Osteoarthritis (Degenerative Joint Disease)

What is Osteoarthritis?
Commonly affected joints
Types of Osteoarthritis
Osteoarthritis causes and risk factors

What is Osteoarthritis?

Osteoarthritis (also called degenerative joint disease or osteoarthrosis) is the most common type of arthritis affecting about 20 million people in the United States. Osteoarthritis occurs more frequently in middle-aged and older people. Before age 45, osteoarthritis occurs more frequently in males. After age 55 years, it occurs more frequently in females.

Osteoarthritis is a disease characterized by degeneration of cartilage and its underlying bone within a joint as well as bony overgrowth. Cartilage is the slippery tissue that covers the ends of bones in a joint and serves as a "cushion" between the bones of the joint. Healthy cartilage allows bones to glide over one another. It also absorbs energy from the shock of physical movement. In osteoarthritis, the surface layer of cartilage breaks down and wears away. This allows bones under the cartilage to rub together, causing pain, swelling, and loss of motion of the joint. Over time, the joint may lose its normal shape. Osteoarthritis can involve a number of joints, but unlike some other forms of arthritis, id does not affect internal organs.

The symptoms of osteoarthritis can vary from person to person. Some of the more common symptoms include: stiffness, pain, muscle weakness.

Commonly affected joints

Osteoarthritis most commonly occurs in the weight bearing joints of the hips, knees and spine. It can also affect the fingers, neck and large toe. It rarely affects other joints unless prior injury or excessive stress is involved.

Knees. The knee is the most commonly affected joint. People often complain of pain with walking and, over time, limit their walking distance. The knees can develop a bony prominence and a crunching sound with movement.
Hands (usually the end finger joints). Hand osteoarthritis is very common, especially in women. Most women will experience this type of arthritis at some point in their life. Bony overgrowth occurs at the joints of the fingers. These growths, which are called Hebernon's and Bouchard's nodes, occur in the sets of joints closest to the fingertips. Pain, swelling and redness occur during the bony deposition.
Spine (in the neck or lower back). The cervical (neck) and lumber (lower back) spine is composed of vertebral bodies that are connected by joints and have cushioning discs between levels. Over time, these joints are subject to wear and tear, which can cause osteoarthritis and disc degeneration. This can lead to pain in the neck, and the upper and lower back.
Hips. Older people are most at risk to develop hip osteoarthritis. The hip is one of the major weight bearing joints of the body. In younger patients, hip osteoarthritis occurs because the individual has an imperfect ball and socket joint. In older patients, it is the result of wear and tear over time. Hip arthritis causes groin pain and knee pain.

Types of Osteoarthritis

There are two distinct types of osteoarthritis: primary and secondary.

Primary osteoarthritis is associated with aging and is thought of as wear and tear osteoarthritis. The older you are, the more likely it is that you will have some degree of primary arthritis.
Secondary osteoarthritis occurs in joints that have sustained injuries, experienced infections or fractures. Obesity can also cause secondary osteoarthritis due to the added pressure on weight bearing joints. Secondary osteoarthritis can also occur as the result of another type of arthritis, such as rheumatoid.

Causes and risk factors

Osteoarthritis results from chemical changes in the cartilage that cause it to break down faster than it can be produced. The exact causes of osteoarthritis are unknown, but are believed to be a result of both mechanical and molecular events in the affected joint.

Aging process. The risk of osteoarthritis increases with age. Since “wear and tear” does play a part in the development of osteoarthritis, the older you are, the more you have used your joints. Although age is an important risk factor, it doesn’t mean that osteoarthritis is inevitable.
Overweight and Obesity. Increased body weight is a serious factor in the development of osteoarthritis, particularly in the knees and hips. In the Framingham Osteoarthritis Study, the risk of osteoarthritis of the knees in women increased 40% for each 10-pound weight gain. Weight loss can decrease the symptoms of knee osteoarthritis or the chances of developing those symptoms.
Joint Injury and Overuse. Injuries contribute to the development of osteoarthritis. Athletes and people who have jobs that require doing repetitive motion, such as landscaping, typing or machine operating, have a higher risk of developing osteoarthritis due to injury and increase stress on certain joints.
Genetics or Heredity. Genetics appear to play an important role in the development of osteoarthritis. Inherited abnormalities of the bones that affect the shape or stability of the joints can lead to osteoarthritis. People born with an abnormality of the spine (such as scoliosis or curvature of the spine) are more likely to develop osteoarthritis of the spine.
Muscle weakness. Muscle weakness increases the chances of developing osteoarthritis. Studies of the knee muscles not only show that weakness of the muscles surrounding the knee can lead to osteoarthritis, but that strengthening exercises for thigh muscles are important in reducing the risk.
Other Diseases and Types of Arthritis. People with rheumatoid arthritis tend to have a greater chance of developing osteoarthritis. Also, hemochromotosis, or having too much iron, can damage cartilage to the point of chronic deterioration. Acromegaly, or excess growth hormone, also has adverse affects on the bones and joints and can lead to osteoarthritis.
Gender. Before age 45, osteoarthritis occurs more frequently in males. After age 55, it develops more often in females. Some studies suggest that the decline in native estrogen after menopause might play a role in women's greater risk, particularly since estrogen replacement therapy is associated with decreased risk.
Joint infections. Although it is unusual, joints can be infected by bacteria, viruses, fungi, and mycobacteria, all of which can penetrate joint spaces. This causes acute damage and paves the way for chronic damage and future osteoarthritis. Some of the most well known microbes that infect joints include the bacteria that cause Lyme disease and gonorrhea.
Diet. Studies have shown that high levels of vitamin C and vitamin D in the diet may be beneficial in osteoarthritis. In one study, evidence of continuing joint damage was reduced three-fold in those people with the highest dietary intake of vitamins C and D.

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