A knee extension assist device that includes: a frame, a support structure, a base and an articulated knee brace. The frame has a first section pivotably connected to a second section by a pair of hinges. The support structure is slidably attached to the frame to provide pivotal movement of the two sections. The base includes a motor that moves the frame between extended and retracted positions. The articulated knee brace receives a patient' leg and has a pair of upper legs connected by a pair of hinges to a pair of lower legs. A pair of shafts connects the hinges in the brace to the hinges on the frame and a pair of connecting members connects the lower legs to the second section of the frame. The pivotal movement of the frame causes a force to be exerted on the soft tissues in the knee of the patient.