We previously reported that heparan sulfate 6-O endosulfatases (Sulfs) were expressed in articular cartilage, and that the Sulf-1 knockout mouse developed severe knee osteoarthritis. In this study, we hypothesised that intra-articular injection of Sulf-1 would prevent cartilage degeneration. After confirming that 1 mg/ml Sulf-1 did not induce ATDC5 cell death in vitro, gene expression of type II collagen and matrix metalloproteinase (MMP)-13 in the presence of Sulf-1 (1-100 ng/ml) were determined by quantitative real-time polymerase chain reaction. Sulf-1 was also injected intra-articularly into mice following surgical destabilisation of the medial meniscus to produce a model of osteoarthritis, and cartilage degeneration was evaluated by safranin O and MMP-13 staining. We also investigated fibroblast growth factor 2 (FGF2)/extracellular signal-regulated kinase (Erk) cell signalling by western blotting. Exposure to Sulf-1 in vitro increased type II collagen expression and decreased MMP-13 expression in a concentration-dependent manner. Sulf-1 injection into the mouse osteoarthritic knee significantly suppressed glycosaminoglycan loss and MMP-13 expression. Erk1/2 signalling pathway activation was significantly reduced by Sulf-1 and FGF2. These findings indicate that Sulf-1 prevents cartilage degeneration by suppressing MMP-13 via an effect on FGF2/Erk1/2 signalling.