Boutonniere deformity is a sign indicative of rheumatoid arthritis, although it also is a result of a blow to the finger. Its basic appearance is that the middle joint of the injured finger bends down, while the fingertip bends back. Formally, it manifests as hyperflexion at the proximal interphalangeal joint with hyperextension at the distal interphalangeal joint. The disorder is associated with tendon damage It is closely related to swan-neck deformity, which is more joint- than tendon-based
Treatment of deformities caused by trauma preferably is conservative and nonsurgical, although if surgery is required, it should not be delayed more than 3 weeks after the injury. If caused by rheumatoid arthritis, medical management of that disease is paramount, although supportive measures such as padding and splints may be indicated.