Yes, I agree... across the front of the ankle is a good spot.

I also use 1/2 patch behind the knee, just below the bend.
This however may numb the foot... so be careful with it, placed around the knee area.

I often use 1/2 patch on the top of the foot too, at times.
Lots of nerves there. If the foot is swollen, or discolored, I'd put the patches higher up. Pulling them off can do damage.

I had a patient who pulled off her Lidoderm too hastily and it bruised her whole upper arm.

I do not have RSD so I have not experienced that myself.

Feet and ankles must be problematical at times to stick Lidocaine patches on due to topography. I know Littlepaw mentions cream, but do you all know you can get liquid Lidocaine for external use? When having radiotherapy I suffered 2nd degree burns on and between my legs and this was an easy method of maximum application to a very lumpy area.
For me, in that condition, it dulled the pain for a few hours.

Dave.