KINEMATICS OF THE KNEE-JOINT IN DEEP FLEXION - A RADIOGRAPHIC ASSESSMENT

The purpose of this study is to describe the kinematics of normal knee s in vivo. assessed in deep flexion, using bi-planar radiographs. Ante ro-posterior and lateral views were obtained from five healthy males d uring three sequential positions of kneeling. In the first position, t he subject knelt with the knees fully flexed (deep flexion between 150 and 165 degrees) and torso upright. In the second position, the subje ct bowed forward to an intermediate position (about 120 degrees of kne e flexion). In the third position, the subject bowed further until his head touched the floor, supporting the upper torso with hands and wit h the knees flexed at about 90 degrees. The results show that past 135 degrees of knee flexion, the patella cleared the femoral groove and w as in contact only with the condyIes. For these particular postures, a nd during deep flexion, motion of the femur on the tibia did not revea l the classical femoral 'roll back'. Rather the lateral femoral condyl e rolled further over the postero medial aspect of the lateral tibial plateau while contact of the medial femoral condyle occurred more ante riorly, but still in the posterior part of the medial plateau. This as ymmetric rolling motion indicated an element of internal tibial rotati on. Furthermore, the tibia was found to articulate with the femur at t he most proximal points of the condyles in deep flexion. These data on the kinematics and contact characteristics of the tibio-femoral joint must be considered in any approach to design for a Deep Flexion Knee implant. (C) 1998 IPEM. Published by Elsevier Science Ltd. All rights reserved.