Whether you need a firm or soft mattress depends on your sleep position. Side sleepers need a soft mattress to prevent shoulder and hip pain. That goes double for side sleepers who also have arthritis.
The best mattress for arthritis patients who are back and combo sleepers is a medium-firm because these sleep positions require a mix of support and cushioning to maintain proper spinal alignment.
Those who prefer stomach sleeping should look into a firm mattress. These are the best mattresses for people who need extra lift to maintain healthy spinal alignment.