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Osteoarthritis of the Knee

Osteoarthritis of the knee is a disease which develops with advancing age. Its onset is considered to be associated with body weight and the habits of individuals (exercise, posture, etc.). Let's try to understand osteoarthritis of the knee correctly.

What is osteoarthritis of the knee?

Osteoarthritis of the knee is a disease characterized by articular inflammation and pain arising from injury of the cartilage of knee joints. If injured, cartilage cannot absorb the shock during motions of the knee, thus causing very intense pain. Knee pain experienced during daily life is often attributable to osteoarthritis of the knee. This disease is often seen in males and females over 50 years of age (more frequently in females). Its prevalence begins to increase gradually at ages from 40 to 49 years.

What is osteoarthritis of the knee?Once osteoarthritis of the knee develops, the patient decreases the frequency of walking due to knee pain, resulting in loss of leg muscle strength. If the muscles protecting the knee lose strength, the knee is exposed to larger burdens. To eliminate this vicious cycle, it is essential that the patient receives treatment as soon as possible. An early treatment start can control the pain and delay disease progression.

What are the symptoms?

Major symptoms are pain, swelling and difficulty walking.

- Pain during exercise

A major symptom of osteoarthritis of the knee is knee pain which occurs during knee motions. In the early stages, this pain often develops when body weight is loaded onto the knee (e.g., when the individual stands up or begins walking). At slightly advanced stages, the pain also appears during special motions such as walking upstairs/downstairs and bending knee. The pain decreases when the individual remains still, but at advanced stages the pain persists even at rest.

- Fluid pooling in the knee and swelling of the knee

Inflammation develops in the joint and fluid pools around the patella (knee cap). Fluid pooling causes swelling of the knee, occasionally resulting in pain and difficulty moving the knee.

- Disturbed knee motions (difficulty moving the knee)

The patient has difficulty bending or stretching the knee. Deviation of body position to one side is occasionally seen when the patient begins walking.

What is the cause?

The exact cause is unknown. A possible cause is injury of the cartilage which serves as a cushion for the knee joint as a result of long-term burdens on the knee.

- Aging

As the duration of burdens on the knee becomes longer, osteoarthritis of the knee is more likely to develop. It has also been reported that cartilage is more likely to be injured if hyaluronic acid (which is present within the joint and nourishes the cartilage) decreases with aging.

- Obesity

When an individual walks, the knee is exposed to a load that is more than triple the actual body weight. For example, when an individual weighing 60 kg walks, the load on the knee is about 180 kg. Thus, the load on the knee increases as body weight increases, resulting in a greater likelihood of cartilage and meniscus injuries and the onset of osteoarthritis of the knee.

- Posture

In individuals with bad posture (e.g., hunched back) while walking, the load on the knee is greater than in those assuming a normal posture when walking. Osteoarthritis of the knee is more likely to develop in such individuals. In bow-legged, the medial side of the knee is often loaded with body weight while the lateral side is loaded in baker-legged, which occasionally leads to injury of the cartilage and the onset of pain.

- Inadequate exercise

If leg muscles lose strength due to inadequate exercise, the knee is exposed to greater burdens, resulting in injury of the cartilage (serving as the cushion for knee joints) and poor absorption of shock during knee motions, leading to the onset of pain.

- Gender

This disease develops more frequently in females. The reason for the higher incidence in females is unknown, but hormone imbalances due to menopause, etc. are considered to possibly be involved.

How many patients suffer from this disease?

Prevalence of knee osteoarthritis per 100,000 people is estimated as *1,770 among male and *2,693 among female. Various factors are probably involved in the onset of this disease, but the number of patients with osteoarthritis of the knee has been increasing as the population ages. In the past, patients with osteoarthritis of the knee were unwilling to receive treatment because they thought that this disease due to aging was unlikely to resolve. In recent years, however, there has been an increase in the number of patients more actively attempting to cure their osteoarthritis of the knee and therefore visiting hospitals. This is a very common disease which can develop in any individual over age 40. Particular care is needed when there is a history of knee injury, in housewives who tend to exercise insufficiently, for individuals often engaged in desk work, those with bad posture, obese individuals and so on.
*Source: Global burden of osteoarthritis in the year 2000 by WHO