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

Most modern knee replacements are MRI-safe, meaning the magnetic field used in an MRI scan will not damage the implant or cause it to move. However, the imaging center must know you have a replacement before you arrive. They will ask what type of implant you have, when it was placed, and may request documentation from your surgeon. Some older implants or certain components within a replacement are not MRI-safe, so the center needs to verify yours before scheduling.

The key difference between a safe scan and a problem is transparency. If you mention your knee replacement when you call to schedule, the process moves forward smoothly. If you do not mention it and arrive for your appointment, the center may refuse to scan you or delay your appointment while they track down your surgeon's records.

Key Takeaways

  • Most knee replacements placed in the last 15 years are MRI-safe, but the imaging center must verify your specific implant before your scan.
  • You will need to provide the name of your surgeon or the hospital where your replacement was done so the center can confirm the implant type.
  • Tell the imaging center about your knee replacement when you schedule, not when you arrive, to avoid delays or cancellation.
  • If your implant is not MRI-safe, your doctor can order a different imaging test such as CT or ultrasound instead.

What the imaging center needs to know about your implant

When you call to schedule an MRI, have ready the name and location of the hospital or surgery center where your replacement was performed. The imaging center will contact your surgeon's office to request your implant information. They need the manufacturer name and the specific model of the implant—for example, "Stryker Triathlon" or "Zimmer NexGen." This detail matters because some manufacturers make both MRI-safe and non-MRI-safe versions of the same product line.

If you have your surgical paperwork at home, look for the implant card or the operative report. Many surgeons give patients a card the size of a credit card that lists the implant details. If you cannot find it, the imaging center can retrieve the information from your surgeon's records, but this takes a few extra days. Starting the process early—at least a week before your scheduled scan—gives the center time to verify without rushing.

Why some knee replacements cannot have an MRI

Older knee replacements, particularly those placed before 2005, sometimes contain components that react to the strong magnetic field used in MRI machines. The magnet can cause heating in metal parts or, in rare cases, cause the implant to shift slightly. Certain cement types and some older metal alloys are more prone to these problems than newer designs.

Additionally, if your replacement includes a pacemaker, insulin pump, or other electronic device, you cannot have an MRI regardless of the implant itself. The magnetic field interferes with these devices. Your doctor will know whether you have such a device and will order a different type of imaging if needed.

What happens during an MRI with a knee replacement

The scan itself is the same as for anyone else. You will lie on a table that slides into a tube-shaped machine. The machine makes loud knocking and buzzing sounds for 20 to 45 minutes while it takes images. The technician can hear you through a speaker and will check on you periodically.

Because you have a knee replacement, the technician may ask you to keep your leg still or position it in a specific way. This helps produce clearer images and prevents any movement that could affect the scan quality. You will be given a call button to press if you feel uncomfortable or need to stop.

Alternative imaging if your implant is not MRI-safe

If your knee replacement is not MRI-safe, your doctor can order a CT scan (computed tomography) instead. A CT scan uses X-rays rather than magnetic fields and works with any implant. It takes less time than an MRI—usually 5 to 10 minutes—and produces detailed cross-sectional images of your knee.

Ultrasound is another option for some situations. It uses sound waves to create images and has no restrictions with any implant. Ultrasound is best for looking at soft tissues like tendons and ligaments around the knee rather than the implant itself.

Your doctor will decide which imaging method is best for what they are trying to diagnose. If they ordered an MRI specifically, ask them whether a CT or ultrasound would show what they need to see.

How to prepare for your MRI appointment

Wear loose, metal-free clothing. Remove all jewelry, watches, and metal objects before entering the imaging room. If you have any other implants—a hip replacement, spinal rods, metal plates from an old fracture—tell the imaging center about those too. Even small metal fragments from old injuries can cause problems in an MRI.

Arrive 10 to 15 minutes early so the staff can review your medical history and confirm your implant information one more time. Bring your insurance card and photo ID. If you have anxiety in enclosed spaces, tell the technician before the scan starts; they can keep the door open slightly or let you practice lying in the machine before the actual scan begins.

What to do if you do not have implant information

If you cannot locate your surgical paperwork and do not remember the name of your surgeon, start by calling the hospital where your surgery was performed. Give them your name and the approximate year of your surgery. Hospital records departments can usually find your operative report within a few business days.

If you had the surgery at an outpatient surgery center rather than a hospital, call that center directly. If the center has closed, the hospital that referred you there may have copies of your records. Your primary care doctor's office may also have a copy of your surgical summary.

Frequently Asked Questions

Will the MRI damage my knee replacement?

No, if your implant is MRI-safe. The imaging center verifies this before your scan. The magnetic field does not damage modern implants or cause them to move. The only risk is if an unsafe implant was scanned without verification, which is why disclosure is critical.

Can I get an MRI right after knee replacement surgery?

Most surgeons recommend waiting at least six weeks after surgery before any MRI. Your knee needs time to heal, and swelling must go down. Your surgeon will tell you when it is safe. If imaging is needed urgently, a CT scan or X-ray can be done sooner.

Do I need to remove my knee replacement before an MRI?

No. Knee replacements are surgically attached to your bone and cannot be removed without another surgery. The imaging center will scan you with the implant in place.

What if the imaging center says my implant is not MRI-safe?

Ask your surgeon's office to confirm. Sometimes imaging centers are overly cautious with older implants. If your surgeon confirms it is not safe, your doctor will order a CT scan or ultrasound instead. Do not insist on an MRI if the center has documented that your specific implant is unsafe.

How much does an MRI cost with a knee replacement?

Cost varies by location, your insurance plan, and whether the scan is done at a hospital or imaging center. Typical out-of-pocket costs range widely depending on your deductible and coverage. Call your insurance company and the imaging center to get a cost estimate before your appointment.