Yes, you can have an MRI with most modern knee replacements, but you must tell the MRI facility about your implant first
Most knee replacements made in the last 15 to 20 years are MRI-safe or MRI-conditional, meaning an MRI machine will not damage them and they will not interfere with the scan. The catch is that the facility running the MRI needs to know you have an implant, and they need to know the specific model and manufacturer. If you cannot provide that information, they may refuse to scan you or delay the procedure while they track down your surgeon's records.
Older knee replacements — particularly those implanted before 2005 — may contain materials that react to the magnetic field. Even if your implant is safe, the MRI technician has to verify it before you enter the machine. This verification step takes time but is standard practice and protects you.
Key Takeaways
- Most knee replacements installed in the past 15 to 20 years are safe for MRI, but you must inform the facility before your appointment.
- You will need the name of your implant manufacturer and the model number, which your surgeon's office can provide if you do not have it.
- The MRI facility will check your implant against their safety database before allowing you into the machine.
- Older implants or those with ferromagnetic components may require alternative imaging methods such as CT scan or ultrasound.
- Always bring your implant card or documentation to every medical appointment, including the MRI facility.
How to learn about your specific knee replacement is MRI-safe
Your surgeon should have given you an implant card or documentation when your knee replacement was placed. This card lists the manufacturer and model number. If you still have it, bring it to your MRI appointment. If you have lost it, call your surgeon's office and ask for a copy — they keep records of every implant they place and can usually fax or email the information within one business day.
If you do not know who your surgeon was or cannot reach their office, contact the hospital or surgical center where the procedure took place. The facility has a record of your surgery and the implant used. You can also check any discharge paperwork from your surgery; it often includes the implant details.
Once you have the manufacturer and model number, the MRI facility will look it up in their safety database. Most modern implants — including those from Stryker, Zimmer Biomet, Smith & Nephew, and DePuy Synthes — are listed as safe. The facility will confirm this before your scan.
What happens during an MRI with a knee replacement
The MRI technician will ask you to remove all metal objects and change into a hospital gown. You will lie on a table that slides into a large tube-shaped machine. The machine creates a strong magnetic field and takes detailed pictures of the area being scanned. The process is painless but loud — you will hear knocking and buzzing sounds.
If your knee replacement is MRI-safe, the implant itself will not heat up, move, or distort the images. However, the metal in the implant can create a small area of blurring or artifact around the knee on the scan. This is normal and does not affect the quality of images from other parts of your body. If the scan is focused on your knee, the radiologist will account for this artifact when reading the images.
The entire scan usually takes 30 to 60 minutes. You must stay still during this time. If you are claustrophobic or anxious, tell the technician before you enter the machine — they can offer headphones, a panic button, or other accommodations.
MRI-conditional implants and what that means
Some knee replacements are labeled MRI-conditional rather than fully MRI-safe. This means the implant is safe for MRI, but only under specific conditions. The conditions might include a maximum magnetic field strength (usually 1.5 Tesla or 3 Tesla), a limit on how quickly the magnetic field changes, or a requirement that the implant be scanned at a certain distance from the machine's center.
The MRI facility will know these conditions and will adjust their machine settings to match them. You do not have to do anything — the technician handles the technical details. The important thing is that you provide your implant information so the facility can check whether their machine meets those conditions.
If your implant is conditional and the facility's machine does not meet the requirements, they will tell you before the scan. In that case, you may be offered an alternative imaging method or referred to a different facility with compatible equipment.
What to do if your implant is not MRI-safe
If your knee replacement is older or contains ferromagnetic materials, it may not be safe for MRI. This is rare with modern implants, but it does happen. If your implant is not MRI-safe, the facility will not scan you with an MRI machine.
Instead, ask your doctor about alternative imaging options. A CT scan (computed tomography) produces detailed cross-sectional images and is safe with most knee replacements. An ultrasound uses sound waves instead of radiation or magnetism and is also safe. X-rays are another option, though they provide less detail than MRI or CT. Your doctor will recommend the best alternative based on what they need to see.
If you need an MRI for a medical reason and your implant is not safe, talk to your surgeon about whether the implant can be replaced with a newer, MRI-safe model. This is a significant decision and not always necessary, but it is an option if imaging is critical to your care.
Preparing for your MRI appointment with a knee replacement
Call the MRI facility at least one week before your appointment and tell them you have a knee replacement. Provide the manufacturer and model number if you have it. If you do not have this information yet, get it from your surgeon's office before you call.
Bring your implant card or documentation to the appointment. Arrive 15 minutes early to allow time for the facility to verify your implant in their system. Wear comfortable, loose clothing with no metal zippers, buttons, or snaps — you will change into a gown anyway, but it speeds up the process.
Tell the technician if you have any other metal implants, such as a pacemaker, metal pins in your spine, or metal fragments in your eyes. These can affect whether you can have an MRI at all. Also mention any tattoos with metallic ink, though most modern tattoo inks are safe.
Common reasons for MRI after knee replacement
Doctors order MRI scans after knee replacement for several reasons. If you have persistent pain, swelling, or instability in the knee, an MRI can show whether the implant is positioned correctly, whether there is fluid buildup, or whether soft tissues like ligaments or cartilage are damaged. An MRI can also detect infection or loosening of the implant, though these are uncommon.
Sometimes an MRI is ordered for a problem unrelated to the knee — for example, a back injury or a brain concern. In these cases, your knee replacement is not the focus of the scan, but you still need to disclose it so the facility can adjust their settings if needed.
If your doctor orders an MRI and you are unsure whether it is safe with your implant, ask your surgeon before the appointment. Do not skip the MRI out of worry — your surgeon can confirm whether it is safe and can provide the implant details the facility needs.
Frequently Asked Questions
Will the MRI damage my knee replacement?
No. If your implant is MRI-safe or MRI-conditional and the facility follows the correct settings, the MRI will not damage it. The magnetic field does not harm modern implant materials, and the implant will not move or heat up. The facility verifies your implant before scanning to may support safety.
What if I cannot find my implant information?
Call your surgeon's office and ask for a copy of your implant card or surgical records. If you do not know your surgeon's name, contact the hospital or surgical center where your knee replacement was done. They have records of every implant placed there. You can also ask the MRI facility to contact your surgeon directly — many facilities do this routinely.
Can I have an MRI if my implant is older than 20 years?
It depends on the specific implant. Older implants may contain materials that are not MRI-safe. The facility will check your implant model in their safety database. If it is not safe, they will offer alternative imaging such as CT scan or ultrasound. Do not assume an old implant is unsafe — let the facility verify it.
Will the MRI images be blurry around my knee?
There may be a small area of blurring or artifact around the implant itself, which is normal and expected. If the scan is focused on your knee, the radiologist will account for this when reading the images. If the scan is of another body part, the artifact will not affect those images.
Do I need to remove my knee replacement before an MRI?
No. Your knee replacement is permanently attached to your bone and cannot be removed without surgery. You do not need to do anything to prepare the implant itself — just inform the facility that you have it and provide the manufacturer and model information.