imo , as far as elbows , genetics , proper food and growth rate is about the extent of your control ...... as for hips , walk that puppy and walk him a lot ...... a 3-4 month old puppy , at least mine , have no problem walking 2-3 miles at their pace ........ i'm sure pups that are allowed free range in a large yard end up on average with better hips than restricted pups , pups with free range and littermates i think is the best way to raise them , they need their strength to keep up with their growth , and their growth is fast , it takes constant proper exercise with the proper amount of rest , you should never push a pup physically ....... not a lot of folks have the ability to give a pup free range 24/7 , so keep the pup on their legs , moving as much as you can and they want ....... it's pretty much been proven that pups with greater muscle mass in their rears on average have better hips ....... pups shouldn't be encouraged to run hard , cut , and jump , there is no way to stop it , but don't encourage it ........ a pup that moves well can trot without a problem , a proper trot is not excessive impact , walking up hills is not excessive impact , i believe it is less impact than walking on flat ground and better exercise .......... walking downhill is a bit more impact on the front but slow down hill should mitigate that ........ exercising dogs and pups , especially pups is a skill ....... most folks either do to little , to much , or inappropriate types .......... imo it would be hard to overdo appropriate types of exercise with a pup , much easier to do too little ............