All of the following joints are involved in rheumatoid ahritis, EXCEPT :

Joint involvement is the characteristic feature of rheumatoid ahritis (RA). In general, the small joints of the hands and feet are affected in a relatively symmetric distribution. The most commonly affected joints, in order of decreasing frequency, include the metacarpophalangeal (MCP), wrist, proximal interphalangeal (PIP), knee, metatarsophalangeal (MTP), shoulder, ankle, cervical spine, hip, elbow, and temporomandibular joints. Cervical spine involvement usually affects C1-C2.