A marker-free video measurement and image processing method that provides numerical estimation of the 2-D centre of rotation of one rigid segment is tested. The algorithm is based on binary region moment features. A comparison is made between this method and a marker-based one, where the location of the markers has been calculated in two ways. The algorithm is also extended to handle two rigid segments. The method is to be applied in human locomotion analysis in order to calculate the centre of rotation of the hip joint. It's accuracy has been tested by a comparison with in vivo radiological measurements on humans.