A leg support exoskeleton is strapped on as wearable device to support its user during squatting. The exoskeleton includes a knee joint connected to a first line and a second link, which is configured to allow flexion and extension motion between the first link and the second link. A force generator has a first end that is rotatably connected to the first link. A constraining mechanism is connected to the second link and has at least two operational positions. In a first operational position, the second end of the force generator engages the constraining mechanism, where the first link and the second link flex relative to each other. In a second operational position, the second end of the force generator does not engage the constraining mechanism; the first link and the second link are free to flex and extend relative to each other.