Sorry to hear of the tendonitis mate, hope you keep it under control.
I had a very annoying thing happen at a gig a few weeks ago. Halfway through the second set, playing a fairly busy line, and the middle finger on my left (fretting) hand just curled over into a claw shape and locked there
Panic stations...I had to switch into root-notes mode for the rest of the song, and give my hand a good shaking out aftewards. I realised I had left my watch on (usually take it off to play), and that my recently lowered strap was forcing my wrist into a 90 degree angle. Not good, so back to Funk Position and no problems since.
It was a wake up call to be honest, sod looking "rawk", I want to be playing for as long as I can
Cheers,
Si