A good friend of mine, who is in his early 50's, suffers from some type of arthritis in both knees. Realistically, he is a prime candidate for full knee replacements. However, he has about 5 more years to work and doesn't want to have the surgery fearing it might force him to retire prematurely. He's already had all of the injections that work temporarily.
He really wants to get back in shape, but doesn't know what to do for lower body workouts since practically all of the conventional exercises cause pain. He is probably 30 pounds overweight, so I suggested getting weight down. Beyond that, I don't know how to help. Any suggestions?