Knee MRI Scan

An MRI is magnetic resonance imaging that shows images of a knee's structure. They allow doctors to see knee joints, including bones, cartilage, tendons, ligaments, muscles, blood vessels and internal body structures. MRIs are more detailed than an X-ray, which shows just bones.

A knee MRI is an effective non-invasive treatment that uses magnets and radio waves to capture a high quality image of the area. The images produced also show a large number of different angles of the area, increasing the likelihood of capturing the affected issue.

Unlike X-rays, an MRI doesn't use radiation. Instead, it harnesses radio waves from data that already exist in the body, meaning it won't cause chemical change or damage to tissue.

A knee MRI is performed inside a circular metal-shaped machine. Once the patient is inside, the radiologist will capture a number of images on a computer screen, each showing a thin slice of the body. From here, the doctor or radiologist can study the images to determine the issue.

If a doctor suspects an issue with a ligament or tendon in the knee, they will almost always suggest an MRI to confirm their suspicions. However, knee MRIs can detect far more than just ligament and tendon injuries or tears.

MRIs are generally ordered by a doctor when there is pain or lack of mobility with the knee, especially if an X-ray isn't able to detect the problem. If you are experiencing any of the following issues, you may require a knee MRI: knee injuries from an accident or fall; persistent knee pain that doesn't improve over time; a swollen or inflamed looking knee area; lack of mobility in the knee area; knee pain or discomfort when the knee is moved a particular way; a popping sensation or feeling in the knee; as a check-up after knee surgery; or acute knee pain that's developed suddenly.

Below are a number of conditions that an MRI can help diagnose: bone infections; tumours of the bone and surrounding soft tissues; arthritis; fluid build up in the knee; bone fractures or breaks; torn ligaments; sprains; infections; damaged or torn meniscus; problems with the knee joint; ACL tears; extra fluid in the knee; collateral ligament injury; inflammation in the knee; and degenerative joint disease.

An MRI will need to be ordered from a referring physician. So, prior to your MRI appointment, you should have already spoken about your knee issue with your GP.

Eating or drinking before a knee MRI is usually okay unless your physician advises otherwise.

Once you arrive you won't need to do anything too drastic to prepare. You'll be required to remove anything metal (like a necklace, bracelet, earrings, hairpins, piercings and hearing aids). It's important that you don't wear hairspray or makeup to the appointment, as these contain metal particles which can interfere with the MRI images. If you have a metal object inside your body, like metal pins for a broken bone or an implanted medical device, you should let the radiologist know.

When you arrive at your knee MRI appointment, you will be given a hospital gown to change into. Some variations of MRIs may require the patient to have dye administered intravenously so that the issue can be identified in the scan. From here, a technician will position you on a table so that your knee is positioned correctly for the scan. An electric machine will slide your body inside the MRI machine so that the bottom half of your body is inserted.

A knee MRI will generally take between 30 and 60 minutes, but in some cases, it can take up to two hours. Your technician will fit you with earplugs and a buzzer. When you press the buzzer you'll be able to speak to the technician who is located in a separate room.

It's very important for a patient to stay perfectly still during an MRI so that the detailed images don't get blurred. A patient shouldn't feel anything during a scan. Sometimes people feel warm during a scan, but if this happens the technician should be notified.

After the scan, patients should generally feel normal. The exception is patients who have been sedated due to claustrophobia, who will require a recovery period and will need someone to drive them home. Occasionally a patient may feel mild side effects, like slight nausea or local pain. If a patient has a rash or other allergic symptoms appear after an MRI, a doctor should be notified immediately. Results usually take around 1–2 weeks, but can be returned quicker if the condition requires urgent medical attention.

MRIs provide a very detailed image, allowing a technician to see tendons, ligaments and bone abnormalities that aren't displayed in a regular X-ray. MRIs are non-invasive and don't involve any radiation, meaning they are a very safe procedure. An MRI can show a hairline fracture that may not be evident on a normal X-ray. The detailed image from an MRI can help a doctor determine whether knee surgery is required.

A doctor will initially discuss your symptoms, pain or discomfort with you and do a physical exam of the affected area. If they suspect an issue that can be confirmed through the use of an MRI, they will refer you for the scan.

MRI tests are also often ordered after knee surgery so that healing and potential issues can be monitored. An MRI is also commonly ordered when pain is felt within the knee region but an X-ray, CT scan or other tests show inconclusive results.

A normal MRI will usually take around 30–60 minutes. In some cases where in-depth analysis is required, the scan can take up to two hours. A contrast MRI, where a contrast agent is given intravenously to provide greater image quality, can take slightly longer, but won't usually take any longer than two hours.

A patient should not be able to feel anything from the actual radio waves and magnetic process of the scan. However, they may feel minor discomfort from the positioning if their original condition was painful. If this is the case, the technician will be extremely gentle in positioning your leg so that the least amount of pain possible is caused.

No, a doctor will discuss your symptoms and conduct a physical exam first. They will only refer you for an MRI scan if they believe the scan can identify your condition.