Which of the following allows a horse's hoof to twist or move from side to side?

The short pastern bone plays a crucial role in the flexibility and movement of a horse's hoof. It is one of the key bones in the equine limb structure. Its unique position and shape enable a certain level of articulation at the joint where the short pastern connects to the long pastern. This joint allows for the hoof to twist and move from side to side, providing essential flexibility for the horse's gait and aiding in the absorption of shock and adaptation to varying terrain.

The short pastern bone's design contributes to the overall functionality of the hoof, assisting the horse in maintaining balance and stability while moving. This ability to twist or move enhances the horse's agility and performance, particularly in activities that require quick changes in direction or speed.

In contrast, the navicular bone mainly serves as a shock absorber for the hoof and does not facilitate side-to-side motion. The metacarpal bone supports the horse's weight but does not allow for hoof movement. The dewclaw, which is a small digit found on some animals, does not play a role in hoof movement at all, as it is not functionally significant in horses. Thus, the short pastern bone is the correct choice because it directly influences the hoof's ability to flex