A horse’s capped hock can just be a cosmetic issue, but without further examination, it could also be a bigger problem.
For the answer to this question, the American Association of Equine Practitioners consulted Dr. Kerry Beckman.
An uncomplicated capped hock is considered to be only a cosmetic problem for the horse and will not affect athletic performance. However, if there are underlying complications, such as infection or damage to nearby bony or soft-tissue structures, there may be a detrimental effect on performance.
When purchasing a horse with a capped hock, I recommend having the area evaluated by radiography and ultrasonography to ensure that there are no other lesions present.
— Dr. Kerry Beckman, member of the American Association of Equine Practitioners