Does anyone else get stiff muscles/joints with their PN?

My husbands is really flaring these days and along with the usual pain/burning etc. he says his feet feel stiff like they won't bend, with muscle soreness up his calves.
His hands are extremely painful and stiff and the first two knuckles are slightly swollen.

Is it the PN, or is something else going on?

Any thoughts?

Thanks, Linda