This helps men obtain a harder erections and for them to be maintained for a longer period of time. Cnidium also helps promote better blood circulation. Which we need to look at next... The most commonly affected joints are those in: hands, spine, knee, buttocks A rheumatologist is a physician who specializes in nonsurgical treatment of rheumatic diseases, especially arthritis. Osteoarthritis initially affects the smooth cartilage lining of joints. This makes exercise more difficult than usual, causing pain and stiffness.