title: Biomechanics of the knee joint in deep flexion: a prelude to a total knee replacement that allows for maximum flexion.
abstract: A two-dimensional anatomically based mathematical model of the human knee joint was developed to understand its biomechanics in deep flexion. The model was used to determine the internal knee loads as it simulates isometric quadriceps and hamstring co-contractions at different flexion angles during deep squat. It was found that in order to achieve deep flexion, large muscle forces are required, resulting in large tibio-femoral contact forces. In deep flexion, the femoral contact point was located on the most proximal point of the posterior condyle, location which was not affected by the level of quad activation. Conversely, the location of the tibial contact point was highly affected by the level of quad activation. Both anterior and posterior fiber bundles of the posterior cruciate ligament were found to carry high loads when the knee is maximally flexed. These results point to the important role of the posterior cruciate ligament in this position, and suggest the necessity of retaining this ligament during total knee replacement (TKR) procedures that allows for maximum flexion angles. Furthermore, the present data provide an explanation why most TKR's do not allow deep flexion: while contact occurs on the most proximal points of the posterior condyles in normal knees, this portion of the condyles is not presently resurfaced when performing a TKR.
authors.affiliation: Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH 43606, USA.
authors.forename: Christian E
authors.initials: CE
authors.lastname: Spanu
authors.forename: Mohamed Samir
authors.initials: MS
authors.lastname: Hefzy
mesh_terms: D000328:Adult; D000465:Algorithms; D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D005269:Femur / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008023:Ligaments, Articular / Q000502:physiology; D008297:Male; D008954:Models, Biological; D009068:Movement; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology; D013977:Tibia / Q000502:physiology; D016474:Weight-Bearing