Reviewed: Kuptniratsaikul V, Thanakhumtorn S, Chinswangwatanakul P, Wattanamongkonsil L, Thamlikitkul V. Efficacy and safety of Curcuma domestica extracts in patients with knee osteoarthritis. J Altern Complement Med. 2009;15(8):891-897.

Osteoarthritis (OA), a degenerative joint disorder, is a common cause of disability for both men and women. Nonsteroidal antiinflammatory drugs (NSAIDs) are the most common form of treatment for relieving pain associated with OA, but they can cause serious adverse side effects that impact gastrointestinal, renal, and cardiac health. Curcumin present in turmeric (Curcuma longa, syn. C. domestica, Zingiberaceae) extracts has been reported to have anti-inflammatory and antioxidant properties. Researchers from Mahidol University in Bangkok, Thailand conducted a study to determine the efficacy and safety of a turmeric extract in reducing pain and improving function in patients with knee OA.

Conducted at Siriraj Hospital in Bangkok, from April 2005 to May 2006, the study included adult subjects who had primary knee OA according to the American Rheumatism Association criteria. To be included in the study, patients had to have knee pain and radiographic osteophytes, as well as at least 1 of the following characteristics: being older than 50 years of age, suffering from morning joint stiffness lasting less than 30 minutes, and/or experiencing crepitus (crackling in joints) on motion. Patients reporting a pain score of ≥ 5 of 10 in a numerical rating scale were recruited.

The patients were asked to discontinue their medications for knee OA 1 week before randomization. All patients were randomly allocated to receive either ibuprofen (400 mg twice daily) or turmeric extract (500 mg curcuminoids 4 times daily) for 6 weeks.

According to the authors, the turmeric extracts were produced by the Thai Government Pharmaceutical Organization under the Good Manufacturing Practices standard. Dried turmeric rhizomes were ground into powder. The turmeric powder was extracted with ethanol and then evaporated at low pressure to obtain ethanolic extracts containing oil and curcuminoids. The oil was then removed. Each capsule of extract contained 250 mg curcuminoids.

The patients were assessed every 2 weeks. The main outcomes were pain on level walking and pain on stair climbing, measured by a numerical rating scale, as well as knee functions assessed by the time spent on a 100-meter walk and going up and down 10 steps.

All patients had blood tests assessing complete blood count, liver function, and renal function at week 0 and week 6. At week 6, the patients’ satisfaction with treatment was evaluated by a 5-category scale (high, moderate, little, same, or dissatisfaction).

Of 190 patients screened, 107 were selected for the study; 52 were randomly assigned to the curcuminoid group and 55 to the ibuprofen group. Of those, 45 patients in the curcuminoid group and 46 patients in the ibuprofen group completed the study. Most of the patients were overweight (average body mass index greater than 25) elderly women. The duration of symptoms before entering the trial was approximately 20 months. Half of the patients had bilateral knee OA. At baseline, the mean pain scores on level walking and on the stairs, as well as the time spent on the 100-meter walk and on the flight of stairs, were similar between the 2 groups.

The authors report that the mean scores of all outcomes in both groups at week 6 were significantly improved when compared with the baseline values. For example, from week 0 to week 6, the scores for pain on level walking dropped from 5.3 ± 2.3 to 2.7 ± 2.5 for the curcumin group and from 5.0 ± 1.9 to 3.1 ± 2.3 in the ibuprofen group. There was no significant difference in those parameters between the 2 groups, except that pain on stair climbing was less for those taking curcuminoids (P = 0.016). Also, the curcuminoid group seemed to spend less time on the 100-meter walk and going up and down a flight of stairs. No significant differences were found for adverse events between the 2 groups, with dyspepsia (stomach upset; curcuminoids 20.8%, ibuprofen 26.9%) most common. Interestingly, many patients in the curcuminoid extract group who experienced bloating symptoms and passing gas described these symptoms as beneficial gastrointestinal effects, whereas those in the ibuprofen group reported gastrointestinal irritation symptoms.

Regarding satisfaction, most patients rated themselves as having moderate to high satisfaction (91.1% in the curcuminoid group, 80.4% in the ibuprofen group). The patients’ satisfaction with treatment was not statistically significantly different (P = 0.15) between the groups. The patients in the ibuprofen group had better compliance to the treatment regimen than those in the curcuminoid extract group (90.1% versus 82.8%, P = 0.001). This finding was attributed by the researchers to the fact that ibuprofen was given twice a day, whereas curcuminoid extract had to be taken 4 times a day.

These results suggest that curcuminoid extracts of turmeric might be as effective as ibuprofen in alleviating knee pain and improving knee functions, with a trend toward a greater effect in patients receiving curcumin extracts. However, the wide range of 95% confidence interval (CI) indicated that the study had an inadequate sample size; the proper sample size should be 70 patients per groupThe authors recommend more studies with an adequate sample, a higher dose of ibuprofen in the comparison group, and a double-blind technique to demonstrate the efficacy of turmeric extracts in alleviating knee pain and improving knee function.

—Shari Henson