I found this helpful.

http://cal.vet.upenn.edu/projects/saortho/index.html

This is a very good book on orthopedics in dogs. One thing that I found interesting was when he did an x-ray of a joint and then did the x-ray with the jointed stressed. The first x-ray looked normal but in the stressed x-ray , you could see the problem. Anyway, in case you have nothing better to do then read a text book on canine orthopedics. Here is the site.