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When should I get an MRI of the knee? It depends whether you have arthritis, ACL or meniscus tear.

When should I get an MRI of the knee? It depends whether you have arthritis, ACL or meniscus tear. 150 150 Team ATR1

Magnetic resonance imaging play a very important role in helping us help you get rid of your knee pain. But when should you get an MRI of the knee? Most people with knee pain have arthritis, a torn meniscus or torn anterior cruciate ligament. Arthritis shows up on a plain x-ray; but it takes MRI to know if you have a torn ACL or meniscus. If your problem is serious you need an MRI and doctor visit emergently, which means today. But for most people MRI can wait; how long depends on whether your are over 55, and what your x-ray shows.

In order to figure out if you need an MRI scan, a little background is in order. The meniscus is a horseshoe shaped piece of cartilage between the leg and thigh bones. The meniscus both cushions (absorbs) shocks in the knee, and prevents the bones from touching and grinding against one another as the knee moves. A torn meniscus causes clicking, popping, and locking of the knee. Because the meniscus is made of cartilage, and cartilage does not show up on x-ray, a torn meniscus will not show up on x-ray. Luckily, however, a torn meniscus lights up and is shown clearly on MRI.

The anterior cruciate ligament (ACL) supports the knee by preventing the thigh bone from sliding forward on the leg bone. The ACL can be torn suddenly while playing a sport, but is sometimes torn by gradual wear and tear. When the ACL is torn in a sports injury you feel a pop and the knee gives out making it hard to walk. When the ACL tears more gradually there is often no specific moment or pop; knee pain and a sense that your knee can’t hold your weight comes on gradually. A ligament, like cartilage, does not show up on x-ray; therefore a torn ACL is best seen on MRI and does not show up on x-ray.

Arthritis is the result of inflammation on the knee. This can occur due to trauma, gradual degeneration of the smooth cartilage in the knee joint (osteoarthritis), or due to an underling problem (rheumatoid arthritis). Arthritis causes thinning of the cartilage in the joint, rough surfaces, and can even result in loose bodies of cartilage floating in the fluid of the knee joint. All of these changes in the knee due to arthritis can be seen on MRI.

How do you know if your knee problem is serious? A knee problem is serious if you have any red flags (sudden onset of pain so severe you can’t walk; deformity of the knee; a red, hot, swollen knee; history of cancer; unexplained weight loss; blood in your urine, stool, or vomit) then the problem could be serious and you need an urgent evaluation. The necessary urgent evaluation includes blood work (serum WBC, ESR, CRP), examination by a doctor experienced in serious knee conditions, x-ray, and likely MRI imaging. As you can tell, this type of urgent workup is most often done in a hospital emergency room. Fortunately, knee problems are rarely life threatening, and the vast majority of the time the evaluation is done outside the hospital.

Back to the question of at hand — assuming you have no red flags— then how do you know if you need an MRI? Since most issues get better on their own without medical treatment, then if you are within the first 3 weeks after injury then an MRI can wait. If your knee pain is not getting better on it’s own after three weeks you should see a doctor. She will likely perform a physical examination, x-ray, and blood tests for infection. The results of these tests will determine whether or not you need an MRI.

If you are over 55, x-rays show signs of arthritis, and the physical exam is not suspicious for a torn meniscus or ACL, then you likely have arthritis and should start rehabilitation. If your arthritis is not better after three weeks of rehab then you should try a hyaluronic acid (synvisc, euflexxa, hyalgan, monovisc, orthovisc, supartz) injection. These injections help lubricate the synovial fluid of the knee, and often relieve pain for weeks to months. If you are still severely impaired from advanced arthritis of the knee despite HA injection then its time to see a surgeon for possible minimally invasive robotic assisted partial or total knee replacement.

On the other hand, if the x-ray does not show arthritis, you’re under 55, or your physical exam suggests a torn ACL or meniscus, then you need an MRI right away.

Look, we know this is complicated. What did you expect? We’re dealing with a human body here. If you have no idea what to do then contact us. One of our trained Patient Solutions Advocates will connect you with the care you need.