Outpatients aged 60 years or older with knee OA were recruited from the Meiji University of Oriental Medicine Hospital. The patients had been clinically and radiologically diagnosed of knee OA according to the criteria of the American College of Rheumatology. Further inclusion criteria for the present study were: (1) knee pain lasting for six months or longer; (2) no radiation of knee pain; (3) radiographic evidence of at least one osteophyte at the tibiofemoral joint (Kellgren-Lawrence grade ≥ 2); (4) normal neurological functions of lumbosacral nerve, including deep tendon reflexes, voluntary muscle action and sensory function; and (5) not receiving acupuncture treatment for more than six months. Exclusion criteria were: (1) major trauma or systemic disease; and (2) receiving conflicting or ongoing co-interventions. Patients under drug treatment were included if there had been no change in medicine and its dosage for one month or longer. This study was approved by the Ethics Committee of the Meiji University of Oriental Medicine.
All enrolled patients gave their written informed consent. According to a block randomised allocation table (generated by Sample Size, version 2.0, Int), the enrolled patients were allocated to (1) the control (CT) group, (2) the acupuncture (ACP) group, (3) the transcutaneous electrical nerve stimulation (TENS) group or (4) the acupuncture and TENS (A&T) group.
The design of this study was a randomly controlled clinical trial using a block randomised procedure. Each patient received a total of five treatments, once per week, and follow-up was measured for ten weeks after the first treatment.
Control (CT) group
The CT group patients did not receive any specific treatment, but when necessary, were allowed to use topical poultice containing methylsalicylic acid.
Acupuncture (ACP) group
The ACP group patients received acupuncture treatment at selected acupoints for 15 minutes on the OA affected knee. The selected acupoints are widely accepted for treating knee pain [6–13], namely Liangqiu (ST34), Dubi (ST35), Zusanli (ST36), Yinlingquan (SP9), Xuehai (SP10) and Yanglingquan (GB34). Disposable stainless steel needles (0.2 mm × 40 mm, Seirin Co Ltd) were inserted into the muscle to a depth of 10 mm using the 'sparrow pecking' acupuncture technique (alternate pushing and pulling of the needle) by acupuncturists who had four years of acupuncture training and three to eight years of clinical experience. When the subject felt dull pain or the acupuncture sensation (de qi) was achieved, the needle manipulation was stopped and the needle was left in place for ten more minutes.
Transcutaneous electrical nerve stimulation (TENS) group
The TENS group patients received treatment at the OA affected knee for 15 minutes from a single-channel portable TENS unit (model HV-F3000, OMRON Healthcare Co Ltd, Japan), which sends between two electrodes a premixed amplitude-modulated frequency of 122 Hz (beat frequency) generated by two medium frequency sinusoidal waves of 4.0 and 4.122 kHz (feed frequency). Surface disposable electrodes of 809 mm2 and 5688 mm2 were respectively placed on the site with the most tenderness and the opposite side of the site. Two electrodes were different in size (ratio: 1:7). The smaller one was placed on the site of tenderness. The intensity of TENS stimulation was adjusted so that a tingling sensation 2–3 times of the subject's sensory threshold was produced.
Acupuncture and transcutaneous electrical nerve stimulation (A&T) group
The treatment for the A&T group combined the treatments for the ACP and TENS groups. The patients received 15 minutes of TENS, and then 15 minutes of acupuncture treatment at the OA affected knee.
We confirmed that the patients in all groups did not receive any other co-interventions including analgesics, anti-inflammatory agents or topical hyaluronic acid injection during the study period.
Primary outcome measures were: (1) pain intensity, quantified with a 10 cm visual analogue scale (VAS, 0 – 100 mm) and (2) pain disability measured with the Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC, 0 – 100 points) . The WOMAC consists of 24 questions each with five possible responses.
The VAS scores were measured immediately before the first treatment and subsequently at one, two, three, four, five and ten weeks after the first treatment. The WOMAC scores were measured immediately before the first treatment and subsequently five and ten weeks after the first treatment. Each VAS and WOMAC score was measured immediately before treatment of the specified week.
Repeated measures analysis of variance (ANOVA) was used to study the changes in the VAS and WOMAC scores in the three groups. Changes in the time course among groups were considered significant when the interaction was significant at a level of 0.013 (0.05/4). After detection of significant changes in the overall time course with repeated measures ANOVA, pair comparisons were detected with Bonferroni correction. StatView for Windows (version 5.0) or SYSTAT 10 (SYSTAT Inc) was used for the statistical analysis. The results with P values of less than 0.05 were considered statistically significant.