Osteoarthritis: Risk Factors and Symptoms

Osteoarthritis, or OA, is the most common form of arthritis. This chronic disease affects about 80% of Canadians by the time they reach the age of 75. In the U.S. nearly 21 million people over the age of 45 have OA. It has been estimated that 41 million Americans 65 years and over will have OA by the year 2030.

Osteoarthritis is a non inflammatory disease of the joints that results in a breakdown of cartilage over time. You’ve already learned that cartilage cushions the end of the bones and acts as a shock absorber. In a healthy person, cartilage breaks down and then restores itself. In the person with OA, cartilage breaks down much faster than it can be repaired. When cartilage is gone, bone surfaces grate together causing pain. Pain is also felt in the muscles and supporting tissues. Bony spurs grow from the bone edges, leading to changes in the shape of the bone and joint, and synovial fluid increases.

WHAT ARE THE RISK FACTORS FOR OA?

The exact cause of OA is not known. Several factors, however, called “risk factors”, make it more likely that someone will get OA. These factors include:

Age
80% of people over the age of 65 have some degree of OA that can be seen on an x-ray. As the number of older adults increase, we can expect that OA will become more common over time.

Obesity
Obese persons are at increased risk for OA, mainly OA of the knees. Standing or walking exerts a pressure of up to 6 times a person’s body weight on the knees and up to 3 times the body weight on the hips. So you can see why obesity can lead to joint problems.

Genetics
OA is not thought to be a genetic disease, although there is an increased risk for those whose parents had the disease.

Injury or trauma
An example would be an injury caused by lifting over a period of time.

Lack of exercise
Regular exercise lowers the risk of OA in several ways. It helps strengthen supporting muscles, tendons and ligaments, it promotes cartilage growth and it assists in weight control.

WHAT ARE THE SYMPTOMS OF OA?

OA can be present for many years before symptoms appear. The first symptom of OA is often the slow onset of aching joint pain. OA most often affects joints in the knees, hips, spine, ankles, and hands. Pain often occurs with activity and is relieved by rest. Joint stiffness occurs after periods of inactivity. Stiffness improves as the person moves around.

DIAGNOSING OA

There is no one test for OA. The diagnosis is based upon the following:

History
The history includes the symptoms. There may be local pain and stiffness with little or no swelling. The affected joints are usually weight-bearing ones as well as joints in the spine and in the hand. The pain may occur with activity but improve with rest.

Physical exam
Some joints may be enlarged. Limited range of motion may be present. Crepitus is a grating sound and sensation caused by bones rubbing together. It may be heard and felt upon movement of one or more affected joints. Advanced disease may cause some joints to “lock” as the person walks. The disease can also result in bony growths in the hands.

X-ray findings
X-rays may show bony spurs and a narrowed joint space due to wearing away of cartilage.

Lab findings
A lab test can be done to rule out other types of arthritis such as RA and gout.