He is undermuscled and maybe underfed looking. See how his spine is kind of sticking out of his back? And his neck is very much under muscled.
His back legs are camped under in a a sickle hocked stance. Did you square him up properly? And his front legs appear to be base narrow, but again, did you square him up properly? It's important that you don't take the photo from a downward looking angle. You need to be taking it from directly off to the front or side, at a horizontal plane.
There appears to be some kind of swelling on his right hock , just under it. Has he some lameness? His legs in general look kind of swollen, or maybe just lacking in definition. Hard to see the joints very well.