This subject came up at a dog show, a year or so ago. A lady had purchased an Aussie Bulldog puppy and was having the same issues as your having. A lady who breeds Great Danes suggested that she has a look at the following page:
http://www.greatdanelady.com/articles/knuckling_over.htm
I'm pretty sure its an American site but some of the information may be of use to you. It might also be handy to share this information with your vet as they may be able to access some of the suggested food/supplements and may take you through the taping process described on the link. I hope this helps your beautiful puppy.
