A horse that wants to collapse and stop hard puts so much effort into it. It's like a weight lifter doing a powerlift, packing 200 to 300 pounds of rider and saddle, going 30 miles per hour and shutting it all down, and holding it. The hock and fetlock joints are probably the most frequently afflicted areas. Problems in the stifle and hip area can wash the horse out, because of the demands of the sport. With the hock as the primary problem area, bone spavin is common.
Some horses develop bog spavins.
Such conditions in the hock can lead to back problems, with the horse protecting himself in the stop. Bartlett sees hind end lamenesses associated with stopping and spinning. The wheel can start anywhere, in the hocks or front feet. The horse that is sore behind also tends to be sore in the front feet, if he continues to be used. The horse will travel similar to a hock lameness.