The warning signs of osteoarthritis include steady joint pain or intermittent pain that usually worsens with activity, brief stiffness after getting out of bed, joint swelling or tenderness in one or more joints and a crunching feeling or sound of bone rubbing on bone.

No single test can diagnose osteoarthritis. Most health care professionals use a combination of the following methods to diagnose the disease and rule out other conditions:

• Clinical history. The health care professional will begin by asking you to describe your symptoms, and when and how the condition started. Be sure to provide an accurate description of pain, such as what makes it worse or better, stiffness and joint function and how they have changed over time. You should also share information on other medical conditions and any medicines you are taking.

• Physical examination. The health care professional will check your general health and examine joints that bother you, as well as your reflexes and muscle strength. He or she will observe your ability to walk, bend and carry out activities of daily living.

• X-rays and other imaging techniques. X-rays show how much joint damage has been done; they can show such things as cartilage loss, bone damage and bone spurs. But there is often a big difference between the severity of osteoarthritis that the x-ray shows and the degree of pain and disability the patient has. In addition, x-rays may not show early osteoarthritis damage (before much cartilage loss has taken place).

• Other tests. A health care professional may order blood tests to rule out other possible causes of your arthritis. Another common test includes "joint aspiration," or "arthrocentesis," during which fluid is drawn from the joint for examination. The fluid can be examined to see if it contains the crystals that cause gout or pseudogout or if it is moderately or severely inflamed, which suggests you have rheumatoid arthritis.

It is usually not difficult to tell if a patient has osteoarthritis. It is more difficult to tell if the disease is causing the patient's symptoms. Osteoarthritis is so common, especially in older people, that it may mask other conditions that are actually responsible for symptoms. A health care professional will try to find out what is causing the symptoms, ruling out other disorders and identifying conditions that may make the symptoms worse.

Not everyone with osteoarthritis feels pain. In fact, only one-third of people for whom x-rays show osteoarthritis report pain or other symptoms.

The most common way to measure pain is for a health care professional to ask you about it. For example, you may be asked to describe the level of pain you feel on a scale of one to 10. Use specific words to describe your pain-like aching, burning, stinging or throbbing to better convey what is happening. It's also important to describe if and where the pain travels (i.e., from the groin down to the knee).

Since health care professionals rely on your description of pain to help guide treatment, you may want to keep a pain diary to record your pain sensations. On a daily basis, describe the situations that cause or alter the intensity of your pain, the sensations and severity of your pain and your reactions to the pain. For example: "On Monday night, sharp pains in my knees produced by housework interfered with my sleep; on Tuesday morning, because of the pain, I had a hard time getting out bed. However, I coped with the pain by taking my medication and applying ice to my knees." The diary will give your health care professional some insight into your pain and may play a critical role in the management of your disease.