I would go to a good physical therapist and set up an exercise program that works with to help your arthritis. Exercise should include bending, stretching, as well as walking. I have mild arthritis and moving a lot actually makes it better and for me, the pack actually feels good - may be the gentle pressure on the lower back. When you can walk 5-miles a day at home then put on your pack and carry at first 10 pounds, then 15, then 20. 32-35 pounds for a 3-4 day trip is not moderate weight, but heavy. Get your base weight down to 18-20 pounds and then keep food at 1.5-2.0 pounds per day.

Depending on the severity of your arthritis, you may or may not be able to backpack. Also work with your doctor on medications. I would go to a sports-medicine doctor who deals with arthritis in athletes. When I was in my late 30's my regular doctor said I needed to give up activity - I went to a sports medicine arthritis specialist, and she had a whole different take on it. I can control my arthritis quite well with Advil. However, my arthritis is mild and come and go - not continuous. I am really affected by pressure changes and weather.

I like to go solo because nobody is pushing me to do more than my body can take. Some days I can go far and just about beat everyone else on the trail; other days I barely make it 4 miles!