Background: Although substantial data have supported the effectiveness of acupuncture for treating knee osteoarthritis (OA), the number of points used has varied. The objective of this study was to compare the effectiveness of six and two acupuncture points in the treatment of knee OA.
Methods: A randomised trial of knee OA patients was conducted. Patients were randomly allocated into two groups of 35. The “six point group” received treatment at six acupuncture points, ST35, EX-LE4 (Neixiyan), ST36, SP9, SP10 and ST34, while the “two point group” received treatment at just the first pair of points, ST35 and EX-LE4. Both groups received twice weekly electroacupuncture on 10 occasions. Electrical stimulation was carried out at low-frequency of 3 Hz to all points, with the intensity as high as tolerable. Both groups were allowed to take a 200 mg celecoxib capsule per day for intolerable pain. Patients were assessed at baseline, week 5, week 9 and week 13, using a Thai language version of the Western Ontario and McMaster Osteoarthritis Index (WOMAC). Global assessment of change after 10 treatments was also recorded.
Results: Acupuncture at both six and two acupuncture points was associated with significant improvement. Mean total WOMAC score at weeks 5 and 13 of patients in both groups showed no significant difference statistically (p = 0.75 and p = 0.51). Moreover, the number of celecoxib capsules taken, global assessment of global change and body weight change of both groups also showed no statistical difference.
Conclusion: This evidence suggests that electroacupuncture to two local points may be sufficient to treat knee OA, but in view of some limitations to this study further research is necessary before this can be stated conclusively.
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An epidemiological study has shown that knee osteoarthritis (OA) affects about 35 percent of the Thai population aged over 60 years living in urban area of Bangkok.1 In general, the treatment of knee OA in Thailand has followed the guidelines of the American College of Rheumatology, classified into three groups: nonpharmacological modalities, pharmacological therapy and surgical treatment.2 One of the nonpharmacological modalities is acupuncture which was recommended as a level B treatment by the European League against Rheumatism in 2003.3 Moreover, several articles, research reports and systemic reviews have reported the effectiveness and safety of acupuncture for knee OA treatment.4–18 The number of knee OA patients mainly treated by acupuncture at Sirindhorn National Medical Rehabilitation Centre (SNMRC) has been increasing each year.
The number of acupuncture points used for treatment of knee OA has varied between studies. Using a greater number of points is likely to produce more discomfort, uses more needles and is more time consuming than using fewer points. Therefore, it would be valuable to know whether the use of fewer points is as effective as the use of a higher number of points. The lowest number of points that has been reported as effective is the two points per knee, ST35 and EX-LE4, used by Ng et al.19 Another study of 146 general knee pain patients, including knee OA, in China showed 96% total improvement rate from pricking at ST35 and EX-LE4 points.20 However, no study so far has compared the effectiveness of different numbers of acupuncture points for knee OA. This was the objective of the study reported here.
We conducted a randomised, comparative trial. The study protocol was approved by the ethics committee of SNMRC. We selected patients with symptomatic knee OA in the outpatient section of SNMRC according to the eligibility criteria summarised in box 1.
The sample size for testing the difference between means was calculated with the Epical 2000 programme, by setting the standard deviation of the Western Ontario and McMaster Osteoarthritis Index (WOMAC) score of 17.967 and mean difference of total WOMAC score between groups of 15, power of 0.9 and a level of significance at 0.05. A sample size of 30 patients per group plus an estimated 5 dropouts would be needed.
The patients were randomly allocated into two groups. Treatment allocation was carried out by block randomisation (block size two) using opaque sealed envelopes. We stratified by the main confounding factors, body mass index and baseline total WOMAC score, to ensure balance between groups.
The “six point group” received treatment at six acupuncture points: EX-LE4, ST35, ST36, SP9, SP10 and ST34.This choice of acupuncture point was based on the Traditional Chinese Medicine (TCM) theory for treating Bi syndrome, using local points on channels that traverse the area of pain.23 The “two point group” received treatment at only two of these points: EX-LE4 and ST35.
To avoid contamination, the two groups were scheduled to receive acupuncture treatment at different times. The depth of needling was 18–25 mm for EX-LE4 and ST35, 15–25 mm for SP9 and ST34 and 15–30 mm for ST36 and SP10. Both groups received acupuncture twice weekly from baseline to week 5, a total of 10 treatments. The skin was sterilised with 70% alcohol. Sterile disposable 30 gauge, 40 mm stainless steel acupuncture needles with guide tubes were used in all procedures. The needles were stimulated manually to elicit de qi, verified by the patients. Electrical stimulation was applied for 30 minutes with biphasic pulse continuous of 3 Hz, to the needles in the following pairs: EX-LE4 and ST35; ST36 and SP9; and SP10 and ST34. The stimulation intensity was as high as tolerable below the pain threshold, and was adjusted continuously according to the patient’s response. The acupuncture treatment was applied only to the knee that was painful.
Both groups were advised to do quadriceps exercise 30 times per day during the study period. Patients in both groups were allowed to take one 200 mg celecoxib capsule per day when intolerable pain occurred and the number of capsules taken was recorded by the patients.3 Both groups of patients were requested not to receive other treatments including any physical therapies, any pain-killing medicines and acupuncture treatment from another place.
Acupuncture treatment of both groups were carried out by the same medical doctor, a specialist in acupuncture accredited by the President of Shanghai University of Traditional Chinese Medicine, with more than nine years of clinical experience in acupuncture.
The modified Thai version of WOMAC osteoarthritis index for knee OA was used as the primary outcome, comprising numerical rating scales for the three dimensions, pain (0–50), stiffness (0–20) and physical function (0–150).24 The assessment was carried out by a well-trained nurse blinded to group allocation at 0, 5, 9 and 13 weeks. Secondary outcomes were the number of celecoxib capsules taken by the end of 13 weeks, and self assessment of global change after the acupuncture treatment, using a questionnaire with seven levels: much better, better, slightly better, no change, slightly worse, worse, worst.
Between-group analysis of WOMAC score was performed using an unpaired t test and the 95% confidence interval of the difference between groups. If WOMAC scores did not have normal frequency distribution, the data would be modified before testing; but if not normal after transformation, we used the nonparametric Wilcoxon Rank Sum test. To check whether the data had normal distribution frequency, we used Shapiro Wilk or W test. For the intention to treat analysis, the last available score was carried forward.
Recruitment took place between February and August 2007. From a total of 320 knee OA patients, 216 were excluded by exclusion criteria and 34 did not meet the inclusion criteria. The remaining 70 patients were included and randomly allocated into two groups of 35 patients, the two point group and the six point group.
During the first five weeks of acupuncture treatment, four patients dropped out of the study. Three were in the six point group: one for personal reasons; one because of back pain; one because of knee inflammation following over-activity after acupuncture. One patient in the two point group dropped out because of knee injury caused by a motorcycle accident. The WOMAC score at baseline was carried forward to all time points (weeks 5, 9 and 13), making the assumption of no change for non-completers. All patients receiving the full course of treatment attended for follow up at weeks 9 and 13.
Baseline characteristics of both groups are presented in table 1. Mean total WOMAC score at baseline of both groups showed no significant difference (p = 0.68). Reductions in mean total WOMAC score at weeks 5 and 13 compared to baseline were observed, and were highly significant (p<0.001 for all comparisons.) At both time points, there was no significant difference between the groups (p = 0.75 and p = 0.51) as shown in table 2. Also, there was no difference between group at 9 weeks, data not presented. Figure 2 shows that the mean total WOMAC score of both groups reduced sharply at the fifth week then remained fairly constant to the end of week 13.
Self assessment scores of change compared with before acupuncture were compared using exact test. No patients in either group chose slightly worse, worse or worst. There was no difference between the groups (p = 0.579) as shown in table 3. The number of celecoxib capsules used during the first five weeks and over the whole study period (13 weeks) of both groups showed no significant difference (p = 0.68 and p = 0.52) as shown in table 4. The body weight and the body weight change from baseline at week 5 and week 13 of both groups showed no significant difference (data not shown; p>0.05). Side effects were found in both groups. The total number of adverse events in 10 treatments in the six and two group were, respectively, contusion 11/8; dull pain 10/8; other 1/0. No patient withdrew because of any side effects.
In this study, the effectiveness of the two points and the six points acupuncture in knee OA, as assessed by the mean total WOMAC score at week 5 and week 13, showed no significant difference. We did not include a control group receiving no acupuncture treatment since several previous studies have already shown the effectiveness of acupuncture in the treatment of knee OA.7–16
According to our literature review on acupuncture for knee OA, there were several studies using four points,16 six points,11 nine points,7810 and more than nine points per knee.9 Based on this review, we selected six frequently used points, all of which are indicated for treatment of knee pain because they are placed on channels that traverse the knee joints. Among the six points, ST35 and EX-LE4 were the only two points located directly at the knee joint, the other four points being relatively distant.
In one reference textbook,25 ST35 is described as a common point for treating pain of the knee joints, and EX-LE4 is used for treating of both knee pain and knee arthritis. Moreover, ST35 is common to several clinical trials as a major point for treating knee-related disorder.8141626 Berman et al performed nine point acupuncture for treating knee OA, but applied electrical stimulation only at EX-LE4 as it was regarded theoretically as the most important point.8 This evidence all suggests that ST35 and EX-LE4 are the two major points for treatment of knee OA. We regarded the other points we used as supporting points.
One limitation of the study is that it was powered to show a difference between groups, and not for equivalence. To show that two and six point treatments were truly equivalent, we would probably require a much larger number of patients. However, the confidence intervals for the two groups in fig 2 overlap to a considerable extent, suggesting that any difference between the treatments is small and possibly not clinically significant.
Another potential limitation is that the effect of home exercises may have concealed any effect of acupuncture. However, from the results of a recent systematic review, we do not believe it likely that quadriceps exercises alone would have produced a fall as great as 70 points in the WOMAC score over eight weeks.27
We must consider whether the effect can be explained by differential usage of analgesic drugs. There was a trend towards greater use of drugs in the two point group, whose mean number of the capsules at week 13 was greater (6.0 capsules) than in the six point group (4.5 capsules). However, the difference was not statistically significant, and the total number of capsules used over the 13 week period was very low. Therefore, it is unlikely that the difference was due to the greater use of pain medication in the two point group. Moreover, since the usage of analgesics was relatively low, it seems unlikely to have been sufficient to have concealed any difference in the effects of the two acupuncture regimens.
It is generally accepted that acupuncture can reduce pain via at least two mechanisms7: (1) activation of the gate control system28; (2) stimulation of neurochemical release in the central nervous system.29–31 In addition, it has been reported that using low frequency (2–6 Hz) electrical stimulation can induce endorphin release.31 Since we found no statistically significant difference between our groups, we suggest that the effect of electroacupuncture (EA) at these ST35 and EX-LE4 alone, given twice weekly for 10 treatments, was likely to be an “adequate” treatment, at least for our patients in this particular setting, so that additional treatment to other points added nothing to the effect. It should be noted that these findings may not apply to acupuncture for chronic knee pain from other conditions, or pain as part of a general systemic condition.
In one review of 13 randomised, controlled trials for knee OA, Vas and White speculated that the optimal result from acupuncture treatment may involve: high temperature climate, high expectation of patients; minimum of four needles; EA rather than manual acupuncture; strong electrical stimulation; and a course of at least 10 treatments.15 Our study was performed in Thailand where the climate is tropical, and we used EA with strong electrical stimulation for 10 treatments. However, we have found that two needles per knee are adequate for treatment to be effective.
A study in knee OA comparing treatment in three groups (n = 8) receiving EA at ST35 and EX-LE4, transcutaneous electrical nerve stimulation (TENS) and a control group receiving only knee care education concluded that both EA and TENS treatment were effective in reducing knee pain, and EA treatment gave better improvement in function than TENS.19 Our study using the same two points EA showed the effectiveness in knee OA treatment.
Previous studies have observed that the effectiveness of acupuncture treatment in knee OA lasted for at least one month after the end of treatment.89 In our study, the mean total WOMAC score of both groups reduced greatly at week 5 after 10 treatments, as compared to baseline, and remained fairly constant at that low level for at least eight weeks (fig 2). This carry-over effect has also been reported in treatment by diacerein, one of the symptomatic slow acting drugs for OA (sysadoa).32 However, we could not absolutely be certain that this was solely due to the effect of acupuncture or partly because of the quadriceps exercise that the patients of both groups did for 30 times per day.
We found no difference between the effectiveness of EA in treating knee OA using two points at ST35 and EX-LE4 alone, and six points, viz ST35 and EX-LE4 together with ST36, SP9, SP10 and ST34. Although there are possible limitations, the results suggest that EA given to two local points on the knee, twice weekly for 10 weeks, could be an adequate treatment for this type of condition. Since this question relates to the efficiency of acupuncture practice, further research to address it is recommended. The point EX-LE4 lies directly over the joint space of the knee and therefore should be used with great caution to avoid the risk of joint space infection.
Box 1 Eligibility criteria
Clinical criteria for the classification of knee OA followed American College of Rheumatology using classification tree including21:
1.1 Knee pain and age ⩾40 years and
1.2 Morning stiffness ⩽30 minutes in duration and
1.3 Crepitus on motion
Documented radiographic change of OA (Kellgren-Lawrence,22 grade ⩾2)
Patients agree to sign consent form.
History of bleeding disorder or currently use of anticoagulants
Knee inflammation or knee contracture
3. History of knee surgery
Intra-articular corticosteroid or hyaluronate injection in the knee during the past six months
Pregnancy or breast feeding
Previous experience with acupuncture due to knee OA during the past 12 months
Previous attending physical therapy program or other treatment for knee OA (with the exception of nonsteroidal anti-inflammatory drugs) during the past four weeks
Serious uncontrolled concomitant illness (eg, coronary artery diseases)
Diseases causing referred pain to the knee, eg, Myofascial pain syndrome (MPS), disc herniation
Currently receiving antineoplastic or immunosuppressive drugs.
Unable to do activity of daily living and unable to follow the program
Obesity with body mass index ⩾32 kg/m2
Contraindication to medication with celecoxib
History of severe gastric-duodenal ulcer.
History of taking chondroprotective agents, eg, glucosamine sulphate.
Trials have shown that acupuncture is an effective treatment for knee osteoarthritis
However, it is not known what id the optimal number of points to treat
In this RCT, we found no difference between electroacupuncture given at two compared with six points
We thank Attasit Srisubat, Cheng Zicheng, Manat Pongchaidecha, Prapun Phongkhanittanon, Punnee Pitisuttithum, Sanguansak Thanaviratananich, Somkiat Potisat, Sompon Thassaniyom, Somkiat Asawapooreekorn and Vilai Kuptniratsaikul.
Funding: This study was granted by the Academic Supporting Fund of Medical Services Department.
Competing interests: None.
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