Osteoarthritis of the Knee as One of the Major Musculoskeletal Diseases Responsible for Locomotive Syndrome: The Role of Synovitis in Pain

Abstract

Osteoarthritis of the knee (knee OA) is an increasingly important public health concern, as the prevalence of the disease is increasing with the aging of society. It is considered to be one of the major diseases responsible for locomotive syndrome, defined as being restricted in one’s ability to walk owing to a dysfunction in one or more parts of the locomotion system. However, as no disease-modifying treatments for knee OA exist, all of the currently available treatments are symptom-modifying. Pain is the most prominent and disabling symptom of OA, and is also one of the factors predicting the progression of OA. There is an urgent need to improve our understanding of both the pathophysiology and the symptoms of the disease. Recently, the role of synovitis in OA has attracted particular attention, as synovitis has been revealed to be one of the potential indicators of knee pain and a predictive factor for both structural and symptomatic progression of the disease. In this review, we introduce the associations among pain, symptoms, and synovitis in patients from early- to end-stage knee OA, and also address future perspectives regarding the involvement of synovitis in the management of knee OA.