Negative plantar angles seem to be fairly common in the hind feet of horses that are asked for a lot of collection.
Lateral radiographs are the best diagnostic tool to determine whether a horse has a negative plantar angle. However, if one isn’t available, try this method.
Draw an imaginary line starting at the lateral bulb of either hind foot through the coronary band and continuing forward (Figure 1).
Where does the line bisect the front limb?
If the line is below the carpus, then most likely you are not dealing with a negative plantar angle.
If the line bisects the limb between the carpus and the elbow, then there is reason for concern. If your imaginary line is above the elbow, then most likely you are dealing with a negative plantar angle. The farther up the limb the line bisects, the greater the likelihood of a negative plantar angle.