Image credit: Phoenix119, 2014
It is caused by abnormal stress on the volar plate, the ligament around the middle joint of the finger (PIP joint).
The resulting shape looks similar to a swan’s neck, which is how the condition got its name.
Contents of this article:
What is a swan neck deformity?
For a swan neck deformity to occur, abnormal stress must be put on the ligament around the PIP joint of the finger.
The stress causes the ligament to loosen, which then causes hyperextension of the PIP joint. As a result, the PIP joint bows in towards the palm.