DDx

Question 1

UQ joints affected by RA vs OA

Answer 1

RA: TMJ, entire CS, GHJ, elbow, CMC, PIP (spares DIP)
OA: lower CS, ACJ, 1st CMC, PIP, DIP

Question 2

LQ joints affected by RA vs OA

Answer 2

RA only: tarsals
OA only: LS, 1st MTP
both: hip, knee