
My boy had this issue as a youngster, I found he didnt tighten up until I started running or biking daily with him trotting in front on his harness. I also took him to the chiropractor and she found his pelvis was out which meant he wasnt working the right muscles in his legs which made his movement look wobbley.
Its always worth getting a chiropractor to take a look, its amazing what a difference a small tweak can make.