Don't know Ed, but the initial PNS papers involved testing the effect of simulation to pinprick, showing a clear benefit in nociceptive pain.
In eight patients with intense chronic cutaneous pain, sensory nerves or roots. supplying the painful area were stimulated. Square-wave 0.1-millisecond pulses at 100 cycles per second were applied, and the voltage was raised until the patient reported tingling in the area. During this...
pubmed.ncbi.nlm.nih.gov
This one did chronic pain folks as well as the authors who had no known pain issues.
SPR at least is FDA approved for acute pain, suggesting they think it's capable of working on nociceptive pain.
And more over, a subset of arthritic joint pain is likely neuropathic.
Osteoarthritis pain: nociceptive or neuropathic? - PubMed
The preclinical models of OA in rodents respond really well to things like gabapentin for example, but gabapentin works great for a lot of animal pains.
With that said, I offer ablation first to knees and hips, discuss PNS vs RFA for shoulders.