Types

• The most pervasive type of arthritis is rheumatoid arthritis, where the immune system mistakenly attacks the joints and other parts of the body. Particularly painful episodes, called "flare-ups," occur when the joints warm up from an extra flow of blood to the area, causing stiffness, swelling and severe pain.
  Another type of arthritis is osteoarthritis, caused by cartilage, which normally supports joints, becoming brittle and weak. The bones underneath the cartilage then try to make up for the deficiency by thickening and spreading out, causing knob-like growths known as osteophytes. When the cartilage weakens further and breaks away from the bones, the bones can rub together, causing severe pain.
  
  

Risk Factors

• Though the actual cause of arthritis is unknown, several factors can predispose one toward arthritis: being over 55 (arthritis is very uncommon in people under 40), being overweight, being a woman (two-thirds of all arthritis cases are found in women) and having prior injury to or strain on the joints.