Welcome to Connect, @k135, @cindy78 and @sassycat. While we wait for others to join in and share their insights, I’d like to offer this information for Mayo Clinic, about CRPS.
Complex regional pain syndrome (CRPS) appears to be an autoimmune condition, in which the body responds in an unusual way to a perceived threat. As the immune system fights to defend the body, inflammation occurs. https://www.mayoclinic.org/diseases-conditions/crps-complex-regional-pain-syndrome/symptoms-causes/syc-20371151

I’m certain fellow members, @mlross4508 @gracie2018 @suerc @healingone @scruffy1 @barbbie @jeffyoung @dmac5 and others will return to share their insights with you. You might also be interested in viewing these Connect discussions:
– CRPS and Nevro SCS https://connect.mayoclinic.org/discussion/crps-and-nevro-scs/
– Anyone used Spinal Cord Stimulation for pudendal nerve entrapment? https://connect.mayoclinic.org/discussion/anyone-experienced-in-using-scs-for-chronic-painb/

I thought I’d provide more details about the treatment that @k135 has mentioned–Neridronate: https://journals.sagepub.com/doi/full/10.1177/1179559X17732971

Neridronate is approved in Italy for CRPS but the FDA has not approved this drug or its equivalents in the USA. Although patients with CRPS Type 1 have found success and gone into remission, there is no research that shows anything from a new injury, serious illness/disease, extreme stress, or simply stubbing your toe wouldn’t cause a return of the CRPS either in the same place or possibly in a new area.
"Major trial of CRPS ‘potential cure’ drug Neridronate halted” https://www.grunenthal.com/en/press-room/view-media-statement?pressReleaseId=01a51358-e3c6-493f-9353-377a34884dd7