Chances are, your knee implant will almost always set off the airport metal detector. That can trigger a hand pat-down screening by a Transportation Security Administration (TSA) agent. If the security checkpoint has a full-body scanner, you can go through that instead. You may still be searched a second time if the agents think they see something suspicious on the screen. You can print and carry a small TSA notification card to let the agent know you have an artificial knee. You also can speed things up by wearing clothes that easily let you reveal your surgical scar.