What Causes Stiffness And Pain In Wrist Post Open Reduction Of Fracture?

broke my wrist on january 12 the distal radius. had closed reduction and 2 weeks later open reduction with screws and plate, My hand now is so stiff and really aches ,i cant write or do much with the hand ,not much range of motion and little strengh i am in physicl therapy but it does not help much what do i do?