Swan neck deformity is/are seen in :

Ans: A (Rheumatoid arthritis) Hand joint Affected in Rheumatoid Arthritis# Boutonniere deformity-1- Flexion contracture of the PIP joints & extension of the DIP joints# Z deformity - Radial deviation at the wrist with ulnar deviation of the digits, often with palmar subluxation of proximal phalanges# Swan neck deformity - Hyperextension of PIP joints with compensatory flexion of the DIP jointsHyperextension of first interphalangeal joint & flexion of the first meta carpophalangeal joint with a consequent loss of thumb mobility.Swan Neck Deformity It is a deformed position of the finger, in which the joint closest to the fingertip is permanently bent toward the palm while the nearest joint to the palm is bent away from it (DIP hyperflexion with PIP hyperextension).# It is commonly caused by injury or inflammatory conditions like rheumatoid arthritis or sometimes familial (congenital, like Ehlers-Danlos syndrome)Fig: Deformities in rheumatoid arthritisCauses of this deformity includerheum a toid arthritis (most common)mallet finger (due to rupture of lateral slips at their junction with bone) cerebral palsy (due to muscle imbalance)congenital joint laxityFig: Swan neck deformity