Ashley Griffin, University of Kentucky
All horses are basically proportional but not necessarily balanced. Balance is the most important characteristic in selection, because it forms the basis for movement, length of stride, and ultimately, performance. Balance is determined by the underlying skeletal structure of the horse. It is important to develop the ability to visualize and evaluate the skeletal system of the horse underneath muscle and other tissues.
The slope of the horse's shoulder is critical in order for a horse to be balanced. Slope of the shoulder changes drastically as the angle of the shoulder increases and decreases. Not only does the top-to-bottom line ratio of the neck change, but the ratio of length of back to length of underline also changes. It is ideal to have a short top line in relation to a long underline.
Physiologically, the straighter the shoulder, the farther forward the withers sit, thus making the back longer from wither to loin. Length of underline from elbow to stifle is not affected by changes in the slope of the shoulder. Therefore, the straight-shouldered horse's body has the appearance of a tube.
Since individual horses are proportional, a horse with a straight shoulder will have a long back, which coincides with a short neck; a short, steep croup; and a steep stifle and pasterns. This conformation will also drastically affect the way a horse moves.