Osteoarthritis (OA) is a common type of arthritis in which there is a gradual loss of cartilage from the joints (figure 1). Common osteoarthritis symptoms include pain, stiffness, some loss of joint motion, and changes in the shape of affected joints. Although OA can affect almost any joint, it most often affects the hands, knees, hips, and spine.
Osteoarthritis is a chronic condition that gradually worsens over time; however, there are several measures that may slow its progression and control symptoms. The diagnosis of OA is the first step in ensuring the appropriate treatment of osteoarthritis.
This article reviews the symptoms and diagnostic tests that may be used for people with osteoarthritis. Treatment of OA is discussed separately. (See "Patient information: Osteoarthritis treatment (Beyond the Basics)".)
TYPES OF OSTEOARTHRITIS
There are two main types of osteoarthritis, which have differing causes.
Idiopathic osteoarthritis — Idiopathic OA has no identifiable cause. It may be localized (confined to one or two joints) or generalized (present in three or more joints).
Secondary osteoarthritis — Secondary OA is caused by an underlying condition, such as a joint injury, accumulation of calcium inside the joint, other bone and joint conditions (eg, rheumatoid arthritis), or a medical condition, such as diabetes.
OSTEOARTHRITIS RISK FACTORS
A number of factors can increase the risk of developing osteoarthritis; most people with OA have one or more of these factors (table 1).
Age — Advancing age is one of the strongest risk factors for OA. The condition rarely occurs in people younger than age 40, but at least 80 percent of people over age 55 have some x-ray evidence of the disorder. However, not all people with arthritis on an x-ray have joint pain or other joint problems.
Gender — For unknown reasons, women are between two and three times more likely than men to develop OA.
Obesity — People who are obese are at high risk of developing OA. Weight loss may reduce this risk.
Occupation — OA of the knee has been linked to certain occupations that require frequent squatting and kneeling, including cotton processing, dock work, shipyard work, and carpentry.
OA of the hip has been linked to farm work, construction work, and other activities that require heavy lifting, prolonged standing, or walking several miles each day.
Sports — The risk of OA is increased in those who participate in certain sports, including wrestling, boxing, pitching in baseball, cycling, parachuting, cricket, gymnastics, ballet dancing, soccer, and football; in contrast, running does not appear to increase the risk of OA.
The symptoms of OA usually begin after age 40 and can vary considerably from one person to another (table 1).
Pain — The main symptom of OA is joint pain that is worse with activity and is relieved by rest. In severe cases, the pain may also occur at rest or at night. The pain usually occurs near the affected joint; however, in some cases, the pain may be referred to other areas. For example, the pain of OA of the hip may actually be felt in the knee.
Joints affected by OA may be tender to the touch. The level of pain is typically constant over time. Any sudden increases in the level of pain may indicate recent injury or an underlying condition such as gout. (See "Patient information: Gout (Beyond the Basics)".)
Stiffness — Morning stiffness is a common symptom of osteoarthritis. This stiffness usually resolves within 30 minutes of rising, but it may recur throughout the day during periods of inactivity. Some people note a change in symptoms related to the weather.
Swelling (effusion) — Osteoarthritis may cause a type of joint swelling called an effusion, which results from the accumulation of excess fluid in the joint.
Crackling or grating sensation (crepitus) — Movement of a joint affected by osteoarthritis may cause a crackling or grating sensation called crepitus. This sensation likely occurs because of roughening of the normally smooth surfaces inside the joint.
Bony outgrowths (osteophytes) — Osteoarthritis often causes outgrowths of bone called osteophytes or bone spurs. These bony protuberances can be felt under the skin near joints and typically enlarge over time.
Symptoms in specific joints — Osteoarthritis does not affect all joints equally. The condition most commonly affects the fingers, knees, hips, and spine; it rarely affects the elbow, wrist, and ankle. Furthermore, it often affects joints on one side of the body differently than on the other side.
There is no single sign, symptom, or test that can diagnose OA. Instead, the diagnosis is based on a consideration of several factors, including the characteristic symptoms of osteoarthritis and the results of laboratory tests and x-rays.
Diagnostic criteria — Formal criteria are often used to diagnose osteoarthritis in specific joints.
- Osteoarthritis of the knee — The criteria for OA of the knee include the presence of knee pain plus at least three of the following characteristics:
- Age greater than 50 years
- Morning stiffness lasting less than 30 minutes
- Crackling or grating sensation (crepitus)
- Bony tenderness of the knee
- Bony enlargement of the knee
- No detectable warmth of the joint to the touch
Laboratory tests and x-rays are often used in addition to these criteria.
- Osteoarthritis of the hand — The criteria for OA of the hand include the presence of hand pain plus at least three of the following characteristics:
- Bony enlargement of at least 2 or more of 10 selected joints
- Bony enlargements of two or more distal interphalangeal (DIP) joints
- Fewer than three swollen metacarpophalangeal (MCP) joints
- Deformity of at least 1 of the 10 selected joints
Osteoarthritis of the hand can often be diagnosed on the basis of these criteria alone, and laboratory tests and x-rays may be unnecessary.
- Osteoarthritis of the hip — The diagnosis of OA of the hip relies on the results of laboratory tests and x-rays. The criteria include the presence of hip pain plus at least two of the following characteristics:
- A normal erythrocyte sedimentation rate (ESR)
- The presence of bony outgrowths (osteophytes) on x-rays
- The presence of joint space narrowing on x-rays, indicating a loss of cartilage
Laboratory tests — Laboratory tests may be recommended to help diagnose osteoarthritis by ruling out conditions with similar symptoms.
Imaging tests — X-rays are often helpful for tracking the status of osteoarthritis over time, but x-rays may appear normal during the early stages.
Other types of imaging tests, such as ultrasound and magnetic resonance imaging (MRI), may be used to detect damage to cartilage, ligaments, and tendons, which cannot be seen on x-ray.
COURSE OF OSTEOARTHRITIS
Osteoarthritis generally worsens slowly over time, although it stabilizes in some people. In those whose pain and joint stiffness worsens over time, there is usually intermittent worsening (worsening, then stabilization for a period).
Some people with osteoarthritis are able to function normally despite pain while others may have difficulty with even simple tasks as a result of pain. Exercise may help to prevent loss of strength and may decrease the chances of becoming disabled.
The treatment of osteoarthritis is discussed in a separate topic review. (See "Patient information: Osteoarthritis treatment (Beyond the Basics)".)
WHERE TO GET MORE INFORMATION
Your healthcare provider is the best source of information for questions and concerns related to your medical problem.
This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient information: Osteoarthritis (The Basics)
Patient information: Hip replacement (The Basics)
Patient information: Arthritis and exercise (The Basics)
Patient information: Meniscal tear (The Basics)
Patient information: Paget disease of bone (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient information: Osteoarthritis treatment (Beyond the Basics)
Patient information: Gout (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Clinical manifestations of osteoarthritis
Diagnosis and classification of osteoarthritis
Nonpharmacologic therapy of osteoarthritis
Patient guidelines for weight-resistance training in osteoarthritis
Initial pharmacologic therapy of osteoarthritis
Risk factors for and possible causes of osteoarthritis
Surgical therapy of osteoarthritis
Weight-resistance training in patients with osteoarthritis
The following organizations also provide reliable health information.
Patient support — There are a number of online forums where patients can find information and support from other people with similar conditions.