Knee MRI

Knee MRI: Information and Get a Scan

Knee injuries can be as frustrating as they are debilitating. The knee is one of the most complex joints in the body. It has many important structures that need to work in unison for the joint to function correctly. Damage to one of these individual structures can result in pain. If left untreated can lead to more serious knee complications in the future.

Research has shown 23% of participants have experienced a form of knee injury, 51% of those injuries required hospitalisation. The most prevalent are ligament injuries, accounting for 40%, while 25% are miscellaneous injuries, such as contusions and strains.

Furthermore, 24% are patella related injuries, and 11% are meniscus injuries. With many possible injuries, each involving different aspects of the knee joint, it’s virtually impossible to determine the cause of knee pain through physical examination alone. An MRI scan can provide a detailed image of the knee, showing any damage, and allows physicians to make an accurate diagnosis.

Early intervention is essential to a quick and full knee recovery. An MRI scan of the knee is a painless diagnostic procedure that can help produce an accurate diagnosis to get you back on your feet. Continue as we discuss what the most common knee injuries are, and what you can expect from a knee MRI scan.

What is the Anatomy of the Knee Joint?

The knee is a synovial hinge joint made up of bones, ligaments and soft tissues that work together.

Bones

•    Patella (kneecap)

•    Femur (thigh bone)

•    Tibia (shin bone)

Ligaments

•    Anterior cruciate ligament (ACL)

•    Posterior cruciate ligament (PCL)

•    Medial collateral ligament (MCL)

•    Lateral collateral ligament (LCL)

Soft tissues

•    Meniscus

•    Joint capsule

•    Synovial membrane

•    Hyaline (articular) cartilage

The soft, fibrous tissues protect the bones from friction and shock and keep the joint lubricated. The ligaments hold the joint together and guide the hinge in the right direction: the two cruciate ligaments cross inside the joint and control front-to-back stability, while the collateral ligaments sit on either side and control side-to-side movement. Together these structures let you walk, sit and stand, and support the weight of your upper body. The knee works well only when they all work in unison. When one is damaged, it puts extra strain on the rest.

What is a Knee MRI Scan?

Doctors often use a knee MRI (magnetic resonance imaging) scan to look more closely at the structures inside the joint, particularly when pain, stiffness or swelling persists without a clear cause.

A knee MRI is a non-invasive test that uses a powerful magnetic field and radio waves to create detailed images of the inside of your knee. It does not involve radiation, which makes it a safer option than some other types of imaging such as X-rays or CT scans.

MRI is used across the body, from the brain to the spinal cord, but for the knee it produces high-quality images of the joint and surrounding soft tissue. Because it is so detailed, it can pick up problems that other methods miss, which makes it a valuable tool for diagnosing complex or long-standing knee issues.

What Does an MRI of the Knee Show?

An MRI knee scan produces detailed images of the knee joint, including,

• Tibial and Femoral Condyles (rounded end of the bone)
• Patella
• Ligaments
• Meniscus
• Joint Capsule

Unlike an X-ray, an MRI scan procedure can show the extent of damage to the fibrous tissue structures in the knee.

Early intervention is important for the recovery of knee injuries, an MRI scan increases the ability to accurately diagnose the cause of your knee pain, and begin the rehabilitation process.

What a Knee MRI Scan Can Diagnose

Doctors will often use an MRI scan to assess bone fractures that might not show up on a standard X-ray, especially when swelling or soft tissue damage suggests deeper injury.

MRI is particularly effective at showing articular cartilage, which cushions the joint and can become worn or damaged in conditions such as osteoarthritis.

While knee MRI scans are focused on the joint itself, radiologists are also trained to spot signs of more serious conditions, such as bone tumours, especially if you have unexplained knee pain or swelling.

 Here are some of the most common diagnoses of knee conditions:

• Meniscus tear: Radiologists can easily spot both partial and full meniscal tears, the cartilage that cushions your knee joint.

• ACL tear: An MRI will show whether the anterior cruciate ligament (ACL) is sprained, partially torn, or completely ruptured—information that’s vital for planning treatment for torn ligaments.

• MCL sprain or tear: The scan can reveal damage to the medial collateral ligament (MCL), helping your doctor decide whether you need rest, physiotherapy or knee surgery.

• Cartilage damage (chondromalacia): An MRI can pick up early signs of cartilage deterioration, often before you notice any symptoms.

• Osteoarthritis: MRI images reveal subtle joint changes, including thinning cartilage and swelling, which help track the progression of the condition.

• Patellar tendonitis: Doctors use MRI to detect inflammation or small tears in the tendon that connects your kneecap to your shinbone.

• Bone bruise: Unlike X-rays, MRI can reveal bone bruises—deep injuries that affect the marrow beneath the surface.

• Baker’s cyst: The scan helps identify fluid-filled cysts behind the knee, often linked with arthritis or meniscus injuries.

• PCL tear: An MRI will also reveal damage to the posterior cruciate ligament (PCL), which can impact the knee's stability.

• Osteochondritis dissecans: Radiologists can see areas where bone and cartilage may have died due to reduced blood flow.

• Joint effusion and synovitis: MRI scans clearly reveal swelling and inflammation within the joint, providing clues to the underlying cause.
  

When Should You Get a Knee MRI?

Knee pain usually means something in the joint has been injured. Often it is a simple strain that settles with rest and physiotherapy. Sometimes it is a more serious injury to a key structure, or the first sign of a degenerative condition such as osteoarthritis. Because the knee is so complex, an MRI is often the clearest way to find out which.

It may be worth arranging a knee MRI if you have:

•    Knee pain that gets worse with exercise

•    A limited range of movement

•    Sudden weakness or instability in the knee

•    A direct injury to the joint

•    Swelling or a build-up of fluid around the knee

Catching a problem early usually means simpler treatment and a faster recovery.

How Do You Read a Knee MRI Scan?

An MRI scan takes images at three different angles:

• Axial - From the top looking down
• Sagittal - From the side
• Coronal - From the front

A great way to understand how an MRI scan works is to imagine the knee as a tomato. Slices of the tomato are being cut from one side to the other; each one of those slices represents a single MRI image. Each image is a cross-section of the knee joint, as it moves from one side to the other, along one of the three angles.

A radiologist is a doctor who specialises in reading and interpreting MRI scans. They will move through the images, across one angle at a time to identify the key knee structures, looking for changes and inconsistencies in colour or shape. They will be able to identify issues such as fluid build-up, deterioration of important knee structures, or ligament tears. If an issue is identified, they can move through the set of images across the other two angles to assess the severity of the damage.

The radiologist will sign off on your scan and send it to your physician, who will discuss the results with you and advise a treatment plan if required. In some instances, there will need to be a follow-up MRI scan to evaluate the effects of the treatment, or if there is no decrease in pain.

How an MRI Scan of the Knee Works

An MRI scanner uses magnets and radio waves to stimulate protons in your body's water molecules. As those protons return to their normal state they emit signals, and the machine turns those signals into images.

Radiologists can use advanced techniques such as T1 and T2 mapping to compare healthy tissue with damaged areas. These help detect subtle abnormalities, particularly in cartilage and soft tissue.

What Equipment is Used?

Knee MRIs are usually performed on high-field machines, such as those with a 3 Tesla (3T) magnet. These produce higher-resolution images than low-field machines, which means clearer pictures and more accurate diagnoses. To improve image quality further, the radiographer places a dedicated knee coil around your leg to capture more detailed signals from the joint.

You may see scanners described as 1.5 Tesla (1.5T) or 3 Tesla (3T), which refers to the strength of the magnet. A 3T scanner gives higher resolution, but a good-quality 1.5T scan with the right sequences is usually more than enough to diagnose common knee problems such as a meniscus tear.

What Are the Risks of MRI?

MRI is considered very safe. Because it does not use ionising radiation, you can have several scans over time without increasing your health risks.

Always tell the MRI team about any metal implants or medical devices, such as a pacemaker or cochlear implant, as some are not MRI-compatible. In some cases the radiologist may recommend a contrast agent to enhance the images. If so, a gadolinium-based dye is injected into a vein in your arm or hand. Most people tolerate it well, though a small number may have an allergic reaction.

If you feel anxious or claustrophobic in enclosed spaces, mention it beforehand. You may be offered medication to help you relax, or you might prefer an open or upright MRI, which uses a more open scanner.

What do I Need to Do to Prepare for an MRI Knee Scan?

Before your scan the technician usually goes over your medical history, including any allergies. If a contrast agent is needed, MRI uses a gadolinium-based dye rather than the iodine-based contrast used for CT scans, so let the team know about any allergies. This is also the time to mention any implanted device, such as a pacemaker or defibrillator. Advances in MRI mean many people with implanted devices can be scanned safely, but the magnetic field can sometimes alter a device’s settings, so the team needs to know. Tell your radiographer if you are, or might be, pregnant. There is no known link between MRI and birth defects, but it is important to share your full medical history.

You will usually change into a hospital gown. Some clinics let you keep your own clothes if they are loose-fitting and free of metal fasteners. Guidance on eating and drinking varies by clinic, but you do not normally need to fast before a knee MRI unless told otherwise.

The Procedure Explained: What to Expect

A knee MRI usually takes around 20 to 45 minutes, depending on how many images the radiologist needs. You lie on your back on the scanner table while the team positions your knee inside the machine. You will usually go in feet first, with only your lower body inside the scanner.

Once it starts, you will hear loud tapping and knocking sounds. That is normal, and the team will offer you earplugs or headphones. Some clinics also let you listen to music.

Staying as still as possible matters. Even small movements can blur the images, and if that happens the scan may need to be repeated, which makes the appointment longer.

What Happens After a Knee MRI Scan?

When the scan finishes, you’ll be able to get up and carry on with your day as normal. If you had contrast dye, the team may recommend drinking more water to help flush it out.

A radiologist will then review your images and write a detailed report. Your doctor will go over the results with you and explain the next steps, whether that means physiotherapy, further tests, or a referral to a specialist.

How Long Should an MRI Knee Scan Take?

An MRI scan of your knee should take on average 10–30 minutes. You will be instructed to wear a hospital gown or loose-fitting clothing without metal clasps or zippers. Certain types of metal can interfere with the MRI machine, causing blurred images. If this occurs the scan will need to be repeated.

It is important to stay extremely still during this procedure. Sudden movements during the scan can also produce blurred images. If this happens, the scan will need to be repeated causing a longer MRI procedure.

How Much Does a Knee MRI cost?

Prices for knee MRI scans can vary based on your location, the hospital you choose, and whether or not you need a separate appointment with a consultant to get a referral.

We're the UK's largest imaging network with over 200 scanning centres to choose from, with complete pricing transparency that includes a pre-scan consultation, your referral, your scan, copies of your report and images, and a post-scan follow-up call. Scan.com makes it easier to compare prices across all of the options near you with no hidden costs, with knee MRI scan costs starting from just £295.

The benefit of choosing a private MRI knee scan is reduced wait times. Currently, to receive a non-urgent MRI through the NHS, the wait time can be up to 18 weeks or more. Our private MRI clinics offer a quick alternative, most appointments can be made within two weeks. Knee injuries can often begin as a small issue, growing more severe and painful over time. It’s important to identify the issue quickly to intervene with the appropriate medical treatment.

Getting the Results

Many imaging centres aim to deliver results within a few days. However, timelines can vary depending on the complexity of your scan or the urgency of your referring doctor's need for the results.

If your results are urgent, your GP or specialist can often request a faster turnaround.

Treatment and Next Steps

An MRI is a diagnostic step rather than a treatment, but it usually points clearly to what should happen next. What that looks like depends on the finding:

•    Mild sprains and minor cartilage wear are often managed conservatively with rest, physiotherapy and time.

•    A meniscus tear may settle with physiotherapy, or need keyhole (arthroscopic) surgery if it is causing locking or persistent pain.

•    A fully ruptured ACL often needs reconstruction, particularly for people who are active or play sport.

•    Advanced osteoarthritis may be managed with physiotherapy, injections or, in time, a knee replacement.

The value of the scan is that it gets you onto the right pathway quickly rather than guessing. Your report and images can be shared with your GP, a physiotherapist or a specialist, and a post-scan consultation is available if you want to talk the results through.

Get a Knee MRI Scan

If you have knee pain, swelling, or mobility issues that aren’t improving, you can book a private knee MRI scan today. If you’re unsure whether an MRI is suitable for you, one of our expert clinicians is available for a personalised consultation. They can discuss your symptoms and concerns and help you decide what to do next. 

FAQs

Does your whole body go in for a knee MRI?

Usually not. The scanner only needs to cover the lower half of your body, though this can vary with the machine used.

What should I wear for a knee MRI?

Loose, metal-free clothing works well, but most people are asked to change into a gown for safety.

Can you have an MRI with a knee replacement?

Yes. Most modern metal knee replacements are made from non-magnetic materials that can be scanned safely. The metal can affect image quality, so your radiology team will check the implant material and adjust the settings to get the best results.

How long does it take to get results?

Most people receive their results within a few working days, though this can vary.

How long should I wait after a knee injury before having an MRI?

It depends on your symptoms. If pain and swelling continue beyond a few days, or your doctor suspects serious damage, you may be referred for an MRI sooner.

Do I need a GP referral for a private knee MRI?

No. With Scan.com you do not need a GP referral. A pre-scan consultation with a clinician is included, and they arrange the referral for you if a scan is appropriate.

Can I drive home after a knee MRI?

Yes. A standard knee MRI does not affect your ability to drive, so you can drive yourself home and return to normal activities straight away. The exception is if you are given medication to help with anxiety or claustrophobia, in which case you should arrange for someone else to drive.

What can a knee MRI show that an X-ray cannot?

An X-ray shows bone but not soft tissue. An MRI shows ligaments, cartilage, the meniscus and even bruising within the bone marrow, so it can diagnose problems an X-ray would miss.

What happens if the scan finds something?

Your report goes to your referring clinician, who will explain the findings and recommended next steps. Depending on what is found, that might be physiotherapy, further tests or a referral to a specialist. A post-scan consultation is available if you would like to discuss the results.

References

1. https://bjsm.bmj.com/content/34/3/227.2
2. https://www.innerbody.com/image/skel16.html
3. https://pubmed.ncbi.nlm.nih.gov/22506941/
4. https://josr-online.biomedcentral.com/articles/10.1186/s13018-020-01638-1
5. https://www.radiologyinfo.org/en/info/kneemr
6. https://regenexx.com/blog/read-knee-mri/#gref
7. https://medlineplus.gov/ency/article/007361.htm