IL1B and rheumatoid arthritis: Though a characteristic of OA, the use of inflammatory cytokines such as IL-1β and TNF-α to induce a chondrocyte disease state is more appropriate to the study of rheumatoid arthritis (RA), not OA [20–24]. And, while mechanical disruption using high strain dynamic loading (up to 25% at 1 Hz) has been shown to induce OA-like cell responses in MSC-laden hydrogel [19], these models do not generate the etiology of PTOA because they do not use acute loads to initiate the onset of OA.