Doc said my muscles were knotted in my neck causing my pain there. He wanted me to go to physiotherapy. But I have a tens machine at home and use it . Thankfully it is easing up now. How this happened I have no clue.
In my experience any knotted muscles are best mid-term solved sustainably with physiotherapy. So possibly they will return regularly if you don't get the cause under control, which may be posture.
The TENS machine must I'm thinking have worked A) best case by the electrical currents helping the tissue self-heal by supporting natural body currents or B) (as is usually said) by fogging over the pain (Gate Theory).
A) Some people selling them say that micro currents (microcurrents units) are even better because at a more natural level than TENS currents, but it's a lot more expensive whether buying or appointments.
I listened to a talk on Murphree's drtalks fibro summit Saturday by Dr. Rob Vanbergen "Reduce Your Pain With Micro Currents".
That's how I came to think that maybe a TENS can heal more than is generally said.
If I could tolerate currents, I'd try both and also the electrical brain treatments (e.g. TMS) that are recently being trialled more and more.
B) Electrically fogging over the pain reminds me of the mainstream theory behind applying cortisone: that if you suppress inflammation, the body may get a chance to heal. Generally, I don't find suppression is the right way. But if we do, I think it's best to make sure we additionally support the body as we can. In this case if the TENS is stopping pain signals, then that can enable us to move more normally, get out of relieving postures, which can cause other problems (contributing to apparently moving fibro pain). For me I've found that suppression makes me continue with unhealthy things instead of identifying and preventing or alleviating triggers.