Osteoarthritis is a degenerative disorder affecting every tissue within the joint. OA is characterized by the degeneration of articular cartilage leading to inflammation of the underlying bone and synovium, resulting in loss of mobility and pain. Inflammation has been shown to play a key role in the development and progression of OA, but since OA is a multi-factorial disease, its exact pathogenesis has yet to be fully elucidated. However, it has been established that a major influence in the development of OA is the presence of pro-inflammatory cytokines in the synovium; specifically, IL-1-beta has been implicated in cartilage destruction and the TNF pathway in the OA inflammatory cascade. The ability to detect these cytokines is limited until progression of the disease is relatively advanced.
To date, few studies have examined the cellular composition (including inflammatory cells) in the synovium of patients with early OA. Furthermore, in studies which do examine cells within the synovium, few if any compare these results to stringently characterized normal joints.
The current study examined human synovium taken from OA patients at the time of arthroscopic knee surgery, while normal tissue was harvested from cadaveric donations. Synovium was taken from one to four sites within the joint (osteoarthritic and non-osteoarthritic (normal) human knees) and examined using histological techniques to determine the cellular composition of the synovium. Within joint and between joint comparisons were made. There were no significant trends found either within joint or between joint with regards to cellularity. Early OA synovium was defined as subclinical OA synovium; this being the case, the lack of significant difference could be due to the fact that early OA synovium has few differences from “normal synovium”.