Arthritis is a common condition that affects millions of people around the world. It involves an inflammation of one or more joints (where bones connect), which leads to pain, stiffness and difficulty in moving.

A movable joint consists of ends of bones lined by cartilage and connected to each other by ligaments. A joint capsule which consists of a tough membrane encloses the joint. Inside the joint is the synovium, a thin membrane that secretes a fluid that lubricates the joint and provides nourishment to the cartilage. Muscles and tendons support the joint and allow movement while keeping it stable. There are different conditions which can affect the joint and cause inflammation, commonly known as arthritis.

There are different types and causes of arthritis, and the two most common types are osteoarthritis and rheumatoid arthritis.

What Causes Arthritis?
Joint inflammation may be brought about by a wide variety of factors that cause damage to one or more elements in the joint. The causes of arthritis vary according to the type of arthritis:

This type of arthritis is caused by the natural wear and tear that affects the cartilage lining the bones in the joint. When the cartilage thins out and wears away, the bones may rub against each other, causing swelling and pain. Osteoarthritis usually affects one joint, although it can occur in more than one part of the body.

This is usually due to degenerative changes associated with aging, and the condition is often experienced starting at middle age. The knee and hip joints are most commonly involved, although other joints may also be affected.

Aside from normal changes due to aging, other factors, like overuse, can bring about damage to the joint cartilage. For instance, a knee injury or infection can lead to changes in the joint, leading to osteoarthritis.

Factors that can increase the risk for joint inflammation due to osteoarthritis include obesity, which increases stress on a weight-bearing joint, gender (females are more likely to be affected) and family history of arthritis.

Rheumatoid Arthritis
Chronic joint inflammation resulting from the immune system attacking itself is the cause of rheumatoid arthritis (RA). In this condition, the hands, wrists and knees are commonly involved, and in serious cases, the immune reaction also affects other parts of the body such as skin, nerves, eyes and lungs. This type of joint inflammation is usually distinguished from osteoarthritis by the occurrence of joint swelling and pain in symmetry, thus involving both sides of the body. It is also characterized by stiffness which is usually noted in the morning or after long sitting.

Gouty Arthritis
A third type of arthritis that is less common than osteoarthritis and RA is gout, and the cause of joint inflammation is the accumulation of uric acid crystals in the joint. Uric acid is a byproduct of metabolism which in some individuals is not eliminated efficiently. What causes arthritis in this condition are the needle-like crystals which are deposited commonly in the large toe joint, the knee or the wrist, leading to severe swelling and pain.

Other causes of arthritis include infection, such as that found in infectious arthritis, while in others, the cause may be genetic or unknown, such as that of juvenile arthritis.