Objective To investigate the role of growth arrest DNA damage-inducible gene 45beta (GADD45β) in the development and mechanism of osteoarthritis (OA). Methods Rat chondrocytes were divided into control group, interleukin-1β (IL-1β) group, NC-OE+IL-1β group, GADD45β OE+IL-1β group, NC-sh+IL-1β group and GADD45β sh+IL-1β group. Except the control group, cells in other groups were treated with 10 ng/mL IL-1β for 24 h. Chondrocyte proliferation and apoptosis were detected by MTT and TUNEL methods. Rats were divided into Sham group, OA group, NC-OE+OA group and GADD45β OE+OA group (n=12). Rats in sham group undergoing sham operation, and rats in other group were OA model rats induced by anterior cruciate ligament amputation and medial meniscectomy. Phosphate buffer was injected into the joint cavity of Sham group and OA group. NC-OE and GADD45β OE+OA lentivirus were injected into the joint cavity of NC-OE and GADD45β OE+OA group, respectively. The injection was given once a week for 4 weeks. The cartilage degradation was observed by safranin O - fast green staining and OARSI score was performed. Chondrocyte apoptosis was detected by TUNEL staining. mRNA levels of GADD45β, B-cell lymphoma/leukemia-2 (Bcl-2), Bcl-2 associated X protein (Bax), matrix metalloproteinase (MMP) 3, MMP13, IL-1β, IL-6, and tumor necrosis factor-α (TNF-α) were detected by RT-qPCR. Protein levels of GADD45β, mitogen-activated protein kinase kinase 7 (MKK7), p-MKK-7, c-Jun amino-terminal kinase (JNK) 1/2/3 and p-JNK1/2/3 were detected by Western blot.Results Compared with control group, the mRNA and protein levels of GADD45β decreased in IL-1β group (P＜0.05), the relative cell viability and Bcl-2 mRNA levels decreased (P＜0.05), TUNEL positive rate and the mRNA levels of Bax, MMP3, MMP13, IL-1β, IL-6 and TNF-α increased (P＜0.05), and the relative phosphorylation levels of MKK-7 and JNK1/2/3 increased (P＜0.05). Compared with IL-1β group and NC-OE+IL-1β group, the mRNA and protein levels of GADD45β increased in GADD45β OE+IL-1β group (P＜0.05), the relative cell viability and Bcl-2 mRNA levels increased (P＜0.05), TUNEL positive rate and the mRNA levels of Bax, MMP3, MMP13, IL-1β, IL-6 and TNF-α decreased (P＜0.05), and the relative phosphorylation levels of MKK-7 and JNK1/2/3 decreased (P＜0.05). Compared with IL-1β group and NC-sh+IL-1β group, the mRNA and protein levels of GADD45β decreased in GADD45β sh+IL-1β group (P＜0.05), the relative cell viability and Bcl-2 mRNA levels decreased (P＜0.05), TUNEL positive rate and the mRNA levels of Bax, MMP3, MMP13, IL-1β, IL-6 and TNF-α increased (P＜0.05), and the relative phosphorylation levels of MKK-7 and JNK1/2/3 increased (P＜0.05).Compared with sham group, the mRNA and protein levels of GADD45β decreased in OA group (P＜0.05), Bcl-2 mRNA levels decreased (P＜0.05), OARSI score and TUNEL positive rate increased (P＜0.05), the mRNA levels of Bax, MMP3, MMP13, IL-1β, IL-6 and TNF-α increased (P＜0.05), and the relative phosphorylation levels of MKK-7 and JNK1/2/3 increased (P＜0.05). Compared with OA group and NC-OE+OA group, the mRNA and protein levels of GADD45β increased in GADD45β OE+OA group (P＜0.05), Bcl-2 mRNA levels increased (P＜0.05), OARSI score and TUNEL positive rate decreased (P＜0.05), the mRNA levels of Bax, MMP3, MMP13, IL-1β, IL-6 and TNF-α decreased (P＜0.05), and the relative phosphorylation levels of MKK-7 and JNK1/2/3 decreased (P＜0.05). Conclusion GADD45β is down-regulated in OA, and up-regulated GADD45β may inhibit OA progression by inhibiting MKK7/JNK pathway