TNF and Obesity: Interleukin-1β (IL-1β) and tumor necrosis factor-α (TNFα) are two important inflammatory cytokines that not only lead to cartilage matrix destruction, but also prevent chondrogenic differentiation of mesenchymal stem cells.115 These cytokines can be systemically upregulated, or produced by synoviocytes, chondrocytes, or meniscal cells.116 Also, co-morbidities, such as obesity, can elevate levels of pro-inflammatory cytokines, exacerbating the effects of a joint injury.117