Abstract: A prosthesis for lower-limb amputees having a foot segment and a tibial segment pivotally connected to each other about an articulation axis that perform an ankle joint of a leg/foot prosthesis. The leg-foot prosthesis has a gear motor whose axis coincides with the axis of the tibia. From the gear motor a pinion gear extends below with conical toothed shape that meshes with a toothed arch present on the foot. This way, the gear motor operates the relative movement between tibia and foot and varies the relative angle ?. The gear motor can be associated with a microprocessor that is adapted to control the movement of the ankle joint. To obtain that, the microprocessor communicates with a position transducer provided at the articulation axis of the ankle that measure the rotation of the ankle, i.e. the angle ?.