Inflammation & Immunity

Concurrent Session 12

Date/Time: Sunday, May 3, 2020 - 8:45 AM to 10:15 AM
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The Role of Synovium in the Onset and Progression of OA

Conventionally, the synovial changes in OA are considered to be a secondary event associated with cartilage degeneration. However, recent studies have shown that synovial changes are actively involved in the pathology of OA. This presentation provides an overview of our current understanding of the synovial changes in knee OA.

Clinically, the significance of synovial changes in OA is two-fold. First, synovial changes are closely related to the symptoms of knee OA, especially pain. Studies using MRI have revealed that the presence of effusion-synovitis in knee joints is associated with knee pain. Second, synovial changes may be related to the structural progression of knee OA. The results of cohort studies have consistently indicated that knees with effusion-synovitis are at higher risk for disease progression. Thus, synovial changes may play a pivotal role in the pathology of OA by causing pain and cartilage degeneration.

The severity of synovial changes in OA joints may change with time. This may explain some of the clinical features of OA. For example, the symptoms of knee OA may fluctuate with time, and the progression of OA is often phasic. These features may be related to the vacillation of synovial changes. Synovial changes may occur irrespective of the severity of structural changes observed on radiographs. Again, this may explain the dissociation between the extent of structural changes and the severity of symptoms which is often encountered with the disease.

While most of the above findings were obtained from observations of established OA, recent studies have focused on the knee joints in the very early stage of the disease, or early OA, in an attempt to elucidate the initial change(s) that may trigger the disease. The results of such studies have shown that the synovial changes may occur prior to the development of radiographic changes, and that such changes may cause pain and structural changes in the joints of early OA patients, as occurs in established OA. Thus, synovial changes may be an initial event of OA, which plays a key role in the initiation of the disease.

Despite its significance, the mechanism(s) underlying synovial changes in OA has not yet been elucidated. Again, it is not known why synovial changes are related to pain or structural progression. It is therefore necessary to elucidate the mechanism(s) underlying the synovial change in OA since it will be helpful to establish effective treatments for knee OA.