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- Stage I:
    - represents synovitis:
    - synovial membrane becomes hyperemic and edematous with foci of infiltrating small lymphocytes;
    - joint effussions w/ high cell count (5,000 to 60,000 per mm3)
    - x-rays will as yet show no destructive changes, but soft tissue swelling or osteoporosis may be seen;

- Stage II:
    - inflammed synovial tissue now proliferates & begins to grow into joint cavity across articular cartilage, which it gradually destroys;
    -narrowing of joint due to loss of articular cartilage;

- Stage III:
    - pannus of synovium;
    - eroded articular cartilage & exposed sub-chondral bone;
    - x-rays will show extensive cartilage loss, erosions around the margins of joint, and deformities may have become apparent;

- Stage IV:
    - end stage disease;
    - inflammatory process is subsiding;
    - fibrous or bony ankylosing of joint will end its functional life;
    - subcutaneous nodules associated w/ severe disease