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 login to view 5 more bullets Pathoanatomy FDP tendons of long, ring, and little fingers share a common muscle belly login to view 2 more bullets 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 login to view 2 more bullets Operative release FDP of injured digit login to view 2 more bullets