Ultrasonographic features in symptomatic osteoarthritis of the knee and relation with pain

Objective. Radiographic knee OA is moderately associated with pain. As OA is a disease of the entire joint, ultrasonography visualizing cartilage and soft tissue structures might provide more insight into the complex process of pain in knee OA. The objective of this study was to investigate the cross-sectional association between US findings and pain in knee OA. Methods. In this observational study, 180 patients fulfilling the ACR clinical criteria for knee OA underwent US examination of the most symptomatic knee. The US protocol comprised assessment of synovial hypertrophy, joint effusion, infrapatellar bursitis and Baker's cyst, medial meniscus protrusion and cartilage thickness. To evaluate the association between US features and pain (Numerated Rating Scale from 0 to 10 and the Knee Injury and Osteoarthritis Outcome Score pain subscale), regression analysis was performed. Results. In regression analysis, no association between US or clinical or demographic features and the level of knee pain was found. Conclusion. In this cohort, no association between US features and the degree of knee pain was found. Despite the attractiveness of US (easy accessible, inexpensive and no radiation involvement) and the fact that previous research suggested otherwise, it remains uncertain which part of pain in knee OA is explained by pathology in soft tissue structures and whether US of the knee is the imaging tool of choice to visualize this pathology.