The jury is still out on the effectiveness of curcumin (turmeric supplements) in reducing the symptoms of knee osteoarthritis, despite some small signals from a recent pilot study.
The Tasmanian RCT randomised 70 patients with symptomatic knee OA and effusion synovitis to either Curcuma longa (CL) extract or placebo for 12 weeks.
It found knee pain reported on a visual analogue scale (VAS) improved more in the people taking the supplement than those on placebo (24 v 14 points; p=0.039).
However in the other primary outcome, there was no significant difference between the groups in the change in MRI-assessed effusion–synovitis volume.
Secondary outcomes showed curcumin improved WOMAC scores for pain and function compared to placebo.
The percentage of OARSI-OMERACT responders in the treated group was also higher than the control group (62.9% v 38.2%; p = 0.035).
No differences were seen in other measures including T2 relaxation time of lateral femoral cartilage, AQoL-derived utility, or physical function assessed by performance measures such as chair stand repetitions, walking pace and stair climbing.
“Compared with placebo, CL modestly but statistically significantly reduced knee pain over 12 weeks, as assessed by both VAS and WOMAC, with no increase in adverse events; however, it did not change effusion–synovitis volume or cartilage composition as assessed by MRI,” the study said.
“We observed an effect of 9.1 mm between the treatment groups, which is a modest effect size for pain reduction, but of a magnitude smaller than the minimal clinically important difference (18 mm) for which the study was powered. Therefore, the modest pain reduction in this study may be of uncertain clinical importance.”
“Multicentre trials with larger sample sizes are needed to assess the clinical significance of these findings.”
Professor Kim Bennell, co-chair of the working group for the national Guideline for the management of knee and hip osteoarthritis, told the limbic the study’s findings were consistent with the neutral recommendation in the guidelines.
“We are unable to recommend for or against the use of curcuma/curcuminoid for people with knee and/or hip OA,” the guidelines said.
Professor Bennell, Director of the Centre for Health, Exercise and Sports Medicine at the University of Melbourne, reiterated that there was just not enough evidence.
“There is not enough high quality, well powered studies to answer that. This [study] is probably in that basket.”
“This one was nicely conducted. They did it in a subgroup of patients who they thought might be more responsive. Most studies just take everybody with knee OA and we know knee OA is a heterogeneous disease so not everybody is the same.”
“They have chosen a group with an inflammatory presentation and hypothesised that if it is going to be effective it should be more effective in this group.”
“They were obviously powered to show the minimum clinically important difference for pain but they didn’t actually find that. So while it is statistically significant, the differences between the two groups in terms of how much they changed actually didn’t reach what we would call clinically relevant,” she said.
She said ongoing research was required including in different joints and combinations of therapies.
“I think there should be research to definitely state one way or the other because people spend a lot of money on them [supplements]. And if they really aren’t going to be beneficial it is kind of useful to know you are just wasting your money.”
“You are going to get better benefits by doing exercise. You are much better off with strengthening exercises and increasing physical activity for benefits such as pain reduction and other health benefits. And it will be cheaper.”