My brother's opinion is that owners/environment contribute to orthopaedic problems more than you would think. While many dogs, particularly purebreds, may be predisposed to hip/knee problems, dogs that trained to repetitively sit or stand at very young ages, are fattened up to mature body weight before 24mos, taught to jump up into beds of trucks young, run hard in the field, etc before their bones/joints are mature result in a lot of the problems he treats.
Of course its a fine line as much of veterinary medicine involves training the owners
