Hyper extension of the hock joint?

i have a 10 month old dalmatian with back leg problems, i have noticed his hock joint is very straight when he stands, iv done some research and found that it is most likely hyper extention of the hock joint, i was just wondering if anyone knew what problems this could cause and what i could do to try and improve the problem? he has been to the vets and had xrays etc and everything comes back clear, they don't seem to know whats wrong, the only thing that's seems to be wrong with his legs is that they are very very straight they don't seem to hurt him and iv had a good look and it doesn't bother him, but they seem to click at that hock joint and he does get stiff after running aroundif anyone has any ideas on how i can help plz let me know!

Structure is inherited: A straight stifle = long hock. In some cases, if the ligaments are loose, you can see the hyperextension of the hock joint past vertical. Dogs with extremely straight stifles are prone to more patella problems and ruptured cruciate injuries.