Objective To compare the immediate effects of electroacupuncture and manual acupuncture on pain, mobility and muscle strength in patients with knee osteoarthritis.
Methods Sixty patients with knee osteoarthritis, with a pain intensity of ≥2 on the pain Numerical Rating Scale, were included. The patients were randomised into two groups: manual acupuncture and electroacupuncture. Pain intensity, degree of dysfunction (Timed Up and Go (TUG) test), maximal voluntary isometric contraction and pressure pain threshold were assessed before and after a single session of manual acupuncture or electroacupuncture treatments.
Results Both groups showed a significant reduction in pain intensity (p<0.001) and time to run the TUG test after the acupuncture treatment (p=0.005 for the manual acupuncture group and p=0.002 for the electroacupuncture group). There were no differences between the groups regarding pain intensity (p=0.25), TUG test (p=0.70), maximum voluntary isometric contraction (p=0.43) or pressure pain threshold (p=0.27).
Conclusions This study found no difference between the immediate effects of a single session of manual acupuncture and electroacupuncture on pain, muscle strength and mobility in patients with knee osteoarthritis.
Trial Registration Number: RBR-9TCN2X.
- Pain Management
- Pain Research
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Osteoarthritis (OA) is the most prevalent joint condition and is characterised by progressive erosion of the articular cartilage. Clinically, patients have pain due to compressive overload or excessive physical activity which eases with rest but, in the late stages, patients have pain even during rest. There is also a loss of function, with limited movement and difficulty in performing daily activities.1
The annual cost of treatment of patients with OA with non-steroidal anti-inflammatory drugs in the UK is £19.2 million.2 The direct healthcare costs of patients with OA are more than twice those of similar patients without the condition in the USA.3 OA of the knee is the most common type.1 Treatment is focused on symptoms using pharmacological and non-pharmacological therapies such as anti-inflammatory drugs,4 occupational therapy,5 exercise programmes6 and acupuncture.7
Acupuncture is an important component of traditional Chinese medicine and has been used as an effective form of pain treatment.8–10 According to Western medicine, acupuncture relieves pain through the gate control mechanism involving the release of neurotransmitters and endogenous opioids.11 When stimulated, muscle afferent fibres convey impulses to the spinal cord, releasing endorphins and monoamines and stimulating pain inhibition. Recent studies have reported the release of cortisol as an anti-inflammatory action that also contributes to reducing pain.12–15
Electroacupuncture (EA) is a technique in which two needles are inserted into the body of the patient, acting as electrodes, allowing the passage of an electrical current. At least one of the needles is inserted into an acupuncture point. Although EA is becoming more popular, manual acupuncture (MA) is still the most commonly used technique. MA consists of inserting thin needles into acupuncture points, followed by manipulation such as twisting or lifting and pushing the needle.16 ,17 One of the main advantages of using EA in clinical practice or research is the ability to objectively and quantifiably set the stimulation frequency and the intensity of the current.18 Low-frequency EA (2 Hz) induces the release of enkephalins, β-endorphins and endorphins that activate the µ- and δ-opioid receptors. High-frequency EA (100 Hz) induces the release of dynorphins, which activate κ-opioid receptors.19 ,20 Clinical studies suggest that EA is effective for treating many types of pain.19–21
To date, only a few studies have compared the two forms of stimulation10 ,16 and there are no studies comparing MA and EA in patients with knee OA. The present study aimed to compare the immediate effects of EA and MA on pain, mobility and muscle strength in patients with knee OA after a single session.
A two-arm randomised controlled study with a blind examiner was conducted at the Physical Therapy Clinic of the Universidade Cidade de São Paulo (UNICID). This study was part of a Master’s Degree thesis for RP. Data collection started in April 2012 and ended in June 2012.
Inclusion and exclusion criteria
Patients of both genders aged 40–80 years referred for physical therapy treatment at the UNICID clinic with knee pain intensity ≥2 on the pain Numerical Rating Scale (NRS)22 and radiographic examinations showing knee OA grades II, III or IV according to the classification of Kelgren and Lawrence23 ,24 were eligible for the study.24 All patients had knee OA according to American College of Rheumatology criteria.25 The exclusion criteria were the inability to walk, a history of cancer, neurological deficits (sensory or motor), cardiac pacemaker, metal prostheses, type I diabetes, uncontrolled systemic arterial hypertension, morbid obesity or the use of antidepressants, tranquillisers or anti-inflammatory steroids in the last 3 months; patients who were undergoing physical therapy sessions and using analgesics on the day of the treatment were also excluded.
Procedures, random allocation, physical assessments and interventions
Demographic data, pain intensity (measured by the pain NRS), degree of dysfunction (by the Timed Up and Go (TUG) test), muscle strength (measured by an isokinetic dynamometer) and pressure pain threshold (PPT, measured using a pressure algometer) were obtained. The knee that exhibited the greatest pain intensity was evaluated in patients with bilateral pain.26
After evaluation and enrollment, an opaque envelope was opened to reveal the intervention consisting of a single session of either MA or EA. The permuted block randomisation using sequentially numbered and sealed opaque envelopes27 was conducted by a researcher who was not involved in the data collection.27 ,28
Needles of 0.25 mm in diameter and 30 mm in length (Zhongyan Taihe Medical Instruments, Beijing, China) were used in this study for both MA and EA treatments and were inserted to a depth of 0.5 cm. All patients were treated lying in a supine position on a couch. EA treatment consisted of placing the acupuncture needles at specific treatment points and an electrical stimulator was then connected to the needles with alligator clips. The stimulus intensity was increased until the patient reported a strong but comfortable intensity. A Sikuro DS100C electrical stimulator with the following parameters was used: signal three with two frequencies, 3 Hz (with pulse duration of 1 ms) and 100 Hz (with pulse duration of 0.88 ms), both with a 3 s duration for 30 min.18 For treatment with MA, the acupuncture needles were placed at the same specific treatment points and then the manipulation technique was used every 3 min for a total of 30 min. The points used in both the treatments were LI4 Hegu and LR3 Taichong bilaterally, and ST36 Zusanli, ST35 Dubai, Xiyan and SP10 Xuehai on the most painful side.29
The patients were reassessed after the treatment by the examiner, who was blind to the group allocation, using the same instruments as those used in the pretreatment assessment.
Measuring instruments and outcomes
Pain NRS was used to evaluate the pain intensity. This scale has 11 points, with 0 representing ‘no pain’ and 10 representing ‘as bad as one can imagine’.
The TUG test measures the time it takes for an individual to get up from an armchair without using their arms after the examiner gives the verbal command ‘GO’, walk 3 m at normal speed, turn around, walk back and sit down again on the chair. The patients wore their usual shoes, and supports such as canes were not used to help them to walk. The test was performed once for familiarisation and a second time for measurement.30–32
Isokinetic dynamometry involved the patients sitting on the chair of the Cybex Norm-6000 isokinetic dynamometer with the knee to be evaluated positioned at a 60° angle. The patients performed three maximum voluntary isometric contractions (MVIC) and the peak torque was then recorded.22 ,33
PPT was measured using a pressure algometer (Somedic AB, Sweden). The participants remained lying on a stretcher, and eight points were marked on the painful knee. The first point was located 2 cm below the medial border of the patella; the second was 2 cm below the lateral border of the patella; the third was 3 cm laterally to the middle of the lateral border of the patella; the fourth was 2 cm above the lateral border of the patella; the fifth was 2 cm above the highest point of the upper border of the patella; the sixth was 2 cm above the medial border of the patella; the seventh was 3 cm laterally to the middle of the medial border of the patella; and the eighth was in the centre of the patella.34 During PPT measurement the circular probe of the algometer (with 1 cm2 area) was placed perpendicular to the skin and pressed at a rate of approximately 30 kPa/s.35 The participants were asked to press a button when the pressure became a clear sensation of pain. Three measurements (in kPa) were collected from each area in three series,36 always progressing from site 1 to site 8. The mean of the three measurements was used for data analysis. Subsequently, the mean of the eight means of the analysed points was calculated. An increase in PPT values after treatment represents a hypoalgesic response while a decrease in PPT represents a hyperalgesic response.
A preliminary study of intra-examiner reliability in the measurement of the PPT36 was performed by the examiner in the present study using the points described before.30 Ten patients with knee OA were selected and were evaluated on two different occasions with a 48 h interval between them. Three measurements (in kPa) were taken from each recording site at each time point and the average used for data analyses. The reliability was considered to be excellent with an intraclass correlation coefficient of 0.97.
The primary outcome measure was pain intensity (pain NRS 0–10). Sample size calculation was performed a priori considering a 2.0 point difference for the intensity outcome and an estimated SD of 2.5 points29; 80% statistical power, α=5% and a possible sample loss of 15% were considered. Thus, 30 patients were needed per group (60 in total).
Using descriptive statistics, the data on variables were presented as mean and SD. The values of pain intensity (NRS), time in seconds for the patient to walk 6 m (TUG), PPT and muscle strength (MVIC) observed after the treatment were compared between the groups using a two-way factorial mixed ANOVA with repeated measures considering the time (pre- and post-treatment) as a within-subject effect and the group (MA and EA) as a between-subject effect. The effect of each treatment was verified by differences in the within-subject comparison (based on the differences between the pre- and post-treatment means) within each group. Data normality was verified using the Kolmogorov–Smirnov test. The data were analysed using SPSS software V.15.0 for Windows. All tests were performed assuming a significance level of α=5%.
The patients were selected in January 2012. The characteristics of the patients are described in table 1. The participants were mostly women with a mean age of 63 years. The values of the demographic variables were similar in both the studied groups. A total of 85 patients were screened for eligibility, of whom 30 were randomly assigned to the MA group and 30 to the EA group; none were excluded from the analysis. A detailed flowchart of the processes of recruiting, exclusion, evaluation and intervention is shown in figure 1.
Table 2 shows the pre- and post-treatment values of pain intensity, TUG results, isokinetic dynamometry and PPT of both the groups, represented as mean (SD) and p value. There was no difference between the two treatments for the pain intensity outcomes (p=0.25), TUG test (p=0.70), MVIC (p=0.43) or PPT (p=0.27). Both the groups showed significant reductions in pain intensity (p<0.001) and the execution time of the TUG test (p=0.005 for the MA group and p=0.002 for the EA group). There were no significant differences between the other outcomes in the within-group analyses.
This study aimed to test the immediate effects of a single session of MA or EA in patients with knee OA. There was a significant reduction in pain intensity and in the execution time of the TUG test in both of the groups. However, there was no significant increase in the muscle strength or the PPT. In addition, there was no significant difference between the groups for all the outcomes evaluated.
The reduction in the pain intensity after one session of MA can be explained by the release of neurotransmitters such as endorphins and monoamines (serotonin and noradrenaline) which block pain messages.12 ,13 ,37 The improvement resulting from EA can be explained by the release of the same substances that are released in MA, in addition to the release of enkephalins, β-endorphins and endorphins which activate the µ and δ-opioids and of dynorphins which activate the κ-opioid receptors,19 ,31 which could potentiate the effects of the treatment. However, in the present study no additional effects were observed with the use of EA compared with MA.
Acupuncture has been proved to be effective for the treatment of several types of chronic pain and has a better performance than a placebo intervention.21 In a study comparing acupuncture and pharmacological treatment, placebo acupuncture and pharmacological treatment and pharmacological treatment alone in patients with knee OA there was a reduction of 2.78, 1.58 and 1.34, respectively, in the mean pain intensity after 4 weeks of treatment.7 Ahsin et al12 studied patients with knee OA and demonstrated that the EA group showed a greater reduction (72% on average) in mean pain intensity than the placebo group, which did not show any reduction. In the present study the pain was reduced by 2.04 points in the MA group and by 2.66 points in the EA group, which suggests that this reduction results from the placebo effect and also from a real effect of the treatment.
The improved TUG execution time corroborates other studies that found improved mobility in patients with knee OA after EA.32 A recent study on transcutaneous electrical nerve stimulation (TENS) in patients with knee OA showed a decreased TUG execution time of 0.52 s in the placebo TENS group38 while, in the present study, the difference was 1.29 s in the MA group and 1.08 s in the EA group. Again, these data suggest that the reduction in the TUG execution time was not only due to the placebo effect, but the learning effect cannot be discarded.
There was no significant effect on muscle strength after the MA or EA sessions. There are reports in the literature of increased muscle strength after MA, demonstrated only in another muscle group, the biceps brachii.34 The status of the weakness of the quadriceps muscle as a risk factor in patients with knee OA is still controversial,39 although a relationship is often found in this population.40
In the present study the EA group showed a slight trend towards greater treatment effectiveness based on the increase in the PPT, which was not significant. Some studies suggest that PPT assessment must be performed in patients with knee OA because it allows evaluation of the local and generalised sensitisation.35 High- and low-frequency TENS increased PPT in patients with knee OA after a single treatment session.38 The difference between the characteristics of the therapeutic modalities (TENS vs MA or EA) may be responsible for the discrepancy in the observed results.
The study has some limitations. The major limitation refers to the realisation of a single session of MA and EA, and only the immediate effect of the two treatment techniques was evaluated. Further studies are needed to assess the effects of cumulative MA or EA treatment sessions with longer follow-up times. Additionally, due to the nature of the interventions, it was not possible to blind the therapist.
There is no significant difference between the immediate effects of a single session of MA and EA on pain, muscle strength and mobility in patients with knee OA.
Manual acupuncture and electroacupuncture are both used to treat osteoarthritis pain but are rarely compared directly.
As a first step, we compared the effect of a single session of each.
Pain was reduced by 42% and 52% following manual acupuncture and electroacupuncture, respectively, with no significant difference between the groups.
Contributors RP, REL: conception and design of the study and writing the manuscript. RP, WBV, FADA: data acquisition. EYN: data analysis.
Competing interests None.
Patient consent Obtained.
Ethics approval Ethics approval was obtained from the Ethics Committee of Universidade Cidade de Sao Paulo (UNICID).
Provenance and peer review Not commissioned; externally peer reviewed.
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