With a knee replacement, you need to prepare to go through security. After all, your knee can set off the medical detectors. If you're planning on flying, ask your doctor to provide you with a letter that talks about your surgery. It's also possible for airport security to ask to see your surgery scar.

In 2026, you generally do not need a doctor's note to fly with a knee replacement. Modern airport security screening, including the widespread use of Millimeter Wave scanners (Advanced Imaging Technology), is designed to handle internal medical implants. When you approach the security checkpoint, it is helpful to inform the TSA officer or security agent that you have a metal implant. While the implant may trigger a standard metal detector, the full-body scanner will simply highlight the area for the agent. If the alarm sounds, you may be subjected to a brief, professional pat-down of the joint area or a swipe with a handheld wand. Carrying a "medical device ID card" provided by your surgeon is a common practice for peace of mind, but security personnel are trained to recognize that these cards can be easily forged, so they rely on their own screening protocols rather than the documentation.