TRPC5 and rheumatoid arthritis: Hyperalgesia encompassing primary hyperalgesia of the affected joint and secondary hyperalgesia of distal, unaffected sites are a common symptom in RA and in rodent models of arthritis.4, 15 We measured primary hyperalgesia of the hindknee joint, and secondary hyperalgesia in the hindpaw of WT and TRPC5 KO mice following CFA-induced arthritis.