The inclusion criteria for all participants were being between 18-65 yy.  The inclusion criteria for RA patients were: confirmed diagnosis of RA according to 2010 ACR/EULAR classification criteria and lack of any other inflammatory articular diseases.  The inclusion criteria for knee OA patients were: diagnosis according to ACR classification criteria of knee OA with grade 2-3 according to the Kellgren-Lawrence grading system and lack of any other inflammatory articular diseases.  Volunteers who did not have any knee pain, no clinical degenerative or inflammatory signs were included in the healthy control group.  -  Exclusion criteria for all participants were: being out of age range, history of knee joint trauma, surgery or knee joint injection in the previous 6 months, presence of any other disease that can affect thigh muscles (radiculopathy, myopathy, hip problems). Patients with secondary knee OA were not included.  -