Pulsed Electro Magnetic Field Therapy.
Long story short - long history of using magnetic fields to influence body/physiological changes. Some evidence, but modern research shows human body reacts to quick changing, pulsed magnetic fields. They work in terms of inducing electrovoltaic potential changes at the cellular level & have been shown to a) reduce inflammation significantly b ) help with acute injuries c) reduce nerve induced pain symptoms.
Multiple mats/devices available (google for pawluk PEMF) - ranging from high power (and very expensive) to mats/full body equipment (low/high power, expensive). I'd go with a full body mat & try it at some chiro. Note, the mats are mostly made in Europe and are of Russian (QRS), German (BEMER) and Swiss (iMRS) origin. QRS is the simplest & has the most evidence. BEMER also has some studies behind it & is more expensive. iMRS claims to be the most modern etc and is equally expensive as BEMER.
I have tried iMRS and found it useful for general well being and some pain reduction. Again, try it for an extended period of time to see if it really works (to reduce impact of placebo effect) and see if its worth the effort.
Local devices include Somapulse (a variant of which I use & have found useful for localized pain).
In short, useful "adjunct therapy" if not the cure itself.

Another useful device which worked instantly for pain relief similar to TENS but much stronger and localized was InterX (this might be worth a shot, http://www.interxtherapycenter.com/) However, the device itself is very expensive (retail wise) and over time bodies do adapt to TENS. So it has to be continued, discontinued etc.