[Deformities of the finger joints].

Extension of the fingers is a complex act. Boutonnière deformity is defined by flexion at the proximal inter-phalangeal (PIP) joint and hyperextension at the distal interphalangeal (DIP) joint due to disruption of the central slip of the extensor tendon. Swan neck deformity is defined by hyperextension at the PIP joint and flexion at the DIP joint, and the pathology is divided into intrinsic, extrinsic, and articular. The deformities are a result of imbalance of the tendons and ligaments in the fingers. Treatment is depending on the underlying cause and includes surgery and non-operative treatment. Functional gain and risk must be realistically assessed.