Oh dear, here is always something to worry about, isn't there. I avoided this thread to begin with, as I was not sure how I could help, as I have probably breached all the advice from my inexperience. I would definitely do things differently if I could start again, but I do not have that luxury. Rufus was very active when young. He had 3 short walks a day, some up to 30 minutes some longer even as a young puppy, because of his activity levels, and because the then trainer said let him off every walk. He was a very leggy boy. and didn't look much like his show chums. He did not bulk out till between 2 and 3. There is now a query about his hips, at 5, and he has glucosamine as a precaution everyday. He shows no sign of pain, and I hope I have not damaged him. Of course there are always collisions and other accidents to blame as well. If I was starting again, I would restrict exercise. But as others have said, when a cocker naturally runs like a whippet and keeps up with bigger dogs as he plays, it seems harsh to stop him. Oh yes, I have also been advised to stop the throwing of bouncy balls, which Rufus loves and always has done because he can jump and catch the ball as it bounces. The aerial twist and landing is not a natural movement and puts strain on the hips, apparently. So I would restrict exercise to short walks with some training, and build it up. I would use the lead and a long lead more, and I would use a dummy and not a bouncy ball. But who knows whether things would be better? And I would probably still be worried about something.