Abstract: A knee brace for preventing abnormal anterior or posterior movement, and abnormal internal or external rotations, of the tibia relative to the femur includes a femoral cuff adapted for attachment to the thigh, a tibial cuff adapted for attachment to the calf and a pair of linkage assemblies interconnecting the cuffs. Each linkage assembly comprises a pair of link elements pivotally connected to one another, one of which is mounted to the femoral cuff and the other of which is slidable relative to the tibial cuff along an axis substantially parallel to the longitudinal axis of the tibia of the leg of a patient to prevent forces from being applied to the knee by the brace except in the anterior-posterior direction. The location of the hinge axis of the brace is adjustable relative to the flexion axis of the knee to impose an anterior or posterior force of variable magnitude on the tibia depending upon the ligament injury or deficiency.