A device for exercising a patient’s leg, including rehabilitating a patient’s knee joint following knee surgery is disclosed. The method is for releasing, from a surface of a base plate, immunoglobulin G antibody bound to the surface via protein A. The vent strap has opposite ends that are fixed when the protection device is in the deflated condition. If establishing the requested connection using a first source identifier would result in a per source limit associated with the source restricting service being exceeded with respect to the first source identifier, a second source identifier is instead used to establish the requested connection. Those of the operating devices capable of operating as a central controller have stores for storing power-on data so that in the event of the current central controller becoming de-energised an arbitration process is invoked whereby the operating device having the best power-on history becomes the new central controller. This cuts the influence of expansion by half.