Knee Pain Imaging
X-ray – CT – MRI
X-ray is the most commonly used knee pain diagnostic test. Knee X-rays provide a wealth of information for the joint pain specialist. Key information available from these images include the amount of damage inside the knee joint, thickness of cartilage, or the presence of a fracture. Knee X-rays do have a significant limitation when it comes to the soft tissue of the knee joint, however. This type of imaging focuses on showing the bones within the knee which include the femur, tibia, fibula, and patella. An injury of the meniscus, ligaments, tendons, or other soft tissue is not visible on a knee X-ray.
A CT or CAT scan is a type of X-ray that allows a 360 degree view around the joint. As with X-rays, a knee CAT scan focuses on the hard and bony parts of the knee. It is better suited to finding fractures and arthritis and not as helpful for tears or soft tissue injuries.
MRI of the knee is a commonly performed study in cases of suspected significant soft tissue injury such as an ACL tear and meniscus injury. Surgeons planning for knee replacement with surgical removal of the knee joint will often order these images. Another type of MRI can be done with contrast dye injected into the knee which is called an MRA of the knee. A knee MRA, or knee arthrogram, may be used to more clearly see the joint surfaces and capsular structures within the knee.