A modular knee system having various distal posterior femoral components that are interchangeable with each other and with various patellar-femoral joint components. The pallet includes a base for supporting the platform and its cargo. The armrest includes an upper part, which in the active position is positioned with its longitudinal axis substantially parallel to a substantially vertical plane through a side surface constituting an outer edge surface of the vehicle seat and intended to support a user’s forearm, and at least one lower part provided with a fixing device for attaching the upper part to the vehicle seat. A gain of the servo loop is adjusted as a function of the servo loop gain error signal in real-time. Two of the locking members include ramps extending radially outwardly to contact the body portion defining the entrance opening sequentially prior to contact by the locking arms of the other locking members.