Summary Quadriga Effect is characterized by an active flexion lag in fingers adjacent to a digit with a previously injured or repaired flexor digitorum profundus tendon. Diagnosis is made clinically with the inability to fully flex the fingers of the hand adjacent to the injured finger. Treatment is observation if patient is minimally symptomatic but may involve release of FDP tendon of injured digit if symptoms impact patient's activity demands. Etiology Mechanism most commonly caused by a functional shortening of the FDP tendon due to over-advancement of the FDP during tendon repair >1 cm advancement associated with quadriga adhesions retraction of the tendon "over-the-top" FDP repair of the distal phalanx after amputation Pathoanatomy FDP tendons of long, ring, and little fingers share a common muscle belly therefore excursion of the combined tendons is equal to the shortest tendon improper shortening of a tendon during repair results in inability to fully flex adjacent fingers Anatomy Flexor digitorum profundus Zones of the flexor tendons most injuries resulting in quadrigia involve Zone I Presentation Symptoms inability to fully flex the fingers of the hand adjacent to the injured finger patient may complain of "weak grip" Physical exam upon making a fist the fingers adjacent to the injured digit will not reach full flexion grip strength decreased Imaging Radiographs usually not required Treatment Nonoperative observation indications mild symptoms not affecting quality of life Operative release FDP of injured digit indications severe symptoms limiting function