Xrays vs. MRI: Do I really need an xray?

Note: This is the first post in a three-part series discussing the use of xray and MRI in an orthopedic sports medicine practice. There seems to be a good deal of confusion among the general public and physicians as well about when to order xrays and/or an MRI. I expect that this series and the underlying premise (xrays are very helpful and should be routinely ordered, while MRIs are utilized far too frequently) will not be a universally accepted opinion. I would like for the reader to understand the basic concept of each test in order to understand why their physician orders tests to evaluate sports injuries.

One of the questions I’ve frequently get in the office when I’m evaluating a patient for a new sports injuries is whether or not I need to order an xray. To answer that I need to explain why many people don’t feel like they are necessary. As you may or may not know, xrays just show bones. They don’t show soft tissue structures like the tendons, ligaments, meniscus in the knee, muscles, cartilage, etc. Many people correctly assume that their injuries are soft tissue in nature, such as a rotator cuff tear, ligament tear, or meniscus tear. While they may be right, we often request that patients have an xray taken either during or prior to their orthopaedic office visit. Sometimes patients question the need for xrays as they don’t feel that there is a broken bone and therefore would have xrays that would not show anything abnormal. Unfortunately, xrays are necessary to the orthopedic surgeon for making the correct diagnosis.

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Three reasons an X-ray can be important

Xrays are important for at least three reasons. First, there may be findings on the x-rays that may make more advanced study such as an MRI unnecessary. One of the best examples I can give of that is obtaining knee xrays when evaluating for a possible tear of the ACL. While it’s true that the anterior cruciate ligament is only seen on an MRI and not on an xray, secondary bony findings can be seen. For instance, if there’s a small piece of bone pulled off the lateral tibial plateau (the top of the shin bone towards the outside of the knee), that finding implies that the ACL is torn and very likely makes an MRI unnecessary.

Another reason that we order xrays is that they occasionally show findings that we weren’t expecting but that are important. Without sounding too alarmist, I can count numerous examples both from my practice and other colleague’s examples where tumors and other serious findings were found on xrays when these were not the expected findings. For instance, a high-school female athlete could present for evaluation of a snapping sensation in the front of her hip. This would likely be a tendon snapping across the front of the hip and likely of no significance. Despite the fact that I would not expect the xrays to show any pathology because a tendon does not show up on an xray, I would order them to make sure there were no other findings. As I said earlier, I can unfortunately imagine a scenario where she could have a lesion in the femur at the hip joint, necessitating referral to an orthopaedic oncologist. The xrays hopefully would help to catch it early, potentially preventing a much more serious problem.

Finally, xrays can show us the status of the joint involved. For instance, in people with meniscal tears, especially adult athletes, it can be helpful to know if there are ny coinciding degenerative changes in the knee. The xrays might show joint space narrowing and bone spurs that would imply that there are advanced degenerative changes that might affect not only the diagnosis but treatment outcome.

Ask your doctor if an xray is necessary

If there’s ever a question of whether or not an xray is necessary, you should always ask either the office staff or the doctor himself to determine what studies are necessary and important.

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Read all three part of this series.
X-rays vs. MRI’s, Part 2 of 3: Do I need an MRI?
X-rays vs. MRI’s, Part 3 of 3: Are primary-care providers ordering too many MRI’s?

Joint space narrowing
Note the bone-on-bone joint space narrowing of the left knee.