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Child Orthopedics
Spine - Cervical
Spine - Lumbar
Spine - Thoracic

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How do I know when I should request an MRI for a knee problem? The surgeon thinks I have a meniscal tear that requires surgery. I'm not so sure. Would an MRI give any more information than we already have?

In the case of the meniscus, a C- or horseshoe-shaped piece of cartilage in the knee, the McMurray test is used most often to diagnose posterior (along the back of the knee joint) meniscal tears. There are other meniscal tests that can be done for tears in other parts of the joint but the posterior tears are the most common. There are two McMurray tests: the standard or conventional McMurray and the paradoxical McMurray. Both tests are performed in the same way. The knee is bent; the examiner holds the heel and twists the lower leg in and out. If there is a torn or loose meniscus, there will be a painful, snapping or clicking sensation as the movement shifts or traps the meniscal flap or fragment between the tibia (lower leg bone) and the femur (thigh bone). The results are what make the test conventional or paradoxical. For example, the test is considered "paradoxical" when the leg is rotated internally (inward) and the medial side of the knee (side closest to the other leg) clicks. There can also be a paradoxical McMurray when the leg is rotated externally (outward) and the clicking occurs in the lateral compartment (or side) of the knee. Lateral refers to the side of the knee away from the other knee. The results just described are considered paradoxical, meaning the opposite of what is expected. In the conventional test, the clicking occurs on the opposite side of the knee from the rotation. When the leg is rotated inward, the clicking occurs on the outside of the knee. When the knee is rotated outward, the clicking occurs on the inside of the knee. An MRI should be ordered when the paradoxical McMurray test is negative but the patient has pain and other clues pointing to a meniscus problem. A positive paradoxical test is a sign that there is a large meniscal tear -- long enough to shift the loose or torn meniscus during the test. But a positive paradoxical McMurray test does not mean the patient should have surgery immediately. The surgeon must evaluate the patient history and clinical findings and find out the patient's goals and activity level. If you are having doubts about the proposed treatment, it may be a good idea to either get a second opinion or go back to your surgeon with your questions and concerns. Some people do both and there's nothing wrong with that plan of action. You must be satisfied that the diagnosis is accurate and the planned treatment is the best option for your specific situation.


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