Yes, you can have an MRI with a knee replacement, but you need to tell the imaging center beforehand

Most modern knee replacements are MRI-safe, meaning the magnetic field will not damage the implant or cause it to move. However, the metal components in your knee replacement can create image artifacts — dark streaks or blurry areas — that may make it harder for radiologists to see soft tissue clearly. The imaging center must know you have a replacement before your scan so they can adjust settings, choose the right coil, and position you correctly.

The safety and image quality depend on what your knee replacement is made of and how old it is. Replacements from the 1980s and earlier may contain materials that are not MRI-safe, though this is rare. Your surgeon's records or the implant card you received after surgery will list the exact model and materials. Bring this card or paperwork to your MRI appointment — the technologist will check it against their safety database before you enter the machine.

Key Takeaways

  • Tell the imaging center you have a knee replacement when you schedule your MRI, not when you arrive.
  • Bring your implant card or surgical paperwork so the technologist can verify the exact model and materials before the scan.
  • Metal in the replacement creates image artifacts that may blur soft tissue, so the technologist may use special coils or sequences to improve picture quality.
  • If your replacement is older than 30 years or you do not know what it is made of, contact your surgeon's office to confirm it is MRI-safe before scheduling.

What happens during an MRI with a knee replacement

When you arrive for your scan, the technologist will review your implant information and run it through their MRI safety software. Most facilities have a database of thousands of implant models with known safety profiles. If your replacement is in the database and marked safe, you will proceed to the scanning room.

You will lie on the MRI table with your knee positioned in a special coil — a wire cage that improves image quality. The machine will make loud knocking and buzzing sounds as it creates magnetic pulses. The scan typically takes 30 to 45 minutes depending on what the radiologist needs to see. You must stay still during each sequence, which usually lasts 3 to 10 minutes at a time.

The metal in your replacement will cause some image distortion around the implant itself, but this is expected and does not affect safety. Radiologists are trained to read MRIs of people with replacements and can usually see the structures they need — ligaments, cartilage, fluid in the joint — even with the artifacts present. If the image quality is too poor to answer the clinical question, your doctor may order a different type of imaging, such as ultrasound or a CT scan.

Implant cards and surgical records you need

After knee replacement surgery, you should receive an implant card or a packet of paperwork listing the manufacturer, model number, and materials of your replacement. This card is critical for any future imaging or medical procedures. Keep it in a safe place — your wallet, a drawer near your medical records, or a photo on your phone.

If you have lost your card, contact your surgeon's office or the hospital where you had surgery. They can print a replacement or provide the information in writing. If you do not know who performed your surgery or where, check with your primary care doctor or search your insurance records for the surgery date and facility name.

Some replacements are made of materials that are MRI-conditional, meaning they are safe only under specific conditions — for example, only at certain magnetic field strengths or only if no other metal is present nearby. Your paperwork will note this. The imaging center must follow these conditions exactly, so accuracy matters.

Older knee replacements and safety concerns

Knee replacements made before 1990 may contain ferromagnetic materials — metals that respond strongly to magnetic fields. These are rare in modern practice, but if your replacement is very old, your surgeon needs to confirm its safety before you schedule an MRI. Do not assume an old replacement is unsafe, but do not assume it is safe either.

Contact your surgeon's office with the year of your surgery and ask them to verify the implant model. If they cannot find the records, they may recommend a different imaging method or refer you to the hospital where the surgery took place. This step takes a few days but prevents complications.

What to tell the imaging center when you call

When you schedule your MRI, tell the scheduler that you have a knee replacement. They will ask which knee and may ask for the surgeon's name or facility. Have this information ready. Some centers will ask you to bring your implant card to the appointment; others will ask you to mail a copy or email a photo of it ahead of time.

If the center says they cannot scan you because of your replacement, ask them to check their database again or ask for the name of a facility that can. Most imaging centers scan people with knee replacements routinely, so a blanket refusal is unusual and may mean the scheduler is being overly cautious rather than following actual safety guidelines.

If you are scheduling an MRI for a body part far from your knee — such as your brain or shoulder — mention the knee replacement anyway. The technologist needs to know about all metal in your body before you enter the machine, even if it is not the area being scanned.

Alternatives if MRI is not possible

In the rare case that your replacement cannot be scanned safely, your doctor has other options. Ultrasound uses sound waves instead of magnets and works well for looking at ligaments, tendons, and fluid around the knee. CT scans use X-rays and are safe with any knee replacement, though they deliver more radiation than an X-ray. X-rays show bone clearly but not soft tissue.

Your doctor will choose based on what they need to see. If you have torn cartilage or a ligament injury, ultrasound or MRI is usually best. If you have a fracture or bone problem, X-ray or CT is better. Talk with your doctor about which imaging method will answer their question most clearly.

Frequently Asked Questions

Will the MRI machine pull my knee replacement out of my leg?

No. Modern knee replacements are securely fixed to your bone with cement or by growing into the bone surface. The magnetic field is not strong enough to pull out a properly healed replacement. The implant may feel warm during the scan, but this is normal and not dangerous.

Can I have an MRI right after knee replacement surgery?

Wait at least six weeks after surgery before scheduling an MRI. Your replacement needs time to heal and integrate with your bone. If imaging is urgent during this window, discuss other options with your surgeon — ultrasound or CT may be safer in the when ready post-surgery period.

What if I cannot find my implant card?

Call your surgeon's office or the hospital where you had surgery and ask for a replacement card or a written list of your implant details. Have the date of your surgery ready. This usually takes a few business days. Do not schedule your MRI until you have this information.

Does the MRI damage my knee replacement?

No. The magnetic field does not damage the metal or the materials bonded to your bone. MRI is a safe imaging method for people with knee replacements when the implant is confirmed to be MRI-safe beforehand.

Can I have an MRI if I have screws or plates in other parts of my body?

Most modern orthopedic hardware — screws, plates, rods — is MRI-safe. Tell the imaging center about all metal implants, not just your knee replacement. The technologist will check each one in their safety database before your scan.