One of my dogs has developed a very clicky hock lately. She never limps and never seems to be in pain, but it clicks when she walks and when I flex it. She's only 2 years old, and very fit and energetic. I have given her a joint supplement as a preventative measure since she was a puppy, as she is fairly large (55lbs). Part of me thinks if she's not limping, it's not a problem, but she's a SAR dog and I don't want an injury to cut her career short. Does anyone have any ideas what might be causing this?