A knee brace with an inflatable air bladder. In a post-surgical embodiment the brace includes a rigid shell that fits behind the knee. The rigid shell includes an inflatable air bladder on its posterior surface. A wrap is placed around the knee and the air bladder. When the air bladder is inflated, the knee is urged in the posterior direction—thereby decreasing flexion. In a rehabilitative embodiment, a rigid shell is placed over the anterior portion of the knee. An air bladder is positioned between the rigid shell and the knee. The rigid shell is held in place using the securing straps of the rehabilitative brace. When the air bladder is inflated the knee is again urged in the posterior direction.