How is a swan-neck deformity in rheumatoid arthritis (RA) assessed?

Updated: Jun 11, 2021
  • Author: Michael Neumeister, MD, FRCSC, FACS; Chief Editor: Joseph A Molnar, MD, PhD, FACS  more...
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When evaluating the finger, the proliferation of synovium around a joint can be detected by observing fluctuant swelling beneath the examiner's fingers when the joint is held in 45° of flexion.

The active and passive ranges of motion of each joint should be measured with a goniometer. Hyperextension is recorded as a negative value. In addition, the lateral stability of each joint should be tested by applying 3-point pressure, with the finger in extension.

The finger in question should also be tested for intrinsic (interosseous and lumbrical) muscle tightness. The examiner should hold the MP joint in full, passive extension and flexion, and then gently flex the PIP joint with the other hand. In the normal finger, full PIP joint flexion is possible in extension and flexion of the MP joint. In contrast, in the presence of intrinsic tightness, resistance to PIP joint flexion is encountered when the MP joint is in extension (and the intrinsics are already passively stretched), although when the MP joint is in flexion, passive PIP flexion is possible. The angle of passive PIP flexion is determined with a goniometer and recorded.

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