August 2005

Flexible, Fragile Shock Absorbers: Knees

The horse’s knee is like our wrist, except our wrist doesn’t have to support tremendous weight under tough conditions.

We pay attention to our horses’ knees but forget their relative fragility.

It’s amazing the amount of punishment the horse’s knee—or “carpus”—can take, especially when you actually look at how it’s put together. The radius, the major bone of the upper arm, is balanced on two rows of small bones called the carpal bones, which are in turn perched on top of the horse’s cannon bone and the head of the medial (inside) splint. This arrangement allows the knee to flex freely, but it doesn’t look too stable.

Stability is achieved by multiple ligaments that connect the carpal bones to each other, as well as others that run from the radius to the carpal bones, the carpal bones to the cannon bone…