In recent years, with the increased understanding of chronic disease processes such as knee osteoarthritis (KOA), the biopsychosocial approach has received emphasis as a form of treatment for these diseases. In this approach, many factors can influence the individual's physical performance, such as demographic, anthropometric, and psychological factors. However, the significant association of psychological factors with physical performance is still uncertain, as psychological factors are significantly associated both with self-reported and objective physical performance and with pain, the latter being also a determinant of low self-reported and objective physical performance.

To examine whether psychological aspects predict low self-reported and objective physical performance in individuals with KOA, considering the effect of age, body mass index and pain.

Ninety-eight individuals (mean ± SD = 63.2 ± 8.4 years, 72 women) with KOA participated in the study. Eligibility criteria for participation in the study were age over 50 years, knee pain for more than six months, and diagnosis of KOA according to the American College of Rheumatology criteria. The diagnosis should be accompanied by radiological evidence, affecting one or more compartments of the knee, at a mild, moderate or severe level, being unilateral or bilateral according to the Kellgren and Lawrence criteria. In addition, they should also present a level ≥3 of pain. The main assessment measures were Numerical Pain Scale, Pressure Pain Threshold, Beck Depression Inventory (BDI), Pain Catastrophizing Scale (PCS), Western Ontario and McMaster Universities Osteoarthritis Questionnaire (WOMAC) and Gait Speed.

The different regression models revealed that the pain dimension of the WOMAC was the most significant measure of pain intensity to predict poor physical performance. Furthermore, it has been demonstrated that pain catastrophizing (PCS) is the most significant psychological measure to predict low self-reported physical performance and depressive symptoms (BDI) to predict low objective physical performance.

There is an association between psychological factors, pain, and physical performance in individuals with KOA, with pain catastrophizing being the psychological measure best predicting low self-reported physical performance, whereas depressive symptoms predict low objective physical performance.

Bearing in mind that psychological factors have a significant influence on the symptomatology of individuals with KOA, mainly regarding pain and physical performance, this study reveals the need for a psychosocial approach in the clinical management of the disease.