Mechanisms of Osteoarthritis (OA) Pain

Abstract

Purpose of ReviewOsteoarthritis (OA) is a major cause of pain and disability worldwide. There is, however, a relatively poor correlation between the severity of OA based on plain radiograph changes and symptoms. In this review, we consider the mechanisms of pain in OA.Recent FindingsIt is now widely recognised that OA is a disease of the whole joint. Data from large observational studies which have used magnetic resonance imaging (MRI) suggest that pain in OA is associated with a number of structural factors including the presence of bone marrow lesions (BMLs) and also synovitis. There is evidence also of alterations in nerve processing and that both peripheral and central nerve sensitisation may contribute to pain in OA.SummaryIdentification of the causes of pain in an individual patient may be of benefit in helping to better target with appropriate therapy to help reduce their symptoms and improve function.

The relationship between synovial inflammation, structural pathology, and pain in post-traumatic osteoarthritis: differential effect of stem cell and hyaluronan treatment

“…While incident and worsening pain in patients with knee OA is consistently associated with imaging measures of synovitis and effusion [2][3][4][5][6], the correlation between clinical symptoms and synovial biopsy histology in established disease is poor [49]. This may be driven by the focal nature of OA synovitis whereby lesions are missed in small biopsies.…”

“…Cartilage breakdown combined with its poor reparative capacity means that its loss in OA signifies "end-stage disease" and drives the need for joint replacement. However, numerous clinical studies have shown that incident and worsening pain in knee OA are much more strongly associated with subchondral bone marrow lesions and synovial inflammation/synovitis rather than with cartilage pathology [2][3][4][5]. Interestingly, synovitis, unlike bone marrow lesions, is also associated with neuropathylike pain sensitization in knee OA patients [6].…”

Patients Age is a Critical Factor in Determining the Severity of Osteoarthritis of the Shoulder

“…This discrepancy may also be explained by some aspects of the pathology of OA that are related to pain like synovitis or bone marrow edema that cannot be seen in X-ray imaging. 24 Additionally, periarticular pathologies such as subacromial bursitis and / or rotator cuff -and biceps tendinitis are also common in patients with shoulder OA resulting in local pain and not depicted in x-ray pictures. These numerous "nonarticular pain conditions" might also contribute to the discrepancy between pain intensity and the radiographic severity in the shoulder OA.…”

Hip Joint Osteoarthritis Pain Sources and Control

“…Unfortunately, one or more of these pain sources has the proclivity to foster nerve desensitization and prolonged firing in the diseased state [63], and a pain state that is often unchanged, despite hip joint replacement surgery [64]. This pain state may be quite diffuse in nature with certain areas of maximum intensity [65], while exhibiting features of neuropathic [66] as well as inflammatory pain [17] [51] [55] [67], along with episodes of ligamentous sprain with movement that provoke pain [6].…”