Panosteitis is known to be a problem in young bassets. Intermittent, shifting lameness is characteristic of this condition.
Some links:
Panosteitis (Vetcentric)
Panosteitis (Smith and Foster, discussion of causes is a little bit dated)
Panosteitis (Provet)
Some other causes of forelimb lameness in young dogs:
Elbow Dysplasia
Premature physeal closure, where the growth plate of one of the bones in the forelimb closes prematurely. The affected bone stops growing, while the other continues to grow and eventually becomes bowed.
Some links:
Panosteitis (Vetcentric)
Panosteitis (Smith and Foster, discussion of causes is a little bit dated)
Panosteitis (Provet)
Some other causes of forelimb lameness in young dogs:
Elbow Dysplasia
Premature physeal closure, where the growth plate of one of the bones in the forelimb closes prematurely. The affected bone stops growing, while the other continues to grow and eventually becomes bowed.