A patient support apparatus comprising a patient supporting surface including a number of bladders (182, 184, 186, 188, 190, 192, 194, 196, 198, 200) organized into a plurality of zones (202, 204, 206, 208, 210), a plurality of pressure sensors (222, 224, 226, 228, 230), each pressure sensor (222, 224, 226, 228, 230) operable to measure a pressure in a respective zone (202, 204, 206, 208, 210), a user interface including a display and a number of user inputs, and a controller in communication with the pressure sensors (222, 224, 226, 228, 230) for receiving data signals indicative of the pressure in each of the zones (202, 204, 206, 208, 210), the controller adapted to process the data signals from the pressure sensors (222, 224, 226, 228, 230), wherein the controller is adapted to process the data signals to determine a measure of mobility of a patient supported on the patient supporting surface, characterised in that the processing of the data to determine the measure of mobility includes determining a mobility index for each of the plurality of zones for a predetermined time period and summing each of the mobility indices to arrive at a mobility score, the mobility indices being determined by one of: integrating the differences between an actual pressure measured and a nominal pressure over a predetermined period, the nominal pressure being the pressure with no movement as determined from an initial condition or a long running average; and determining the work transferred from the person supported on the patient supporting surface to the patient supporting surface. a plurality of pressure sensors (222, 224, 226, 228, 230), each pressure sensor (222, 224, 226, 228, 230) operable to measure a pressure in a respective zone (202, 204, 206, 208, 210), a user interface including a display and a number of user inputs, and a controller in communication with the pressure sensors (222, 224, 226, 228, 230) for receiving data signals indicative of the pressure in each of the zones (202, 204, 206, 208, 210), the controller adapted to process the data signals from the pressure sensors (222, 224, 226, 228, 230), wherein the controller is adapted to process the data signals to determine a measure of mobility of a patient supported on the patient supporting surface, characterised in that the processing of the data to determine the measure of mobility includes determining a mobility index for each of the plurality of zones for a predetermined time period and summing each of the mobility indices to arrive at a mobility score, the mobility indices being determined by one of: integrating the differences between an actual pressure measured and a nominal pressure over a predetermined period, the nominal pressure being the pressure with no movement as determined from an initial condition or a long running average; and determining the work transferred from the person supported on the patient supporting surface to the patient supporting surface. integrating the differences between an actual pressure measured and a nominal pressure over a predetermined period, the nominal pressure being the pressure with no movement as determined from an initial condition or a long running average; and determining the work transferred from the person supported on the patient supporting surface to the patient supporting surface.