Most people think of arthritis as the increasing pain and stiffness that comes with age. This form of arthritis is often called osteoarthritis, and can appear in almost any joint in the body, though typical sites are fingers, hips, knees, and spine.  Gout, which can be a precursor to osteoarthritis, causes sudden (rather than progressive) pain in a joint, usually the big toe. More common in men, this form of arthritis is caused by too much uric acid in the bloodstream from eating foods high in purine like meats, fish, gravy, dried beans, breads, and beer. Unlike osteoarthritis, gout pain comes and goes over days, weeks, months and even years, but usually occurs at night.

Infectious arthritis, or septic arthritis, is caused by an infection elsewhere settling into a single joint. Those affected are typically older people or young children.  Symptoms include severe pain, swelling, and an inability to move the affected joint or limb.

Rheumatoid arthritis attacks joints on both sides of the body, which distinguishes it from other forms of arthritis. Rheumatoid arthritis can also affect the blood, eyes, heart, lungs, nerves, and even the skin. Like other forms of arthritis, it produces stiffness, joint pain, swelling, and tiredness. It can come on very quickly, or develop over a period of years.

Psoriatic arthritis is a worsening of psoriasis, a painful, itchy skin condition.  Psoriatic arthritis, like rheumatoid arthritis, can be symmetrical (affecting jointed areas like elbows on both sides of the body) or asymmetrical. Psoriatic arthritis causes a red, scaly rash, typically over the hands and feet, but also on knees, elbows, and ankles. It is likely due to genetic factors and immune system failure 40 percent of victims have a relative with psoriatic arthritis. It typically occurs between the ages of 30 and 50, and may be caused either by a bacterial infection, or from taking drugs like lithium, beta-blockers, or anti-malarials.

Lupus is an autoimmune disease often medically associated with arthritis. The linking of two diseases is called comorbidity, and the link between lupus and arthritis is likely the result of a single gene. Both exhibit inflammation, with cutaneous lupus, or ACLE, affecting primarily the joints of the hands.