RA is an abbreviation of 'rheumatoid arthritis'.
Rheumatoid-arthritis or Osteo-arthritis?
Although rheumatoid arthritis can affect the knee, the common kind of arthritis of the knee is in fact osteoarthritis, which is generally less aggressive, affects fewer joints and tends to have fewer effects on the rest of the body.
Synonyms:
Rheumatoid arthritis
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