Dogs with joint problems respond well to supplements such as glucosamine and chondroitin sulfate; one brand that springs to mind is Cortaflex which comes in preparations for humans, dogs and horses.
1000mg of Fish Body Oils per day may be better than CLO as there is not the Vitamin A and D problem. Vitamin C with bio-flavenoids, Vitamin E and germanium may also be of assistance.
Obviously being overweight puts extra strains and stresses on the joints which is not very helpful.
The link below maybe of assistance.
http://www.bowchow.com/arthritis.htmlAlso if you feed veggies you might want to steer clear of the nightshade family eg potatoes, tomatoes, peppers, aubergines etc as these are thought to aggravate the condition.
HTH