What causes a type II swan-neck deformity in rheumatoid arthritis (RA)?

Updated: Jun 11, 2021
  • Author: Michael Neumeister, MD, FRCSC, FACS; Chief Editor: Joseph A Molnar, MD, PhD, FACS  more...
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A type II deformity has an appearance similar to that of the type I deformity; however, PIP joint flexion is influenced by the position of the MP joints. When the MP joints are extended or radially deviated, passive PIP joint flexion is limited; when the MP joints are flexed or ulnarly deviated, a greater degree of PIP joint flexion is possible. As the patient's RA disease continues to progress, radial deviation of the metacarpals and volar subluxation of the MP joints increase secondary to increased tightness of the intrinsic muscles. Consequently, a swan-neck deformity develops.

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