The two main types of arthritis — osteoarthritis and rheumatoid arthritis — damage joints in different ways.

Osteoarthritis

The most common type of arthritis, osteoarthritis involves wear-and-tear damage to your joint's cartilage — the hard, slick coating on the ends of bones. Enough damage can result in bone grinding directly on bone, which causes pain and restricted movement. This wear and tear can occur over many years, or it can be hastened by a joint injury or infection.

Rheumatoid arthritis

In rheumatoid arthritis, the body's immune system attacks the lining of the joint capsule, a tough membrane that encloses all the joint parts. This lining, known as the synovial membrane, becomes inflamed and swollen. The disease process can eventually destroy cartilage and bone within the joint.

Jan. 22, 2013