ESTIMATION OF THE KNEE-JOINT LOCATION USING COLOR VIDEO

Analysis of the knee joint moment might be useful for predicting the r isk of prosthetic loosening. The moment can be estimated if the locati on of the centre of pressure in the knee joint and the ground reaction force vector are known. Usually, skin mounted markers are used to loc ate the knee joint centre. Since marker based methods have several dra wbacks investigations of alternative methods are needed. A new method for location of the knee joint is outlined in this paper. The subject is video filmed during gait with an elastic blue band wrapped around t he knee. The band is located by splitting the video images into the RG B-components, and the centroid of the band is used as an estimate of t he knee joint centre location. The band is easier to mount than marker s, and it is not sensitive for axial leg rotation like markers are, wh ich simplifies the analysis. If desired, the axial leg rotation can be determined by attaching a circular cyan marker on the band. The centr oid of the marker relative to the band centroid gives an approximation of the leg rotation. In this study, the band could easily be located in the images and the leg axial rotation estimated in the frontal and the sagittal view showed the same trend. Further, the band-based resul ts were found to be comparable to results where a marker was used to l ocate the knee joint centre. (C) 1997 Elsevier Science Ireland Ltd.