I had a very bad experience with my aunt who has MS. This was 2005 or so, before the NOS, but they didn't want her to walk through the metal detector with any assistive device, so they asked if she could walk through the metal detector on her own. She is very independent and hates to be limited by her disability, so she said yes. She took a step forward and literally tumbled through the WTMD. The TSO on the other side just stood there looking at her, didn't bother to try and catch her or anything. Sigh.

So in my experience, yes, you can go through the WTMD in just about any way you want.

That being said, based on the way WTMDs work, hopping, bobbling, or pausing instead of walking through smoothly at a constant pace would tend to interfere with the accuracy of the WTMD, so it probably shouldn't be allowed. Security Theater at its finest.

This may be one case where electing to go through the NOS instead of WTMD is actually a superior option (similar to the people with hip implants). Go through the NOS, they will pat down the 'anomaly' where your brace is, and that should get you through with a minimum of fuss/contact/violation.

The danger of a single exposure to radiation is truly insignificant, especially when there are other health concerns with higher risks. It would be awful if you did further damage to your knee by removing your brace and hobbling around the checkpoint unsupported.