A swan neck deformity describes a finger with a hyperextended PIP joint and a flexed DIP joint. The most common cause for a swan neck-like deformity is a disruption of the end of the extensor tendon. Conditions that loosen the PIP joint and allow it to hyperextend, for example conditions that weaken the volar plate, can produce a swan neck deformity of the finger. One example is rheumatoid arthritis. Another cause are conditions that tighten up the small (intrinsic) muscles of the hand and fingers, for example hand trauma or nerve disorders, such as cerebral palsy, Parkinson's disease, or stroke. The phenotype is HP_0006150 (Swan neck-like deformities of the fingers).