Green tea is known as a dietary supplement and a novel functional food worldwide. Since there are increasing preclinical evidence about efficacy of green tea for treating osteoarthritis, this study has aimed at assessing its efficacy and safety for patients with knee osteoarthritis.
This is a randomized open-label active-controlled clinical trial. As many as fifty adults with osteoarthritis of knee were randomly allocated to receive the green tea extract (in dosage form of tablet) plus diclofenac tablet as "intervention group"; or: diclofenac tablet alone as "control group" for a period of four weeks. Patients were assessed at the beginning of intervention, and then 4 weeks later, in terms of pain score via visual analogue scale (VAS), and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire's total score in addition to its 3 sub-scores. Furthermore, they were asked about any adverse effects during intervention period.
Mean differences of VAS pain, total WOMAC, and WOMAC physical function scores in green tea group showed a significant reduction, compared with the control group (P = 0.038, P = 0.006, and P = 0.004, respectively). However, No significant differences between the two groups were observed, regarding mean differences of WOMAC pain and stiffness scores of the enrolled patients (P = 0.163, and P = 0.150, respectively). Additionally, only 1 patient reported gastric upset [in control group].
It seems that green tea extract might well be considered as an adjunctive treatment both for control of pain and for the betterment of knee joint physical function in adults with osteoarthritis. However, further studies of longer duration and larger sample size are needed.