Diagnosis

Your doctor is likely to start with a detailed history and physical examination. After that you likely will need tests to determine the underlying problem that is causing your swollen knee.

Imaging tests

Imaging tests can help show where the problem is located. Options include:

• X-ray. An X-ray can rule out broken or dislocated bones, and determine if you have arthritis.
• Ultrasound. This test can check for arthritis or disorders affecting the tendons or ligaments.
• MRI. This test can detect tendon, ligament and soft tissue injuries that aren't visible on X-rays.

Joint aspiration (arthrocentesis)

Your doctor withdraws fluid from inside your knee to check for the presence of:

• Blood, which may stem from injuries or bleeding disorders
• Bacteria, which may be causing an infection
• Crystals common to gout or pseudogout