To investigate the relationship of circulating biomarkers of inflammation (C-reactive protein [CRP], interleukin-6 [IL-6], and YKL-40), angiogenesis (vascular endothelial growth factor), cartilage turnover (C-terminal crosslinking telopeptide of type II collagen [CTX-II], total aggrecan, matrix metalloproteinase 3 [MMP-3], and cartilage oligomeric matrix protein [COMP]), and bone turnover (CTX-I and osteocalcin) to inflammation on magnetic resonance imaging (MRI) and radiographic progression in patients with axial spondylarthritis (SpA) beginning tumor necrosis factor a (TNFa) inhibitor therapy.