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Overview
Deformity of a finger resulting in finger being contracted in a position of hyperextension at the PIP joint and flexion at the DIP joint
In some instances there can also be flexion at the MCP joint
Common Causes
Laceration at the extensor mechanism
Finger jam on the distal phalanx of an extended finger
Chronic inflammation such as from rheumatoid arthritis
All causes result in dysfunction of the extensor mechanism in the finger
What Happens at the Extensor Mechanism
Results from imbalance in the extensor mechanism of the affected finger
Is caused due to either:
Dysfunction of the extensor mechanism at the distal phalanx (extensor mechanism is too lax) - not enough pull causes flexion at DIP joint
When the extensor mechanism at the DIP joint is compromised, the remaining extensor force is redirected to the PIP joint, leading to PIP hyperextension
The pull from the FDP tendon at the DIP joint causes flexion at the DIP joint
Dysfunction of the extensor mechanism at the proximal phalanx (extensor mechanism is too tight) - too much pull causes hyperextension at PIP joint
The hyperextension throws off the balance of forces in the extensor mechanism, resulting in a weakening of the extensor pull at the DIP joint
With reduced extensor force, the FDP tendon can then pull the DIP joint into flexion
Kaushik K S. (Photographer). (2024). Swan Neck Deformity. Retrieved from https://www.physio-pedia.com/Swan-Neck_Deformity
Treatment
Orthoses:
Extension block orthoses can be fabricated to block the PIP joint from going into hyperextension, while allowing PIP flexion to occur
Rebalances the forces in the finger
Depending on serverity of deformity, can be worn at all times of the day or just during the day
Serial extension orthoses can be fabricated to apply a gentle and sustained extension force/stretch to the DIP joint to gradually remodel the stiff tissue
Usually worn at all times of the day and re-fabricated once a week to ensure there is still a gentle stretch
Severe or chronic deformities are likely not going to resolve without surgical intervention
AROM:
Joint blocking to focus on DIP joint extension to counteract the flexion deformity
Joint blocking to focus on PIP joint flexion to counteract the extension deformity
Tendon glides to prevent overall stiffness
PROM:
Stretch DIP joint into extension to counteract the flexion deformity
Stretch PIP joint into flexion to counteract the extension deformity
Stretch MCP joint into extension to counteract the flexion deformity (if present)
Surgery:
Early-stage: Goal is to stop the PIP joint from hyperextending by tightening tendons on the volar surface of the joint to improve stability
Late-stage: Joint fusion or joint replacement may be needed
Quiz Questions
What joint positions characterize a swan neck deformity?
A. Hyperextension at the PIP and flexion at the DIP
B. Flexion at the PIP and DIP joints
C. Hyperextension at the DIP and flexion at the PIP
D. Hyperextension at all finger joints
Which of the following is a common cause of swan neck deformity?
A. Rheumatoid arthritis
B. Carpal tunnel syndrome
C. De Quervain’s tenosynovitis
D. Lateral epicondylitis
What does dysfunction of the distal extensor mechanism cause?
A. Extension of the DIP joint
B. Flexion of the DIP joint due to loss of extension force
C. Hyperextension of the DIP joint
D. Dislocation of the DIP joint
In a swan neck deformity, the force from the FDP tendon contributes to:
A. PIP joint flexion
B. MCP joint hyperextension
C. DIP joint flexion
D. Extension of all finger joints
What is the purpose of an extension block orthosis in swan neck deformity treatment?
A. To restrict all joint motion
B. To flex the DIP joint
C. To immobilize the MCP joint
D. To prevent PIP hyperextension while allowing PIP flexion To restrict all joint motion
Quiz Answers
A
A
B
C
D
References
Lane, R., & Nallamothu, S. V. (2025). Swan-neck deformity. In StatPearls. StatPearls Publishing. http://www.ncbi.nlm.nih.gov/books/NBK525970/
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