knee pain while sitting and driving Simply defined, arthritis is inflammation of a joint. In an arthritic shoulder, inflammation causes pain and stiffness. This article looks at the five different types of ...Shoulder Arthritis. Arthritis is damage to the cartilage in joints. Shoulder arthritis occurs when the cartilage starts wearing down on the ball and/or socket sides of the shoulder joint. Symptoms of shoulder arthritis may include pain in the shoulder joint, stiffness and reduced range of motion.