We studied the familiarisation time required for reliable sagittal-plane knee kinematics and temporal-distance gait measurements to be obtained from treadmill walking. We also studied whether knee kinematics and temporal-distance gait measurements obtained from familiarised treadmill walking can be generalised to overground walking. Sixteen subjects without pathology walked on a level overground walkway and on a treadmill. A motion measurement system was used to measure sagittal plane knee movements and temporal-distance gait parameters during overground and treadmill walking. Highly reliable knee kinematics and temporal-distance gait measurements [intraclass correlation coefficient (ICC)(2,1)>/=0.93] were found after 6 min of treadmill walking. These measurements, obtained after 6 min of treadmill walking, were highly correlated with and not significantly different to those of overground walking. Reliable measurements that can be generalised to overground walking, can be obtained from the treadmill within a familiarisation time of 6 min.