Merck Manual

Please confirm that you are a health care professional

honeypot link

Swan-Neck Deformity


David R. Steinberg

, MD, Perelman School of Medicine at the University of Pennsylvania

Last full review/revision May 2020| Content last modified May 2020
Click here for Patient Education
Topic Resources

A swan-neck deformity consists of hyperextension of the proximal interphalangeal (PIP) joint, flexion of the distal interphalangeal (DIP) joint, and sometimes flexion of the metacarpophalangeal (MCP) joint.

Boutonnière Deformity and swan-neck deformities

Boutonnière and swan-neck deformities

Although characteristic in rheumatoid arthritis Rheumatoid Arthritis (RA) Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease that primarily involves the joints. RA causes damage mediated by cytokines, chemokines, and metalloproteases. Characteristically... read more Rheumatoid Arthritis (RA) , swan-neck deformity has several causes, including untreated mallet finger Mallet Finger Mallet finger is a flexion deformity of the fingertip caused by avulsion of the extensor tendon, with or without fracture, from the proximal end of the distal phalanx. (See also Overview of... read more , laxity of the ligaments of the volar aspect of the proximal interphalangeal (PIP) joint (eg, as can occur after rheumatic fever or in systemic lupus erythematosus [SLE] as Jaccoud arthropathy), spasticity of intrinsic hand muscles, rupture of the flexor tendon of the PIP joint, and malunion of a fracture of the middle or proximal phalanx. The inability to correct or compensate for hyperextension of the PIP joint makes finger closure impossible and can cause severe disability.

Treatment of swan-neck deformity is aimed at correcting the underlying disorder when possible (eg, correcting the mallet finger or any bony malalignment, releasing spastic intrinsic muscles). Mild deformities in patients with rheumatoid arthritis may be treated with a functional ring splint.

True swan-neck deformity does not affect the thumb, which has only one interphalangeal joint. However, severe hyperextension of the interphalangeal joint of the thumb with flexion of the metacarpophalangeal (MCP) joint can occur; this is called a duck bill, Z (zigzag) type, or 90°-angle deformity. With simultaneous thumb instability, pinch is greatly impaired. This deformity can usually be corrected by interphalangeal arthrodesis along with tendon reconstruction at the MCP joint.

Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read
Test your knowledge
IgG4-Related Disease
Immunoglobulin G4-related disease (IgG4-RD) is a chronic immune-mediated fibroinflammatory disorder that often manifests with tumor-like and/or painless enlargement of multiple organs. When limited to the head and neck region, IgG4-RD accounts for about 25 to 50% of cases of which of the following?
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest