Are you certain you have PN , is that what is causing the wrist & hands symptoms?
What is the knee issue?
I'm thinking if you have a acute injury to knee or wrist/hands the pain blocking of the P stim might cause you to overdo as you mention.
If so it could be used to be more pain free during daily activities, but not to go back to doing more activities that may re-injure you.

Maybe this device is just not a fit for you.

Have you tried Low level laser for the knee, many chiropractors often have them to try a few test sessions. They can adjust the knee/hip/foot if that might be related to the knee pain, hand/wrist could be adjusted too. My chiro adjusted my foot, elbows, shoulders, wrist, he was very good, gentle and no crazy/scary maneuvers. He used LLLT, IF stim, and did soft tissue work too.

Just asking as the hand/wrist could be some sort of RSI or possibly even thoracic outlet syndrome (TOS). We have had quite a few members on our TOS forum that lifted weights this last year or 2.

You might list all symptoms/pain etc so we can help more.