Sagittal band rupture is a cause of a bent finger. The sagittal band is part of the extensor mechanism in the finger.
It allows extension (straightening) at the knuckle of the finger (metacarpal phalangeal joint, MP joint) of the finger. The bend, or flexion, is located at the knuckle of the finger (see photo). Acute sagittal band injuries at the metacarpophalangeal joint may result in subluxation or dislocation of the extensor tendons and may cause pain and swelling at the MP joint and limit active extension of the MP joint (bent finger at the MP joint).
These injuries can be treated with nonoperative treatment (splinting), surgical repair or reconstruction. The treatment varies on the degree of deformity, the length of time it has been present, passive correctability of the extension and ability to hold the extension once it is passively corrected.
Closed Treatment of Nonrheumatoid Extensor Tendon Dislocations at the Metacarpophalangeal Joint. Louis W. Catalano III, MD, Salil Gupta, MD, Raymond Ragland III, MD, Steven Z. Glickel, MD, Caryl Johnson, BS, O. Alton Barron, MD J Hand Surg 2006;31A:242–245.