What is sidebone?

• A. Inflammation of the navicular bone
• B. Ossification of the cartilages of the P3
• C. Fracture of the coffin bone
• D. Separation of the hoof wall from the sole

Answer: (B)

Sidebone is the ossification of the lateral cartilages that extend from the coffin bone (P3) toward the hoof wall. These cartilages harden into bone, producing the bony enlargements along the sides of P3. This definition matches the option that describes ossification of the cartilages of the coffin bone. It isn’t inflammation of the navicular bone, a fracture of the coffin bone, or separation of the hoof wall from the sole. In many horses, sidebone is an incidental finding and may not cause lameness, though severe ossification can affect hoof flexibility and, in some cases, contribute to discomfort or other hoof problems. Management generally involves regular trimming and shoeing to maintain balance and monitoring for any signs of pain.