Arthritis literally means “inflammation of a joint.” In some forms of arthritis, such as osteoarthritis, the inflammation arises because the smooth covering (articular cartilage) on the ends of bones become damaged or worn. Osteoarthritis is usually found in one, usually weightbearing, joint.
In other forms of arthritis, such as rheumatoid arthritis, the joint lining becomes inflamed as part of a disease process that affects the entire body. Some other types of arthritis are: seronegative spondyloarthropathies, crytalline deposition diseases, and septic arthritis.
Arthritis is a disease of the joint. A joint is where the ends of two or more bones meet. The knee joint, for example, is formed between the bones of the lower leg (the tibia and the fibula) and the thighbone (the femur). The hip joint is where the top of the thighbone (femoral head) meets a concave portion of the pelvis (the acetabulum).
A smooth tissue of cartilage covers the ends of bones in a joint. Cartilage cushions the bone and allows the joint to move easily without the friction that would come with bone-on-bone contact. A joint is enclosed by a fibrous envelope, called the synovium, which produces a fluid that also helps to reduce friction and wear in a joint. Ligaments connect the bones and keep the joint stable. Muscles and tendons power the joint and enable it to move. There are two major categories of arthritis.
The first type is caused by wear and tear on the articular cartilage (osteoarthritis) through the natural aging process, through constant use, or through trauma (post-traumatic arthritis). The second type is caused by one of a number of inflammatory processes.
Symptoms of Arthritis
Regardless of whether the cause is from injury, normal wear and tear, or disease, the joint becomes inflamed, causing swelling, pain and stiffness. This is usually temporary. Inflammation is one of the body’s normal reactions to injury or disease. In arthritic joints, however, inflammation may cause long-lasting or permanent disability.