You could start with Promaxol and then switch over to Arthro-IonX when you feel things are progressing well. As you see improvement it would also be good to begin to lower the Rimadyl dosage since it is harder on the liver and kidneys. Because she is becoming weak in the rear end I would suggest you give a choline product such as Geri-Form which will help the nerves going there. You can get that from your veterinarian. I also like to use a few other supplements for dogs in similar circumstances. Give digestive enzymes with each meal, and probiotics, MSM, and a fish oil supplement daily. Both Promaxol and Arthro-IonX help the body better utilize the additional supplements for a synergistic effect. Please let us know of your progress or if you have any other questions.