Previous studies have suggested that TGF-β1 synthesized by the ligamentum flavum fibroblasts increases collagen synthesis, resulting in hypertrophy.17-19) Therefore, it is suggested that increased fibrosis of the ligamentum flavum in spinal stenosis patients is a net result of a series of synthesis and destruction of the collagen fibers by TGF-β1 and MMP-13. The gene discussed is MMP13; the disease is spinal stenosis.