Q: My left knee began to hurt two weeks ago. I am 35 and work out in the gym two to three days a week. I saw my doctor who initially was not sure what was wrong with my knee. She took X-rays, which were normal. Because the diagnosis was unclear, the doctor said I should get an MRI scan and maybe that would help delineate the problem. Why, if the X-rays are normal, do I still have pain and what does the MRI show that an X-ray does not?
A: There are four diagnostic modalities commonly used by orthopedic surgeons in helping diagnose an injury.
X-rays are helpful to diagnosis the bony anatomy such as fractures, dislocations and arthritic narrowing, however, they do not show injuries to the soft tissues.
Injuries to the cartilage, ligaments, tendons, muscles and stress fractures are best seen on MRI scans. Ultrasound can also be helpful in diagnosing tendon and muscle injuries, as well as improving the accuracy of therapeutic injections. CT scans are helpful in establishing complex fracture patterns and planning for certain joint replacement procedures.
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Since you work out in the gym regularly, you may have a tendinitis issue, a stress fracture or a meniscal cartilage tear. An MRI scan is very helpful for diagnosing these conditions.