In this study, extracts of Boswellia serrata gum resin, Curcuma longa rhizome, and Terminalia chebula fruit were combined in different ratios, and their anti-osteoarthritis effects were compared to determine which combination had the best synergistic effect. B. serrata, C. longa, and T. chebula extracts in a 2:1:2 ratio exhibited higher antioxidative activity in scavenging DPPH radicals than did the individual extracts alone or the other extract combinations. Additionally, the 2:1:2 combination significantly improved the levels of enzymatic antioxidants and antioxidant-related proteins. Moreover, this same combination ratio decreased the protein levels of matrix metalloproteinase (MMP) 3 and MMP13 in interleukin-1β-stimulated human articular chondrocytes (HCHs) and increased those of aggrecan and collagen type II alpha 1 chain (COL2A1). Analysis of the underlying mechanisms revealed that the 2:1:2 combination significantly inhibited the phosphorylation of nuclear factor kappa B (NF-κB) p65, extracellular regulated protein kinase (ERK), and p38 mitogen-activated protein kinase (MAPK). Therefore, the 2:1:2 combination of these three plant extracts has the best potential for use as an effective dietary supplement for improving joint health compared with the individual extracts and t...