Horse anatomy
Cannon Bone
The long bone in the lower leg. Supports weight and movement.
A closer look
The cannon bone is the long, straight bone in the lower leg, between the knee or hock and the fetlock. In the front legs it is the third metacarpal and in the hind legs the third metatarsal. Two thin splint bones run along its sides, and important tendons run down the back of the leg behind it.
Why it matters
The cannon bone and the tendons behind it carry the horse's weight with every step. There is very little muscle in the lower leg, so it is easy to bump and slow to heal, which makes daily leg checks important.
Care tip
Run your hand down the front and back of each cannon every day. Learn how cool, tight, and smooth the legs normally feel so you notice new heat, swelling, or bumps and can tell an adult right away.
Common mistake
An old, hard bump on the side of the cannon, called a splint, often looks worse than it is once it has settled. A new, warm, or sore bump should still be checked by a vet.
Fun fact
The thin splint bones beside the cannon are tiny leftovers of extra toes that the horse's ancient ancestors had.