Hi Jon:
I'm not an expert on this, but I found the following on the website for the Orthopedic Foundation for Animals (OFA)
With weight control, the goal is to prevent the dog from becoming overweight to reduce mechanical stresses applied to the hip joints. In general terms, the ribs should be easily palpated and there should be an indentation in front of the pelvic wings (waist line).
Controlled exercise is indicated to prevent or relieve the inflammatory process that leads to the pain associated with arthritis. The amount and difficulty of the activity is determined on a trial and error basis. Exercise should start with short leash walks and be gradually increased until the dog reaches the desired level of activity. If clinical signs start to reappear, the amount of exercise is scaled back to a level that will not cause clinical signs. Overall, exercise should fit to an individual dog's maximum intensity level with the goal to maintain muscle tone and cardiovascular function without causing pain, stiffness, and inflammation to the joint. The right amount of exercise helps to maintain muscle tone and strength and stabilizes the unstable dysplastic joint. Exercise also improves joint range of motion which in turn, keeps the dog more comfortable. Swimming, because it is a non-weight bearing exercise, can be a very useful means of maintaining muscle tone and range of motion without placing concussive forces on the joint.
Keep the dog in a warm environment. Warmth tends to help control the pain of arthritis from hip dysplasia. As in people, arthritic pain in dogs tends to be worse in the damp and cold of winter. Providing a well-padded and warm bed will help alleviate some of the pain associated with osteoarthritis. An egg-crate foam bed for dogs is commercially available. Applying superficial heat in the form of heating pads may also relieve pain. Care must be taken not to burn the skin especially with an electric heating pad. Heat works best for chronically inflamed joints from arthritis while cold works better to treat acute (sudden) types of joint injury.
Hope this helps.