I agree with Sqad, if its osteo, not rheumatoid arthritis, then the joints are actually wearing away. Weight bearing exercise won't help and could actually speed the process up. Better would be swimming, some of the gentler kinds of yoga, pilates.
Chris, that website isn't unbiased and also refers to cycling as a non load bearing exercise which is deffo wrong. After joint replacement and assuming all is well, cycling can be a good way to rebuild lost muscle tone but in Lurcher's circ's I would be doing my best to conserve the joint and not wear more away.
They are right about maintaining and increasing muscle tone though