Cow hocks is exactly what our regular vet and the orthopedic specialist we see calls it. I noticed it with Max, when we got him and assumed it was just him growing. Now, sometimes when I look at him, they appear to be slightly turned in, sometimes they are perfectly straight. We also noticed it, although much more pronounced and constant in Cody. It turns out that it can be an indicator or bad hips, knees, ankles, or all three. With Cody, he has a very bad hip that we are going to have to replace. The dog we are trying to place appears to have it slightly, but his x-rays are clear. The vet feels his is just not enough muscle and he was starving when we found him. From what I have experienced, heard and read, cow hocks, can be an indicator of a lot of different things, including bad breeding, bad nutrition, growth phase, bad hips, knees or ankles, or they indicate nothing at all. Hopefully, your pup is just growing and his are slightly loose right now.
Kathy