Imaging tests can allow your doctor to see inside your joint painlessly. The most common imaging tests to diagnose knee problems are:

X-ray (radiography). A standard X-ray is a simple test in which an X-ray beam (a form of electromagnetic radiation) is passed through the knee to create a two-dimensional picture of the bones that form the joint. Your doctor can use X-rays to view:
• joint alignment. Problems with alignment can cause or worsen arthritis-related changes in the joint.
• joint space. Narrowing of the space between the two bones, which are normally covered by cartilage, can be a sign of arthritis and its severity.
• bone spurs. Bony overgrowths at the joint are a sign of osteoarthritis.
• fractures.

Learn how a new way to read X-rays may predict osteoarthritis.

Computerized axial tomography (CAT) scan. Also called  a computed tomography (or CT) scan, this noninvasive test combines X-ray equipment with sophisticated computers to produce multiple images of the knee. The computer can combine the individual images to create a three-dimensional view of the knee. CT scans show soft tissues such as ligaments and muscles more clearly than traditional X-rays, so they are more useful for diagnosing certain knee problems, such as a torn meniscus.

Magnetic resonance imaging (MRI).  This procedure uses a strong magnet linked to a computer to create a picture of the knee joint in black and white and shades of gray. Because an MRI shows the soft tissues as well as the bones, it is particularly useful for diagnosing injuries to the cartilage, tendons, ligaments tendons and menisci, as well as areas of swelling.

Learn how new MRI technology may enable early osteoarthritis diagnosis.