A Finite Element Analysis for the assessment of Tibial Internal and External Rotation: effects in Healthy Knee

The knee represents the biggest and most complex human joint and still nowadays many aspects related to the maintenance of its functionality need to be investigated. The wear of the cartilage part could bring to a disease known as osteoarthritis that provoke knee pain which can be related to the femoral-tibial misalignment. This disease can be treated with the use of prostheses to restore the normal knee function. However, it is known that the misalignment of the prosthetic components can cause greater wear of the polyethylene insert, thus leading to an early revision. Moreover, it has been observed that patients with tibia internal rotation had a correlation with the development of osteoarthritis. Finally, it has been seen that elderly people with healthy knee present instead a tibia external rotation. Until now, no studies have been conducted on different femoral-tibial torsion configurations in healthy knee. For this reason, the current study aims to develop and compare two healthy knee models that present respectively a femoral-tibial torsion of -11° and 0°, by means of Finite Element Analysis (FEA). Therefore, the purpose is to determine if in a virtual knee prototype the internal rotation of the tibia causes higher stress values during flexion. The results seem to be promising, in fact it has been found that the internal rotation of the tibia causes greater stress in the menisci, in particular in the medial part. Despite the stress in the tibia appears to be greater in the tibia external rotation case, this seems to be spread over a more extensive area in the internal rotation case which is also comparable with the wear present in a real tibia with osteoarthritis (OA). Thus, this seems to confirm the correlation between the internal rotation of the tibia with OA development. It can be concluded that the finite element model employed in this work can study the effects that different femoral-tibial torsion conditions provoke on the knee. Thus, this study can be considered as a first step towards new research that aims to computationally determine the benefits that preventive osteotomy could bring.