued and the strain is not relieved. If management is not changed, the calcification will become visible as a hardened ridge of bone across the front and sides of the pastern. Ringbone usually affects both forelimbs, though lameness may be more severe in one hoof than in the other.
If it is detected in its early stage, ringbone can be treated by therapeutic trimming and shoeing to balance the hoof. Pain medications and joint injections of glucosamine can make the horse more comfortable. Ringbone that is more advanced has a less positive prognosis because bony changes in the hoof may restrict movement of the pastern joint. Horses with low ringbone are rarely able to perform at a high level, though they may be able to do light work.
Sidebone can be caused by the same conformation faults (particularly, a heavy horse with small feet) and types of strain as ringbone. Trauma such as a kick can cause also inflammation that leads to sidebone. Some degree of mineralization of the collateral cartilage also occurs normally with age. Horses usually don’t become lame from this condition, and the calcification can be felt but is not seen as readily as ringbone. The presence of sidebone may not affect the horse’s usefulness, but it is a sign that the horse’s career has caused considerable strain or force that has affected the hooves and lower legs. Prudent owners might want to consider cutting back on strenuous exercise programs and observing for any lameness to ward off unsoundness in the future.