Tai chi is a Chinese system of exercises that dates back thousands of years. It is practiced through a series of slow moving poses originally designed for self defense and mental calm and lucidity through its graceful circular movements and breathing techniques. Though the effects of tai chi lack much scientific study, it is believed to increase flexibility, strengthen muscles, develop balance and improve range of motion. [source: MedicineNet].
There are other reasons for people with arthritis to practice tai chi, including because it's low impact, has a low risk of injury and can be done indoors or outdoors, depending on your mood. It can also be practiced alone or in groups. But if you don't know where to start, check out the Arthritis Foundation's Tai Chi Program.