Aseptic joint inflammation will give rise to increased SF NGAL concentrations, as shown in horses after intraarticular injection of local analgesics [20] and in humans with osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, spondyloarthropathy, and psoriatic arthritis, but levels are substantially lower than in septic joints, which may help differentiate the two conditions [25,39,40]. This evidence concerns the gene LCN2 and rheumatoid arthritis.