GROUND REACTION FORCE AND ITS MOMENT WITH RESPECT TO THE KNEE-JOINT CENTER IN A TOTAL CONDYLAR ARTHROPLASTY SERIES

In a group of patients with rheumatoid arthritis (n = 5) and osteoarth rosis (n = 3) who had had 12 total condylar knee arthroplasties a new technique for assessment of ground reaction forces was used. This tech nique graphically displays force vectors superimposed in real time on a video recording of the subject walking. We found that this new techn ique could assess reliably moments of the ground reaction force vector s with respect to the centre of the knee joint. Four patients had bila teral total condylar knee arthroplasty. All patients were subjectively satisfied with their operations and had neither radiographic nor clin ical signs of loosening. Considerable moments were found in the dorsal part of the medial tibiofemoral compartment. These moments increased with extension deficits and varus angles. The size of these moments we re consistent with earlier findings of increased bone strengths in the same compartment as the biological answer to stress demands and earli er studies of moment after total condylar knee arthroplasty.