Yes, I know this photo has been going around for a while. But I wanted to bring up something really important about these kinds of joints (ginglymus or hinge joints). Take your finger. Try to move it forward and back. It works, right? It glides smoothly, providing you don’t have joint deterioration or damage. Now try to move it side to side, and you’ll see that it will move just barely but resists and becomes uncomfortable at a certain point. That is because those joints in your finger are ginglymus or hinge joints, and they move on only one plane (forward and backward). Now imagine walking on that imbalanced finger, like your horse would. Ouch.
*This* is why those who say “imbalance is natural” to criticize balanced/corrective barefoot trims are wrong. The *only* way imbalance is natural is if the bone itself is deformed, and even that is often a product of poor management early in the horse’s development. But imbalance that involves uneven joint spacing is so, so, so wrong and leads to long term deterioration of the joints and premature death in equines.