The aim of this study was to determine stresses of the structures of the knee using the finite element method in patients with knee osteoarthritis with different Q angles. The study comprised 26 female patients with right knee osteoarthritis. The patients with the largest, the smallest and the median Q angle were selected. These Q angles were determined as 22 degrees, 15 degrees and 10 degrees, respectively. Computed Tomography and Magnetic Resonance Images of the right knee were then taken and made 3D using the Mimics 10.01 program. Bone and soft tissues of the knee joint were converted to a solid model using the SolidWorks program. Finally, physiological conditions appropriate to a standing position were applied and analyses were made with the Ansys Workbench program. When comparing the stresses in the cartilages of the patients with knee osteoarthritis with Q angles of 10 degrees, 15 degrees and 22 degrees, the highest stress value was found in the tibial cartilage and femoral cartilage of the patient with the 22 degrees Q angle and patellar cartilage of the patient with the 10 degrees Q angle. When comparing the stresses in the knee structures of the patients, the lowest stress was in the structures of the patient with the 15 degrees Q angle. According to our results, when there is a high or low Q angle, knee joint alignment deteriorates, which may adversely affect the osteoarthritis process increasing degeneration of the knee joint structures. Therefore, the Q angle should be taken into account in knee rehabilitation.