Do knee replacements cause metal detectors to go off? A guide for travelers

September 30, 2025 •

4 min read

According to the American Academy of Orthopaedic Surgeons, over 90% of total knee replacement recipients will set off airport metal detectors. This is a common concern for travelers and patients, leading many to ask, "Do knee replacements cause metal detectors to go off?" The short answer is yes, and understanding the reasons why, along with preparing for airport security, can make your travel less stressful.

Quick Summary

Modern knee replacements, which contain metallic alloys, will very likely trigger metal detectors. This is not a cause for alarm, but travelers should anticipate additional screening procedures, such as a full-body scan or a wanding. Preparing for security with an implant involves informing TSA officers and allowing extra time for screening.

Key Points

Expect an Alarm: The vast majority of knee implants contain metal alloys that will trigger walk-through metal detectors.
Communicate with Security: Inform the security officer about your knee replacement and its location before going through the detector to ensure a smooth process.
Screening Options are Available: You will likely be directed to an Advanced Imaging Technology (AIT) body scanner, or you can opt for a handheld wand and a pat-down.
Medical Cards are Optional: A medical implant card is no longer required or guaranteed to speed up the process, as you will still be screened. The TSA Notification Card is for discreet communication only.
Safety is Not a Concern: The materials used in knee replacements are biocompatible and safe, and the screening equipment will not harm your implant or your body.
Plan for Extra Time: Account for a few extra minutes during security checks to allow for the secondary screening process.

Understanding Why Knee Replacements Trigger Metal Detectors

Total knee arthroplasty (TKA) involves implanting a prosthetic joint to replace a damaged knee. The prosthetic is made of durable, biocompatible materials, which typically include metal alloys. The presence of these metal components is what causes metal detectors to sound an alarm. Security screening equipment, including both walk-through arches and handheld wands, operates by detecting changes in an electromagnetic field caused by metallic objects. Even with advances in technology that have improved the wear-resistance and design of implants, the fundamental metal components mean detection is highly probable.

The Materials Used in Knee Implants

While the alarms may be sensitive, the materials used in modern implants are safe and biocompatible. They are not magnetic and will not be affected by the metal detectors themselves. Common materials include:

Cobalt-Chromium Alloys: A hard-wearing and durable material that is frequently used for the femoral (thigh bone) component of the implant. Due to its composition, it is easily detected by security screening equipment.
Titanium Alloys: Lighter and more flexible than cobalt-chromium, titanium is often used for the tibial (shin bone) baseplate. While still metal, titanium-based implants may have a slightly lower detection rate compared to cobalt-chromium, though they can still trigger alarms.
Polyethylene: This is a high-density plastic used as the spacer or bearing surface between the metal components, providing a smooth gliding surface. This material does not set off metal detectors.

Factors Influencing Detection

Several factors can influence the likelihood of a knee implant triggering a metal detector:

Type and Size of the Implant: Larger, total joint replacements are almost guaranteed to set off an alarm, while smaller plates, screws, or wires are less likely to be detected by walk-through machines, though they are often found with a handheld wand.
Sensitivity of the Detector: Security detectors have adjustable sensitivity settings. In high-security areas, or during periods of increased security threats, sensitivity may be higher, increasing the chance of an alarm.
Location and Shielding: Implants located deeper within the body, such as hip replacements, may be detected less frequently than the more superficial knee replacements. The amount of soft tissue, bone, and cement around the implant can affect the signal.

Navigating Airport Security with a Knee Replacement

Traveling with a knee replacement can be a smooth process with some preparation. It's best to be proactive and communicate clearly with security staff. Following these steps can help reduce stress and delays.

Preparing for the Security Checkpoint

Before your trip, it's wise to plan ahead. Arrive with plenty of time to account for the possibility of a secondary screening. The Transportation Security Administration (TSA) is familiar with orthopedic implants and has established procedures to handle the situation calmly and efficiently.

Communicating with Security Officers

Upon reaching the checkpoint, inform the TSA officer that you have a knee replacement and indicate the location of the implant. This transparent communication helps the process go smoothly. While a doctor's note or special ID card used to be common, it is no longer required and will not exempt you from screening. The TSA offers a printable Notification Card that you can discreetly present to the officer if you prefer.

Screening Options with an Implant

When the metal detector alarm sounds, you will be directed to alternative screening. You have two primary options:

Advanced Imaging Technology (AIT) Scan: The full-body scanner uses millimeter wave technology to screen for metallic and non-metallic objects. Many patients prefer this method as it's quick and reduces the likelihood of a pat-down. Your implant will be visible on the scan, which is why you alerted the officer beforehand. The scans are safe and do not use harmful radiation.
Handheld Wand and Pat-Down: If you decline the AIT scan, you will receive a pat-down and a handheld wand screening. The wand is typically more sensitive than the arch detector and will pinpoint the exact location of the implant. You can request a private screening area if you prefer.

A Comparison of Screening Procedures for Travelers with Knee Replacements


Screening Method	Experience with Implant	Time Expectation	Privacy Level	Additional Screening	Notes
Walk-Through Metal Detector	Almost certain to alarm due to metallic components.	Brief, but requires secondary screening.	Low	Handheld wand or AIT scan.	The initial point of contact for screening; the alarm is the trigger for further action.
Advanced Imaging Technology (AIT)	The image will show the implant, validating your prior notification.	Usually faster than a pat-down.	High (image is not stored).	May still involve a targeted pat-down of the implant area.	Considered a less invasive option for many travelers.
Handheld Wand	Will detect the metal and cause the wand to alarm directly over the implant site.	Depends on the thoroughness of the screening.	Medium (can request private screening).	Part of a pat-down, not a standalone option.	Officer can confirm the location of the implant without extensive pat-down.
Pat-Down	Officer will feel the area around the implant during the process.	Potentially the most time-consuming.	Medium (can request private screening).	The primary method for those declining AIT or for other reasons.	Provides an alternative for travelers with specific medical devices or preferences.

Conclusion

In summary, if you have a knee replacement, it's highly likely that you will set off metal detectors during security screening, especially at airports. The metals used in these durable implants, such as cobalt-chromium and titanium, are readily detected by modern security technology. Rather than worrying, the key is to be prepared and communicative. By informing security officers of your implant and understanding the screening options available, you can navigate security with ease and minimize any potential delays. While a joint replacement ID card is optional, transparent communication is the most effective tool for a smooth and stress-free travel experience. So, don't let the thought of an alarm deter you—plan ahead and enjoy your journey.

For more information on travel tips for individuals with orthopedic implants, you can visit the Transportation Security Administration's website.

Frequently Asked Questions

Most modern knee replacements use metallic alloys and will trigger metal detectors. While some smaller components or specific materials may be less likely to be detected, it is safest to assume your implant will set off the alarm and prepare for secondary screening.

Yes, similar to knee replacements, hip replacements are also made with metallic components and are very likely to trigger metal detectors. The process for navigating airport security is the same for both types of implants.

Yes, it is completely safe. The walk-through metal detectors use harmless electromagnetic fields, and the Advanced Imaging Technology (AIT) scanners use non-ionizing millimeter waves. Neither will damage your implant or cause you any harm.

No, a doctor's note or medical ID card is not required by the TSA and will not exempt you from screening. Security officers are trained to handle screenings for individuals with implants. You can, however, use the TSA Notification Card for discreet communication.

The best approach is to be prepared. When you get to the security checkpoint, inform the officer that you have a knee replacement and tell them its location. They will then direct you to the appropriate secondary screening, such as the full-body scanner or a wanding.

Yes, the Advanced Imaging Technology (AIT) scanner is designed to detect both metallic and non-metallic objects, so the image will show the prosthetic joint. This is a normal part of the security process.

It is wise to plan for some extra time. While the process is streamlined, the need for secondary screening means you will not simply walk through the metal detector. However, clear communication and following instructions will minimize any delays.