Subject-specific three-dimensional finite element model of the human knee complex

Abstract

Knee Osteoarthritis (OA) is a common medical condition that necessitates primary care for 1 in 5 adults over the age of 45 only in the UK. This causes functional limitations and decreases the quality of life. The OA is a metabolically active process which involves all joint tissues, i.e. bone, synovium and muscle which causes some symptoms such as persistent knee pain, morning stiffness and reduced functional capabilities. Most of the disability observed in knee OA is mainly because of pain. This mechanism is usually intensified by daily activities and the pain can relax by rest. Therefore, clinicians are interested to analyse this vital component, while accessing the internal structures such as cartilage or the menisci which is impossible in-vivo. Therefore, computational image-based models are effective tools in order to analyse the biomechanical causes of the OA. In this study, a three-dimensional finite element (FE) model of a healthy knee was constructed, using scanned MRI data. Bones, articular cartilages, menisci, patella, patella tendon and all the relevant ligaments were included in the model in their bio-realistic structures. 3D gait measurements were analysed to define loading and boundary conditions. After validation, the 3D finite element model was used to analyse the possibility of osteoarthritis condition and degeneration within the menisci and knee cartilage tissues. It was shown that the medial region of cartilage layers and menisci in the knee joint sustain higher values of stress for the OA conditions, while for the healthy knee, the stresses are more evenly distributed across the cartilage. This suggests that any treatment for knee osteoarthritis should focus more on the medial region of the tibiofemoral cartilage. Furthermore, the analysis of varus condition was added to the developed OA model and the results showed that the varus condition can exacerbate the OA.