Recovering from serious leg injuries can take a lot of time. In ComEx Knee-Ankle Exoskeleton, we have a powered knee-ankle orthosis with a modular actuator, frameless components and light materials. The 4.56 kg wearable features torque control for walking at different speeds. Here is what the researchers had to say about this:
A human subject experiment demonstrates accurate torque control with high output torque during stance and low backdrive torque during swing at fast walking speeds. This work shows that backdrivability, precise torque control, high torque output, and light weight can be achieved in a powered orthosis without the high cost and complexity of variable transmissions, clutches, and/or series elastic components.
Bionic Locomotion has shared more info here.