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Thanks again Lankeela, yes the woman we got him from did point out the "Queen Anne" legs on the mother but tbh I was so entranced with the pup we had gone to view (not to mention totally inexperienced when it came to buying a pup) that I didn't think of the possible problems in later life.
And yes he is very barrel chested, its in both legs, one more prominently than the other. Sometimes when he is sitting it looks as if there is abnormal stress on the joint,which is what worried us.
What is your breed? I'd assumed it was Alsation from your avatar.