Hip dysplasia in dogs
Hip dysplasia is a degenerative joint disease common in dogs especially big or larger dogs. A normal pelvis in a dog contains the hip and where the hind legs go into that hip a socket is formed. Between the head of the large bone of the hind leg (femur) and the hip there are different types of soft tissues that allow the leg to move and rotate so that the dog can walk run, jump, sit etc.
Hip dyslasia happens when the pelvic joint develops abnormally. It happens in puppy hood and you can usually see it in an x-ray at the age of 2. What happens is that the head of the femur (leg bone) moves away from the hip just a bit. Then, when the dog moves his leg, the head of the femur grinds away against the soft tissues that connect it to the hip. Over time, the grinding eats away at that soft tissue until both bones become separated.
Usually hip dysplasia in dogs shows itself in mid-life. The dog starts to walk slightly funny, then really funny - until it is extremely painful to walk or move. Other symptoms include leg shaking during sleep.
There are some things that your vet can try if your dog has hip dysplasia, (total/partial hip replacement, injections) but unfortunately, right now the options aren't great.