We have noticed lately that our 9 yr. old boy has theses large, bone-hard roundish ankle joints (hock, tarsus?) on his hind legs. They are on both legs and are larger on the inside of the joint, The dog is somewhat overweight, and he has a bit of a hard time getting up, but still loves to run and play like a puppy. He does not limp. These places do not appear to hurt him when I rub and push on them. Are these joints normal for bigger breeds, or are these something that has developed because of his weight? Our other 11 yr old GR doesn't have these, but he is not overweight.