Swan neck deformity is a clinical sign in degenerative diseases e.g., rheumatoid arthritis. It is found in approximately 50% of cases of rheumatoid arthritis. It is characterized by hyperextended proximal interphalangeal joint and flexed distal interphalangeal joint. The diagnosis is based on history and clinical examination. Initially, it is treated by splinting. Volar plate advancement with central slip tenotomy is reserved for progressive cases. Reference: https://www.orthobullets.com/hand/6013/swan-neck-deformity