A leg prosthesis adapted to a thigh stump includes an adapter (2) for a knee joint (3), a knee joint (3) mounted on this adapter, and a prosthetic lower leg (4) coupled to the knee joint (3). A prosthetic foot (5) is attached to this prosthetic lower leg and can pivot into a toes-raised foot position. The knee joint (3) upon transition from the extended position to the bent position performs a combined rolling-sliding movement about a pivot axis (6). A force-transmitting element (8) moves the prosthetic foot (5) substantially from the toes-down foot position to the toes-raised foot position during bending of the knee joint (3). Each bending position of the knee joint is transformed by a converter into an unambiguous electrical signal, which is supplied to a programmable control device, which generates a signal used to control an electrically adjustable actuator, which increases or decreases the resistance of the knee joint against or for further bending according to the signal.