Table 1.

Characteristics of the included SRs/MAs.

Author, year (country)	Trials (subjects)	Intervention group	Control group	Quality assessment	Main results
Raveendhara R. 2018 (USA) [26]	7 (769)	Curcumin	CT, placebo	Cochrane	Curcumin compounds can be a valuable supplement to the pharmacological treatment of OA in relieving pain, improving physical function, and reducing the risk of adverse events.
James W. Daily 2016 (South Korea) [34]	8 (892)	Curcumin, curcuma longa extract	CT, placebo	Cochrane	Compared with placebo, turmeric/curcumin can significantly reduce the VAS and WOMAC scores of OA patients. Compared with analgesics, the VAS scores of turmeric/curcumin and the control group were not significantly different, and there was no significant difference in the occurrence of adverse events.
An-Fang Hsiao 2021 (China) [28]	11 (1,258)	Curcumin	CT, placebo	Cochrane	Curcumin compounds were significantly better than the control drugs in the VAS score and WOMAC pain score, and there was no significant difference in the occurrence of adverse events.
Igho J. ONAKPOYA 2017 (UK) [32]	7 (797)	Curcumin	CT, placebo	Cochrane	Compared with placebo, curcuma longa extract has obvious effect in relieving pain and improving physical function. However, compared with NSAIDs, curcuma longa extract cannot improve stiffness and has less pain relief effect for patients with knee OA.
Zhiqiang Wang 2021 (Australia) [33]	10 (1,810)	Curcuma longa extract	CT, placebo	Cochrane	Compared with placebo, curcuma longa extract has obvious effect in relieving pain and improving physical function. However, compared with NSAIDs, curcuma longa extract has a higher level of safety for patients with knee OA.
Wenli Dai 2021 (China) [29]	10 (783)	Curcuma longa extract	Placebo	Cochrane	Compared with placebo, curcuma longa extract is more beneficial in relieving pain and improving the symptomatic OA, and there is no difference in the risk of adverse reactions.
Jian Wu 2019 (China) [30]	5 (599)	Curcumin, curcuma longa extract	CT, placebo	Cochrane	Curcumin can effectively treat patients with OA, improve WOMAC score and VAS score, and curcumin has no more side effects than ibuprofen.
Liuting Zeng 2021 (China) [31]	15 (1,621)	Curcumin, curcuma longa extract	CT, placebo	Cochrane	Both curcuma longa extract and curcumin can relieve pain and joint stiffness in patients with OA, improve joint function, and will not increase the occurrence of adverse events.
Weiyan Gong 2017 (China) [27]	6 (606)	Curcumin, curcuma longa extract	CT, placebo	Cochrane	Curcumin has the effect of treating OA without increasing gastrointestinal side effects