Purpose: To explain the variance in knee pain and perceived need for surgery (PNS) using psychological measurements of depression, anxiety and stress symptoms, physical activity, Body Mass Index (BMI) and Waist Circumference (WC) in obese and non-obese individuals with knee osteoarthritis (OA). Methods: Participants were a sample of 31 women and men between 50 and 80 years old diagnosed with knee OA, based upon radiographic examination evaluated by an orthopedic surgeon, were pre-selected. Three different methods of radiographic examination (Kellgren and Lawrence, Ahlback and Cooke) were used to detect differences between groups. Depression was assessed using the Beck Depression Inventory (BDI). The BDI is a 21-item self-report instrument intended to assess the existence and severity of symptoms of depression. Depression, Anxiety and Stress Scale (DASS) was also used. The DASS is a 42-item self-report questionnaire divided in three scales designed to measure the negative emotional states of depression, anxiety and stress. Physical Activity (PA) was assessed using Metabolic Equivalents (METs) values of common physical activities classified as light, moderate and vigorous intensity activity based on guidelines for exercise testing and prescription of the American College of Sports Medicine (ACSM). Knee pain and PNS were assessed using a visual analog scale (VAS) after performance testes, such as 6 Minute Walk Test, Timed Up and Go, stairs climbing test and peak of oxygen consumption, had been performed. Participants were asked to score by pointing on a 10 cm line (0-10) their perceived level of knee pain. Likewise for PNS, participants were asked to indicate under the same scale their perceived need for surgery. Results: Participants were divided according to their BMI into two groups: obese and morbid obese individuals (BMI = 30 kg/m2; > 35 kg/ m2) or group A (N = 15) and healthy weight and overweight individuals (BMI = 18.5-24.9 kg/m2; BMI = 25-29.9 kg/m2) or group B (N = 16). An independent t-test between groups did not show any significant difference in radiographic OA, indicating that both groups had similar levels of knee OA severity. Our two correlation analysis between knee pain and radiographic OA and between PNS and radiographic OA did not show any significant correlation. Multiple Regression Analysis, from a sample of 31individuals, indicated that BDI had the highest correlation with PNS (r = .71; p < .0001) and the coefficient of determination (R2) of the model was R2 = .62 (p < .0001). Our second Multiple Regression Analysis used a sample of 46 individuals including group A (N = 15), group B (N = 16) and healthy controls (N = 15). While excessive weight measured by BMI and Waist Circumference showed strong and significant correlations (r = .64; p < .0001) and (r = .69; p < .0001) with knee pain, our results indicated again that BDI had the highest correlation with knee pain (r = .77; p < .0001) and the coefficient of determination of the model was R2 = .75 (p < .0001). Conclusion: Notwithstanding the importance of radiographic findings to diagnose knee OA, our study did not show any significant correlation between radiographic OA and knee pain and PNS. Knee pain, due to OA, is the predominant symptom of OA and is the general reason why people decide to undergo total knee replacement surgery. Our study emphasizes the relevance of a more comprehensive understanding of pain complaints to improve our ability to identify individuals with knee OA and to apply rational treatment strategies, thereby offering a relevant target for intervention.
Coriolano, K., Harrison, M., Aiken, A., & Pukall, C. (2014). In order to explain knee pain due to osteoarthritis, should we start looking for answers outside of the knee joint? Osteoarthritis and Cartilage, 22, S405. https://doi.org/10.1016/j.joca.2014.02.760