The importance of objectively measuring functional tests in complement to self-report assessments in patients with knee osteoarthritis

•Functional tests (FT), should be used as complementary tools.•FT are relevant to measure of the knee OA patients performance treated with PRP.•Results suggest caution by using only self report measurement in clinical trials. Osteoarthritis (OA) is a chronic degenerative disease which can result in chronic pain, loss of joint function and consequently decline in quality of life. A variety of instruments that measure the different dimensions of health status in patients with OA are available. However, despite the fact that WOMAC and other questionnaires and scales may provide additional understanding regarding the patient’s condition, some studies have reported discrepancies between patients’ perceptions and their actual ability to perform the task. The aim of the present study was investigate the physical capabilities with the function domain of WOMAC. This study has a cross-sectional design including patients diagnosed with moderate to severe knee OA (i.e., grades II, III and IV) according to the Kellgren-Lawrence. These patients were submitted to the battery of functional tests recommended by the OARSI group (30-second chair stand test, 40 m fast paced walking test, Stair climb test, timed “Up and Go”, and Six-minute walking test) and filled the WOMAC. Pearson’s correlation and multiple linear regression was applied. A total of 153 patients were included. A significant and weak correlation was observed between WOMAC and the 40-meter walking test, TUG, stair-climbing test, and the 6MWT. In addition, 30-second chair stand test demonstrated a significant and moderate correlation (r=-0.503). The multiple regression analysis results indicated that only 30-second chair stand test was a significant (p = 0.001) predictor of WOMAC. This result remains significant even after adjusting for age, BMI, total muscle mass, and number of knees affected The 30-second chair stand test is associated with the WOMAC function domain. There is no correlation of this domain with any other functional tests, emphasizing the importance of including other tests for a global evaluation.