Types of Arthritis. Arthritis is a condition describing inflammation of a joint, and applies to over 100 diseases that have been identified to date. Most of these diseases fall into one of two categories: degenerative arthritis, such as osteoarthritis, or inflammatory arthritis, such as rheumatoid arthritis. Symptoms of most types of arthritis include pain, stiffness, and swelling in the joint. Explore symptoms and treatments information for your arthritic condition from the topics listed below. Topics