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Osteoarthritis (OA), also known as degenerative joint disease, is the most common form of arthritis. It is a painful condition that occurs when cartilage inside a joint wears down over time. Most often, this wear results from a lifetime of use, and people get it when they reach advanced age. However, younger people may get the condition early as a result of an injury to the joint.
Osteoarthritis is different from the less common but often more serious form of arthritis known as inflammatory arthritis. This is a group of autoimmune diseases such as rheumatoid arthritis and gout. Inflammatory arthritis is caused by a problem with the immune system, and it usually causes inflammation in many joints throughout the body at the same time. Osteoarthritis, on the other hand, is usually isolated to a single joint.
Cartilage is the spongy tissue that coats the ends of bones where they meet to form joints. In joints such as elbows, knees, shoulders, ankles and knuckles, cartilage acts as a shock absorber, cushioning the bones and preventing their ends from touching during body movement. This allows a person to twist, bend, turn and have a broad range of motion. The older we get, the more our cartilage deteriorates – especially in joints that we use most frequently. When cartilage degrades, the bones are not properly cushioned and the joint becomes damaged. This results in pain, stiffness and reduced range of motion.
Osteoarthritis is most common in large weightbearing joints such as the hips or knees. With this type of arthritis, pain usually increases during activity and decreases with rest. Symptoms are often worse toward the end of the day.
Pain is the most common symptom. Pain usually occurs when the joint is being moved, rather than when it is at rest. However, in the morning or after other long periods of inactivity, some people with OA may experience a feeling of stiffness. This symptom (known as "gel phenomenon" or "gelling phenomenon") usually lasts for less than 20 minutes in the affected joint. It is caused by a temporary thickening (or "gelling") of natural fluids inside the joint.
Pain felt during movement of the joint is often accompanied by a crackling or grinding sound called "crepitus." Some people with OA may feel little or no pain for unknown reasons. The level of pain each person with OA experiences can depend on many factors including: the stage of the disease, the way a person's brain processes pain messages, cultural, gender and psychological differences.
The joints most commonly affected by osteoarthritis are:
Osteoarthritis is not associated with the following symptoms. If you have these are symptoms, you have some form of inflammatory arthritis:
There is no magic formula for avoiding joint degeneration. However, for osteoarthritis that affects the knees and hips (which are the two joints most commonly affected) maintaining an ideal weight or losing excess weight may help prevent osteoarthritis in these areas or decrease its rate of progression.
There are three key elements to getting an accurate diagnosis for osteoarthritis:
Your physician will talk with you to learn your medical history and symptoms, and then to a physical exam to assess:
When the physical exam suggests a person may have osteoarthritis, dfferent forms of imaging may be necessary to confirm the diagnosis and determine the severity of the joint degeneration.
X-rays are very helpful in diagnosing advanced osteoarthritis because the affected joint will have specific characteristics:
Confirming early onset osteoarthritis is more complicated, because the signs are far more subtle. Hospital for Special Surgery has developed special X-ray views that increase the sensitivity of conventional X-rays, allowing detection of early changes in the joint before they are evident on routine X-rays.
In some cases, X-rays alone are not sufficient to show the smaller differences associated with early onset arthritis. When this is the case, other specialized diagnostic imaging technologies are used. These include:
In some cases, when osteoarthritis is suspected, but X-rays appear normal, a special MRI process called quantitative T2 mapping can detect the subtle cartilage differences to confirm the diagnosis.
Laboratory tests are helpful for diagnosing osteoarthritis, because they are used to rule out forms of inflammatory arthritis. In other words, if you have joint pain and your lab results are normal, it would confirm a diagnosis of OA. These tests include:
When these tests return normal or negative results, this usually indicates that your arthritis is osteoarthritis. It should be noted, however, that as people age, they sometimes develop a low-level positive rheumatoid factor, ANA titer and/or elevated sedimentation rate without experiencing any obvious illness. This is why doctors do not rely on laboratory tests alone, but rather to confirm a suspected diagnosis for osteoarthritis.
Another lab test that may help confirm the diagnosis is the extraction and analysis of synovial fluid from the joint. Synovial fluid is a liquid normally found within the joints. It helps nourish and lubricate them and is usually present in only very small amounts. However, when certain forms of arthritis are present, synovial fluid will change.
In osteoarthritis, white blood cell count (“pus cells”) is usually normal and the fluid is clear (like water). Higher white cell counts should suggest inflammatory arthritis or infection, rather than osteoarthritis. In this way, extracting synovial fluid can help to confirm the diagnosis. It can also reduce pain and swelling if the fluid is contributing to inflammation.
The fluid may also be examined for the presence of uric acid crystals (seen in gout) or calcium pyrophosphate crystals (seen in pseudogout or chondrocalcinosis). The measurement of other biological markers is still experimental.
Your doctor will develop an individualized treatment program especially for you based on several factors, including:
If the osteoarthritis is not severe, it is usually first treated conservatively (nonsurgically) with physical and occupational therapy. It is wise to maintain good nutrition and a healthy weight. This will put less pressure on your joints. (Learn about the weight management program at HSS.) In the case of osteoarthritis of the knee, it is especially important to exercise and strengthen your thigh muscles, which can reduce pain and improve function.
For people with osteoarthritis, it is important to maintaining an active lifestyle and avoid becoming sedentary. Movement can help lessen pain and prevent it from getting worse. But the correct and safe types of activity vary from patient to patient. As with any treatment, getting a proper “movement prescription” requires having a pinpoint diagnosis and an understanding of each patient's unique condition.
If these conservative measures do not work, anti-inflammatory medications may be recommended. These may be:
When the conservative measures above are not enough and pain in a specific joint makes it difficult for you to move, then joint replacement surgery can restore your comfort and help you to return to normal activity. Hip replacement surgery and knee replacement surgery have become trusted treatments for restoring mobility and easing pain.
You are generally a good candidate for surgery if conservative treatment hasn't worked and you experience a significant interruption in some activity of daily life – for example, if you can't walk more than a city block or if you awaken from sleep with pain in the affected joint. In such cases, surgery should provide outstanding results, because you will become pain-free in the affected joint. The exact type of surgery you have will depend on your age, activity level, and the specific joint that is affected.
The scientists and doctors at Hospital for Special Surgery keep you informed on HSS.edu about their specific and ongoing studies and trials on all musculoskeletal conditions, treatments, and issues. Besides each Division’s research overview (linked below) the biography page of each HSS doctor and scientist links to their research, as well as their articles in noted professional journals.
You can also sign-up for the free HSS eNewsletter that brings a convenient monthly update on the latest news at the hospital right to your email inbox.
Hospital for Special Surgery’s pace-setting musculoskeletal research is organized into five main programs. And every program contributes essential knowledge to OA research:
Find more detailed information on osteoarthritis from leading experts in the articles below.