How to diagnose knee pain?

The cause of knee pain can usually be identified by a thorough review of symptoms and a physical examination. In some cases, x-rays and other tests may be helpful.  For example:

•    Symptoms – Knee pain accompanied by locking – when the knee is temporarily stuck in one position – may be due to torn cartilage. Use-related symptoms that worsen with higher levels of activity are typical of osteoarthritis (also called degenerative joint disease). If symptoms of knee pain or stiffness are much worse in the morning and take more than an hour to improve, rheumatoid arthritis or another cause of knee inflammation may be suspected. Sudden pain and swelling are more suggestive of gout, pseudogout or infection.
•    Physical examination – If the ability of the knee to fully flex or extend is limited and there is a grinding sensation appreciated during movement, osteoarthritis is likely. Pain with pressure on the kneecap can suggest patellofemoral syndrome. A collection of fluid in front of kneecap suggests prepatellar bursitis while pain to pressure just below the kneecap may indicate tendinitis. Instability of the knee during examination suggests a ligament problem.
•    X-rays – Imaging of the knee by standard x-rays can demonstrate fracture, different types of arthritis, fluid in the knee, or abnormal calcium deposits.
Additional testing, such as MRI, may be needed to determine whether the cause of knee pain may be related to torn cartilage or a torn ligament. If there is fluid present in the knee, removing a sample of the fluid and testing it in the lab can be quite helpful in diagnosing the cause of knee pain.