Here is what I am trying to say.....it says that when they are that bad, they probably never walked correctly....so HOW did her vet miss it?
The following is from:
Knee Problems In Your Dog - Patellar Luxation - Luxating Patella Grade 4
These are pets whose knee cap will not stay in its groove even for short periods. These dogs have a hard time walking. Dogs that have suffered this degree of joint damage for more than a year or two usually have pain, developing arthritis and degenerative joint disease. They usually walk with a crouching stance and stand knock-kneed with their toes turned inward.
Grades 3 & 4 generally occur earlier in life. They may not be brought in to a veterinarian for the problem until they are middle-aged, but they usually never walked normally.