An old mate of mine put me onto the TENS machine a few years ago, he swore by it, so I got one for my back thats been crook for 30 odd years. It may have helped a bit, but not much. I only used it 3-4 times and gave up. I was then put onto a kinisiologist who gets the back feeling great.
The missus has used the TENS on her ankle, maybe a bit of relief but not the magic weapon we hoped. It probably does work on other issues but it didnt for us this time.
Cheers
JGM