Osteoarthritis
(OA or Degenerative Arthritis)
Medical Author: William C. Shiel Jr., MD, FACP, FACR
Medical Editor: Melissa Conrad Stöppler, MD
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Early, Mild Osteoarthritis of the Hands
What to Do if It Affects You!
Medical Author: William C. Shiel, Jr., MD,
FACP, FACR
Medical Editor: Leslie J. Schoenfield, MD, PhD
 Osteoarthritis is a type of arthritis that is caused by breakdown of
cartilage, with eventual loss of the cartilage of the joints. Cartilage is a
protein substance that serves as a "cushion" between the bones of the
joints. When the cartilage deteriorates (degenerates), the bone next to it
becomes inflamed and can be stimulated to produce new bone in the form of a
local bony protrusion, called a "spur."
A very common early sign of osteoarthritis is a knobby bony deformity at the
smallest joint of the end of the fingers. This is referred to as a Heberden's
node, named after a very famous British doctor. The bony deformity is a result
of the bone spurs from the osteoarthritis in that joint. Another common bony
knob (node) occurs at the middle joint of the fingers in many patients with
osteoarthritis and is called a Bouchard's node.
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What is osteoarthritis?
Osteoarthritis is a type of arthritis that is caused by the
breakdown and eventual loss of the cartilage of one or
more joints. Cartilage is a protein substance that serves as a "cushion" between
the bones of the joints. Osteoarthritis is also known as degenerative arthritis.
Among the over 100 different types of arthritis conditions, osteoarthritis is
the most common, affecting over 20 million people in the United States.
Osteoarthritis occurs more frequently as we age. Before age 45, osteoarthritis
occurs more frequently in males. After age 55 years, it occurs more frequently
in females. In the United States, all races appear equally affected. A higher
incidence of osteoarthritis exists in the Japanese population, while South African blacks, East
Indians, and Southern Chinese have lower rates.
Osteoarthritis commonly affects the hands, feet, spine, and large
weight-bearing joints, such as the hips and knees. Most cases of osteoarthritis
have no known cause and are referred to as primary osteoarthritis. When the
cause of the osteoarthritis is known, the condition is
referred to as secondary osteoarthritis. Osteoarthritis is sometimes abbreviated OA.
What causes osteoarthritis?
Primary osteoarthritis is mostly related to aging. With aging, the water content of the cartilage increases, and the protein makeup of cartilage degenerates. Eventually, cartilage begins to degenerate by flaking or forming tiny crevasses. In advanced cases, there is a total loss of cartilage cushion between the bones of the joints. Repetitive use of the worn joints over the years can irritate and inflame the cartilage, causing joint pain and swelling. Loss of the cartilage cushion causes friction between the bones, leading to pain and limitation of joint mobility. Inflammation of the cartilage can also stimulate new bone outgrowths (spurs, also referred to as osteophytes) to form around the joints. Osteoarthritis occasionally can develop in multiple members of the same family, implying a hereditary (genetic) basis for this condition.
Secondary osteoarthritis is caused by another disease or
condition. Conditions that can lead to secondary osteoarthritis include
obesity,
repeated trauma or surgery to the joint structures, abnormal joints at birth (congenital abnormalities), gout, diabetes, and other hormone disorders.
Obesity causes osteoarthritis by increasing the mechanical
stress on the
cartilage. In fact, next to aging, obesity is the most powerful risk factor for osteoarthritis of the knees. The early development of osteoarthritis of the knees
among weight lifters is believed to be in part due to their high body
weight. Repeated trauma to joint tissues (ligaments, bones, and
cartilage) is believed to lead to early osteoarthritis of the knees in soccer
players. Interestingly, recent studies have not found an increased risk
of osteoarthritis in long-distance runners.
Crystal deposits in the cartilage can cause cartilage
degeneration and osteoarthritis. Uric acid crystals cause arthritis in gout, while calcium
pyrophosphate crystals cause arthritis in pseudogout.
Some people are born with abnormally formed joints (congenital
abnormalities) that are vulnerable to mechanical wear, causing
early degeneration and loss of joint cartilage. Osteoarthritis of the
hip joints is commonly related to structural abnormalities of these
joints that had been present since birth.
Hormone disturbances, such as diabetes and growth hormone
disorders, are also associated with early cartilage wear and secondary
osteoarthritis.
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