Do You Really Need an X-Ray, CAT Scan, or MRI for Knee Pain?

Whether you’re a runner, an aspiring athlete, or just someone dealing with the aches and pains of getting older, you’ve likely at some point felt a twinge of discomfort in your knee. Considered one of the largest and most complex joints in the body, the knee is subject to a lot of wear and tear and overall stress. And while it may seem logical to explore the root cause of any discomfort with the sophisticated tech tools out there — namely x-rays and magnetic resonance imaging (MRI) — it turns out, that’s not always necessary.

“Knee pain is one of the most common sports injuries I see,” says Boston-based One Medical provider Michael Richardson, MD. “It can be very debilitating, which in turn causes a lot of anxiety for my patients and a strong desire to fix things fast. Many patients request either an MRI or x-ray when they get knee pain, but this is not always needed.”

You’ve probably heard of or experienced x-rays, CAT scans, and MRIs, but knowing each one’s unique function and purpose may help you understand why they’re not needed to diagnose and treat every case of knee pain.

X-rays are a type of radiation called electromagnetic waves that create black and white pictures of particular body parts. The varying shades of black and white indicate how much radiation each part of the body part’s tissue is absorbing; bones appear as white because they absorb the most, fat and other soft tissue appear gray because they absorb less, and air appears black because it absorbs the least (which explains why the lungs look so dark on an x-ray). Getting an x-ray is usually pretty simple and straightforward and the resulting images will allow your provider to see if there’s a fracture, joint dislocation, or some other issue affecting the bone.

Computed (Axial) Tomography (CT or CAT) scans combine the function of x-rays with computers to produce 360-degree, cross-sectional views of different body parts. These scans can show your provider what’s happening in the bones, soft tissue, and blood vessels, and can be used to detect a range of injuries and illnesses.

Unlike x-rays and CAT scans, MRIs use a strong magnetic field and radio waves to create pictures of the organs and tissues in the body. MRI scans can depict the soft tissues in your body, such as ligaments and tendons, that aren’t detectable on an x-ray. The procedure can be more intensive than an x-ray and a lot more expensive.

If you’ve been dealing with nagging pain that seemingly originated out of nowhere, imaging may not provide the enlightenment you are looking for. “Injuries that have an insidious onset, meaning came on slowly without a specific traumatic event, rarely need imaging immediately,” Richardson says. “This type of knee pain is often knee pain that comes onafter long distance running or biking. These are usually wear and tear injuries that will improve with rest, stretching, and leg strengthening exercises.”

Richardson notes that there are some specific cases that may merit more urgent imaging for non-traumatic knee pain — elderly people, very young kids, and professional athletes, for example, may need immediate attention. But for most people, strictly sticking to a self-care routine should help alleviate nagging knee pain. Don’t see a difference in your symptoms? Then it may be time to seek medical care. “If there is no improvement in the pain after six weeks of physical therapy, then your doctor may order imaging to see if there is anything odd going on with your knee,” Richardson says.

MRIs or x-rays are recommended for anyone who’s experienced a specific injury to their knee that’s resulted in pain or discomfort. “Trauma is when imaging is needed more urgently,” Richardson says. “Any injury in which the person can not bear weight on the leg or trauma that caused immediate pain, such as falling, someone or something hit you, or any other mechanism that caused extreme force to your knee.” Richardson says those types of traumatic events typically warrant an X-ray to look for broken bones or joint misalignment. If the results do notindicate any breaks, doctors typically recommend a few weeks of rest and an exercise regimen to strengthen and stretch the legs.

If, however, the pain and/or instability persists, that’s when additional imaging may be necessary. “An MRI is helpful to look for torn internal structures of the knee like your anterior cruciate ligament (ACL) and meniscus,” Richardson says. “There is rarely a need for an urgent MRI, so it is reasonable to wait a few weeks before having one done.”

Here are the most likely reasons to discuss imaging with your doctor:

• Immediate pain after some sort of trauma
• Unable to bear weight on the knee
• Knee pain that does not improve after 6 weeks of strengthening and conditioning

Not sure if you need imaging or just want to talk to a provider for more information? Visit onemedical.com to find care in your area.