Diagnosis

During the physical exam, your doctor is likely to:

• Inspect your knee for swelling, pain, tenderness, warmth and visible bruising
• Check to see how far you can move your lower leg in different directions
• Push on or pull the joint to evaluate the integrity of the structures in your knee

Imaging tests

In some cases, your doctor might suggest tests such as:

• X-ray. Your doctor may first recommend having an X-ray, which can help detect bone fractures and degenerative joint disease.
• Computerized tomography (CT) scan. CT scanners combine X-rays taken from many different angles to create cross-sectional images of the inside of your body. CT scans can help diagnose bone problems and subtle fractures. A special kind of CT scan can accurately identify gout even when the joint is not inflamed.
• Ultrasound. This technology uses sound waves to produce real-time images of the soft tissue structures within and around your knee. Your doctor may want to move your knee into different positions during the ultrasound to check for specific problems.
• Magnetic resonance imaging (MRI). An MRI uses radio waves and a powerful magnet to create 3D images of the inside of your knee. This test is particularly useful in revealing injuries to soft tissues such as ligaments, tendons, cartilage and muscles.

Lab tests

If your doctor suspects an infection or inflammation, you're likely to have blood tests and sometimes a procedure called arthrocentesis, in which a small amount of fluid is removed from within your knee joint with a needle and sent to a laboratory for analysis.