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Osteoarthritis

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Osteoarthritis is a degenerative joint disease. It involves the breakdown of joint cartilage and the underlying bone. This condition is a form of arthritis. It is believed to be the fourth leading cause of disability in the world. An estimated 240 million people worldwide have activity-limiting osteoarthritis. Unlike other types of arthritis, it only affects the joints. It does not affect internal organs.

Osteoarthritis world map - DALY - WHO2004
Osteoarthritis world map - DALY - WHO2004

The mechanism of the disease begins with subtle biochemical changes. In healthy cartilage, water content is finely balanced. Compressive forces drive water out of the cartilage. Meanwhile, osmotic pressure draws water back in. This balance relies on collagen fibers and proteoglycans. Proteoglycans create the osmotic pressure needed to hold water. During the onset of osteoarthritis, the collagen matrix becomes disorganized. There is also a decrease in proteoglycan content. This causes a net increase in water content within the cartilage. The loss of collagen outweighs the loss of proteoglycans. Eventually, the cartilage wears away and the underlying bone is affected.

As the disease progresses, several distinct structural changes occur. The ligaments within the joint may become thickened and fibrotic. The menisci, which are pads in the joint, can become damaged or wear away. In some cases, the menisci may be completely absent. New bone outgrowths called osteophytes, or bone spurs, often form on the margins of the joints. These spurs may attempt to improve the surface fit of the joint. The subchondral bone volume also increases. However, this bone becomes less mineralized.

Erosive osteoarthritis with gull-wing appearance, with seagull
Erosive osteoarthritis with gull-wing appearance, with seagull

Symptoms of osteoarthritis often progress slowly over many years. The most common symptoms are joint pain and stiffness. Stiffness is most common in the morning. It typically lasts less than thirty minutes after daily activities begin. Pain often worsens with prolonged activity and is relieved by rest. Some people experience joint swelling or a decreased range of motion. Moving an affected joint may cause a crackling noise called crepitus. This is common in the shoulder and knee joints. In smaller joints like the fingers, hard bony enlargements may form. These are called Heberden's nodes or Bouchard's nodes.

Areas affected by osteoarthritis
Areas affected by osteoarthritis

Many different factors can increase the risk of developing this condition. Mechanical stress is believed to be a primary cause. This stress can come from previous joint injuries or abnormal joint development. Obesity is a major risk factor. Osteoarthritis of the hips and knees is twice as common in people with obesity. Occupational stress also plays a role. Jobs involving heavy lifting, kneeling, or squatting increase the risk for knee and hip osteoarthritis. People who work in bent or twisted positions face higher risks for hip issues. Genetics and age are also significant factors.

Hip joint injection by anterior longitudinal approach
Hip joint injection by anterior longitudinal approach

Doctors use specific methods to diagnose osteoarthritis. They rely on a patient's medical history and clinical examinations. Medical imaging like X-rays can confirm the diagnosis. On an X-ray, doctors look for joint space narrowing. They also look for subchondral sclerosis and subchondral cyst formation. They look for the presence of osteophytes. In 1990, the American College of Rheumatology developed criteria for hand osteoarthritis. These criteria are 92% sensitive and 98% specific. This helps doctors distinguish it from other conditions like rheumatoid arthritis.

Erosive osteoarthritis with gull-wing appearance, with seagull
Erosive osteoarthritis with gull-wing appearance, with seagull

Management focuses on reducing pain and maintaining function. Lifestyle modifications are the mainstays of treatment. This includes exercise and weight loss. Losing weight can help relieve pain in the hips. Pain medications are also used. These include paracetamol and NSAIDs like ibuprofen or naproxen. Long-term opioid use is not recommended due to risks of addiction. If disability continues, joint replacement surgery may be an option. More than 90% of hip and knee replacements are due to osteoarthritis. An artificial joint typically lasts more than 20 years.

Exercise
Exercise

Osteoarthritis has a significant impact on global health. As of 2015, it affected about 237 million people. This represents roughly 3.3% of the world's population. The condition becomes more common as people age. Among those over 60, about 10% of males and 18% of females are affected. Osteoarthritis causes about 2% of years lived with disability. People with osteoarthritis of the hips or knees have a 20% increased risk of mortality. This may be due to reduced activity levels. The disease connects to broader issues of aging and physical mobility.

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File:Areas affected by osteoarthritis.gif
Areas affected by osteoarthritis.gif
File:Erosive osteoarthritis with gull-wing appearance, with seagull.jpg
Erosive osteoarthritis with gull-wing...
File:Exercise.png
Exercise.png
File:Hip joint injection by anterior longitudinal approach.jpg
Hip joint injection by anterior...
File:Osteoarthritis world map - DALY - WHO2004.svg
Osteoarthritis world map - DALY - WHO2004.svg
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