RA:
MTPJ medial aspect
Earliest 5th MTPJ - lateral aspect
Usually no involement of IPJ
Psoriasis:
IPJs most commonly involved, also MTPJ
Reiter's:
Similar to psoriasis
Upper limb almost never involved
Gout:
Lobulated masses
Overhanging edges, may be far away from the joint
No IPJ involvement
