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  • Duck-bill deformity

  • Recurvatum deformity

  • Volar plate injury


  • 736.22 Swan-neck deformity


  • M20.03 Swan-neck deformity

  • M20.031 Swan-neck deformity of right finger(s)

  • M20.032 Swan-neck deformity of left finger(s)

  • M20.039 Swan-neck deformity of unspecified finger(s)


  • 4D: Impaired Joint Mobility, Motor Function, Muscle Performance, and Range of Motion Associated with Connective Tissue Dysfunction


Patient is a 32-year-old woman diagnosed with rheumatoid arthritis 3 years ago. She experienced an exacerbation of symptoms, with increased pain and inflammation in both hands 2 months ago, and was seen by her rheumatologist for medical management. Although pain and inflammation have subsided, she now reports difficulty in her job as a music teacher at the local high school. Her chief complaint is that she is unable to demonstrate playing instruments because her “fingers won’t cooperate.” When trying to straighten the fingers, “the middle joint bends backwards and gets in the way.”

When asked to extend her fingers, the patient moved the index, long, and ring fingers of her right hand into a position involving proximal interphalangeal (PIP) joint hyperextension and distal interphalangeal (DIP) joint flexion; the small finger moved normally into extension. After demonstrating this, the patient then had mild difficulty returning to a flexed position (unintended slight hesitation). The MP joints were slightly swollen, but appeared to be in good alignment and functioning properly. Wrist motion was within normal limits (WNL).



  • Injury or loosening of the volar plate (ligament connecting proximal and middle phalanx that prevents hyperextension of the PIP)

  • Hyperextension of the PIPjoint and flexion of the DIP joint

  • Duck-bill deformity is the same issue in the thumb less one joint

FIGURE 177-1

Boutonnière (A) and swan-neck (B) deformities. (From Toy EC, Patlan JT. Case Files: Internal Medicine. 3rd ed. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.)

Essentials of Diagnosis

  • RA most common cause of swan-neck deformity

  • Chronic inflammation loosens the volar plate and disrupts ligaments and other connective tissues making PIP susceptible to hyperextension

  • Migration of the lateral bands of the extensor hood dorsally, to become extensor forces at the PIP

    • This neutralizes the oblique retinacular ligaments’ ability to influence extension of the DIP, resulting in imbalance between the flexors and extensors which results in flexion of the DIP

  • As a result, extensor tendon tightens causing DIP to pull into flexed position

  • Swan-neck classification by Nalebuff4

    • I: PIP joint flexible in all positions

    • II: PIP motion limited only by tenodesis effect

    • III: Fixed PIP joint contracture, x-ray normal

    • IV: X-ray shows ...

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