This info can be found on TSA website. (I found it today, so I assume it is the most up-to-date.)


Persons with Prosthetic Devices, Casts, Body Braces

Screeners will need to see and touch your prosthetic device, cast or support brace as part of the screening process.
Screeners will not ask nor require you to remove your prosthetic device(s), cast, or support brace.
During the screening process, please do not remove or offer to remove your prosthetic device(s).
You have the option of requesting a private screening at any time during the screening of your prosthetic device, cast or support brace.
You have the right to refuse the offer of a private screening; however, you will need to allow the screening to be conducted publicly if you wish to proceed beyond the security checkpoint.
You may have a companion, assistant or family member accompany and assist you into the private screening area (once he or she has been screened) and remain throughout the screening process.
TSA will make every effort to have two screeners of the same gender as the passenger being screened present during the private screening.
If you are too weak or unstable on your feet to stand for an HHMD search because of your prosthetic device, cast, or support brace, you may request to sit down after you have passed the WTMD.
Please notify screeners if you need assistance during the screening process such as a hand, arm, or shoulder to lean upon, or a chair in which to sit. At any time during the screening process you can request a disposable paper drape for privacy.
Screeners will need to perform explosive trace detection (ETD) screening of your prosthetic device, cast, or support brace.
The screener will describe the ETD sampling procedure in advance to help you along with the process.
During the screening process, the screener will take a swab sample from the exterior of your prosthetic device, cast, support brace, palms, fingers, and footwear.
The ETD screening process may require you to lift or raise some of your clothing in order to obtain the ETD sample. (Sampling areas can be accessed by you lifting your pant leg or shirtsleeve or by raising your skirt to knee-level.)
The screener should offer you a private screening if clothing will need to be lifted or raised in order to obtain the ETD sample. You will not be required to remove any clothing during the process or remove or display the belt that holds your prosthetic device to your body.
If the device alarms the ETD and the screener cannot resolve the alarm, you will not be permitted into the sterile area.