The Arthritis Foundation* (arthritis.org) mentions curcumin as a supplement that eases symptoms of arthritis. However, curcumin represents only a small portion of turmeric and has low absorption. They recommend checking the standardized amount of curcumin to choose brands with better absorption like Theracurmin®.
A clinical study entitled "The Efficacy and Safety of Highly-Bioavailable Curcumin (Theracurmin®) for Treating Knee Osteoarthritis," a 6-Month Open-Labeled Prospective Study, showed beneficial effects of Theracurmin® on various types of knee osteoarthritis.