My wife has a strange pain at the calf. Strong. (lower leg -10 cm down and behind the knee ) We do not know what it is, and how to treat with frequencies.

1. Try the Zapper or Hulda Clark Zapper Preset in Contact Mode or PEMF or the Laser.

You can also do both treatments at one time. Zapper and Laser or Laser and PEMF etc.

To do this set the Option "follow OUT 1" for the Channel 2 under the SETTINGS tab.

2.Lack of Magnesium COULD be the cause for some people. It was for me.
In the night I would wake with SEVERE cramp in calf muscle. SO, much I almost couldn't breathe.

If so, you need to find out the Why.
It could be too much Calcium. 
We usually get more than enough Calcium in out diet and supplementing with it is probably not necessary, and could Cause pain.

Is it like a Charlie Horse?

There is a Balance the body needs. Calcium contracts, Magnesium relaxes.
If it was me, I would try Magnesium Oil, topically or if available soak in a hot bath with Epsom salts added.

OR, an infection. 

Has the pain, "Wandered" from one joint to another?
THAT is a sign of an infection from a pathogen.

3.This can be also blood vessel problem. Your wife should also try with cold water from the feet slowly upward shower, allways from the feet in direction heart. Also called vena varicosa.

For more details, please check the link from:
https://www.spooky2.com/forums/viewtopic.php?f=12&t=7859