Swan-neck deformity is -
Important hand deformities of hand in RA

Boutonniere deformity: Flexion contracture of PIP joint and extension of the DIP joint.
Swan neck deformity: Hyperextension of PIP joint and flexion at DIP joint.
Z-deformity: Radial deviation of the wrist with ulnar deviation of fingers.
Hyperextension of 1st interphalangeal joint and flexion of MP joint.
Flexion of Metacarpophalangeal joint and extension at interphalangeal joint
Extension at Proximal interphalangeal joint and flexion at Distal interphalangeal joint
Flexion at proximal interphalangeal joint and extension at distal interphalangeal joint
Extension at Metacarpophalangeal joint and flexion at interphalangeal joint