Arthritis means inflammation of the joints. It is a term used when joints are painful and/or lose their normal motion. The most common cause is osteoarthritis, which is primarily a wear-and-tear issue. All joints can be affected although the knee is the most commonly reported. There are around 30 joints in the foot, with those most commonly affected with arthritis found across the inner midfoot/arch and at the big toe joint. For more on big toe joint arthritis, click here.