In complicated ulcers, which joint is most affected?

• A. Fetlock
• B. Coffin
• C. Pastern
• D. Stifle

Answer: (B)

In complicated hoof ulcers, the coffin joint is most affected because of its direct relationship to the sole and white line. The coffin joint, or distal interphalangeal joint, sits directly beneath the distal phalanx and just behind the solar surface. When an ulcer deepens, the hard barrier between the sole and the joint capsule is the first to be breached, allowing inflammation (and potential infection) to extend into the joint space. The pastern and fetlock joints are located higher up the limb and are not as readily invaded by a lesion that starts at the sole, while the stifle is far away from the hoof altogether. So, the anatomical proximity of the coffin joint to the site of the ulcer makes it the most commonly involved in deep, complicated ulcers. If there are signs of joint involvement such as swelling or heat around the coffin joint, it suggests that the ulcer has extended deeper.