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Year : 2014  |  Volume : 2  |  Issue : 2  |  Page : 69-74

Effects of conventional and acupuncture-like transcutaneous electrical nerve stimulation on osteoarthritis of the knee

Department of Medical Rehabilitation, University of Maiduguri, Maiduguri, Borno State, Nigeria

Date of Web Publication17-Nov-2014

Correspondence Address:
O G Sokunbi
Department of Medical Rehabilitation, University of Maiduguri, Maiduguri, Borno State
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2348-0149.144835

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Background: Transcutaneous electrical nerve stimulation (TENS) is one of the most widely used physical modalities for the management of osteoarthritis (OA) knee and various stimulation parameters have been adopted with varying stimulation frequencies. However, the optimal stimulation frequency of TENS in the management of OA knee pain appeared not to have been well studied. Aim: The purpose of this study is to find out, which among conventional TENS (ConTENS) and acupuncture-like TENS (AcuTENS) is more effective for treating knee OA. Materials and Methods: Twenty-four patients with knee OA were randomly allocated to three groups. ConTENS AcuTENS and Placebo TENS (PlaTENS). Participants in the ConTENS and AcuTENS group received TENS treatment with current intensity and frequency based on their group allocation at selected acupuncture points (acupoints) for knee pain; the Pla-TENS participants received intervention, which was identical to the ConTENS treatment group, but the circuit was disconnected. Participants in the three groups were also treated with soft tissue manipulation around the knee joint. Each group received treatment 3 times a week for 3 weeks during the study. Outcome measures were pain intensity measured with numeric pain rating scale (NPRS), goniometric assessment of knee active range of motion and knee functional mobility measured with timed up and go test. Data were collected prior to intervention, at weekly basis during intervention and at 4 weeks follow-up assessment. Results: The ConTENS and AcuTENS reported lower pain intensity scores and increase in the knee active range of flexion than the PlaTENS group at the end of 3 weeks of treatment and at follow-up assessments. However, only the AcuTENS group recorded statistically significant lower pain intensity and improvement in knee flexion than other groups (P < 0.005). Conclusion: AcuTENS treatment was more effective than ConTENS in pain relief and increasing active range of knee flexion for patients with OA of the knee

Keywords: Acupuncture, knee joint, osteoarthritis, transcutaneous electrical nerve stimulation

How to cite this article:
Sokunbi O G, Usman M B. Effects of conventional and acupuncture-like transcutaneous electrical nerve stimulation on osteoarthritis of the knee. Niger J Exp Clin Biosci 2014;2:69-74

How to cite this URL:
Sokunbi O G, Usman M B. Effects of conventional and acupuncture-like transcutaneous electrical nerve stimulation on osteoarthritis of the knee. Niger J Exp Clin Biosci [serial online] 2014 [cited 2023 Mar 26];2:69-74. Available from: https://www.njecbonline.org/text.asp?2014/2/2/69/144835

  Introduction Top

Osteoarthritis (OA) is the most common form of arthritis [1] affecting 80% of those aged 65 or older. [2] It is the eighth leading cause of disability globally, [3],[4] with the knee joint most frequently associated with disability. OA of the knee causes patients severe discomfort and a reduced ability to work. [1],[2] Knee OA is responsible for a higher percentage of disability than any other medical condition for the following activities: stair climbing, walking a mile and housekeeping. [5] Anti-inflammatory drugs used to treat the symptoms of this disorder, usually, have various side-effects. [3] Patients with chronic pain increasingly seek alternative methods for pain relief, particularly transcutaneous electrical nerve stimulation (TENS).

Transcutaneous electrical nerve stimulation is one of the most widely used physical modalities for the management of OA knee. [5] TENS has the advantage of being efficacious, inexpensive, simple and essentially free of side effects. TENS may even be used at home by patients themselves due to its portability and simplicity. Acupuncture is a system of healthcare, which has been practiced for more than 3000 years. [6] Classical acupuncture is based on the theory that vital energy, called de qi, flows through the body along pathways called meridians. There are specific points along these meridians, called acupuncture points, or acupoints, at which the de qi may be accessed. Inserting needles into these points permits the practitioner to restore harmony to the system by rebalancing the flow of de qi.[7] In the Western medical model, acupuncture is thought to relieve pain through the gate-control mechanism or through the release of neurochemicals. [8],[9],[10] Stux and Pomeranz [11] describe the possible neural mechanisms of acupuncture analgesia as follows: Small diameter muscle afferents are stimulated, sending impulses to the spinal cord, which then activates three centers (spinal cord, midbrain, and pituitary) to release neurochemicals (endorphins and monoamines) that block pain messages. It seems that the practice of acupuncture has not gained so much popularity and acceptance when compared with the use of TENS in Nigeria where this present study was carried out.

Research into TENS for OA knee pain has been carried out for more than 20 years, and various stimulation parameters have been adopted with stimulation frequencies ranging from 2 Hz to 100 Hz. Jensen et al. [12] reported the effectiveness of conventional TENS (ConTENS) (80 Hz, 150 s) in relieving pain due to OA of the knee. Han et al. [13] found that using low-frequency (2 Hz pulse trains), high intensity also known as acupuncture-like TENS (AcuTENS) mode on patients with chronic pain increased the cerebrospinal fluid levels of endorphins. Subsequent to their findings, several studies examined the efficacy of acupuncture and TENS treatment for chronic pain conditions; however, there results were inconclusive. [5],[6],[7],[8] The present study was carried out to investigate the effects of ConTENS and AcuTENS on knee OA among Nigerian adults.

  Materials and methods Top


A randomized placebo-controlled trial.

Ethical approval

Approval for the study was sought and obtained from the Hospital Research and Ethics Committee of University of Maiduguri Teaching Hospital (UMTH), Maiduguri, Borno State, Nigeria before commencement of the study. After explaining the experimental procedures and the potential risks involved, a written informed consent was obtained from all the participants.


The participants for this study were males and females aged 45 years and above who have been clinically and radiologically diagnosed with OA of the knee Joint according to American College of Rheumatology. They are patients who are attending Physiotherapy Clinics of UMTH, Maiduguri, Nigeria. Further inclusion criteria include knee pain lasting for 3 months or longer with no other medical and surgical conditions such as benign or malignant tumors. Patients currently on analgesics at the time of the study were allowed to participate only if the medications had made no changes to their symptoms and there had been no changes in the dosage for at least 1 month prior to the commencement of this study. Patients with skin conditions that might impair skin sensation or prevent the use of TENS on the knee joints were also excluded.

Sample size estimation

Sample size estimation was based on the assumption that TENS could reduce pain intensity by at least 1.5 on numeric pain rating scale (NPRS) (this was based on the previous work by Itoh et al. which explored the effect of acupuncture and TENS in the treatment of knee OA). To yield a power of 80% with a significant level of 0.05, a sample size of at least 6 subjects in each group was required (sample size estimation was determined by power analysis sample size software).


Participants were randomized into three groups using a computer generated table of randomization; ConTENS group, AcuTENS group and Placebo TENS (PlabTENS) group.


Assessments of pain intensity, active range of knee movements and functional mobility were carried out prior to intervention, and at 1 st week, 2 nd week, and 3 rd week of intervention and at 4 weeks post-intervention follow up assessments. Pain intensity was measured with (NPRS. NPRS is a verbally administered scale that measures pain intensity (0 = ''no pain at all'' to 10 = ''worst possible pain). Reliability and construct validity of NPRS with visual analog scale was reported by von Baeyer et al. [14] Knee joint active range of motion was measured with Universal goniometer according to the procedure stated by Watkins et al. [15] with the participants in supine lying position. Universal goniometer was found to have greater validity when measuring the large angles of knee flexion (r = 0.73 and 0.77). [15] Functional mobility was assessed with timed-up-and-go test. With participants seated in chair with knee and hip joints maintained at 90°, feet in contact with the floor and with the forearm resting on the arm rest, the timed-up-and-go test was carried out as described by Nordin et al. [16] The timed-up-and-go test has been validated and showed good intrarater and interrater reliability (r = 0.93 and 0.96, respectively). [16]


Dual-channel TENS (Chinese, model 7000) was used to provide TENS treatment. Treatments were carried out 3 times a week for 3 consecutive weeks.

Conventional transcutaneous electrical nerve stimulation

The ConTENS group received treatments for 30 min on the OA affected knee. Electrodes are positioned at selected points widely accepted for acupuncture treatment (acupoints) of knee pain, namely Liangqiu (ST34), Zusanli (ST36), Yinlingquan (SP9), Xuehai (SP10) and Yanglingquan (GB34). [17] Acupuncture points are selected because they were highly reproducible and convenient. [17] ConTENS treatment was delivered at 100 Hz with a pulse width of 200 us. The intensity of the current was set at a comfortable level as determined by each participant and ranges between 25 mA and 35 mA. The intensity of the current was increased at 5 min into the stimulation and/or whenever participants reported accommodation to the stimulation.

Acupuncture-like transcutaneous electrical nerve stimulation

Participants in the AcuTENS groups received TENS treatment for a total of 30 min. Electrodes placements are similar to as described above. The following TENS variables are used: Lowest rate/frequency possible (2 Hz), the highest intensity that will be tolerable for the subject for 30 min. Whenever the subject could tolerate the highest intensity stimulation, the duration of the pulse will be increased to the point of tolerance. Tolerance was defined as the level at which the participants ask the investigator to stop increasing the stimulation.

Placebo transcutaneous electrical nerve stimulation

Participants in the PlaTENS group intervention was identical to the ConTENS treatment group, but the circuit was disconnected such that when the TENS machine was turned on, an indicator light, light up; however, there was no electrical output.

Soft tissue massage

Massage treatments to the thigh and the knee joint area was administered to the participants in all the groups in this study. Techniques of soft tissue massage used were as described by Clay and Pound. [18] Subjects are positioned in half sitting or supine lying position with proper pillow support at the back of the head and the knee. Massage treatment was carried out for 5 min, 3 times weekly for 3 weeks.

Data analyses

Descriptive statistics of mean and standard deviation were used to summarize data on pain intensity, range of motion and functional mobility. Repeated measures analysis of variance (ANOVA) was used to analyze the changes in the NRS, knee range of movements and functional mobility scores among the groups. Level of significance was set at P < 0.05. After detection of significant changes in the overall time course with repeated measures ANOVA, a post-hoc analysis was carried out with Boferroni's correction.

  Results Top

A total of 27 participants met the inclusion criteria, 10 participants each were randomized into the conTENS and AcuTENS groups while 7 participants were randomized into the PlaTENS group. The total dropout rate was the same in every group with one participant in each group. Participants did not give any reason for the dropout. Thus, 9 participants were present in each of the ConTENS and AcuTENS groups and 6 participants were present in the PlaTENS group at the end of the 3 weeks of treatment and at 4 weeks follow-up assessment [Figure 1].
Figure 1: Participants flow chart

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Age and body mass index (BMI) of the participants of the three groups are presented in [Table 1]. ANOVA did not show any significant difference in the age and BMI of the participants among the three groups (P > 0.05). The pain intensity profile of the participants is presented in [Table 2]. Participants in the ConTENS and AcuTENS groups experienced reduction in the pain intensity during intervention and at follow up. However, AcuTENS group recorded greatest pain reduction during intervention and at follow up stages with pain intensity scores of 4.88 ± 1.53 at the end of the 1 st week of treatment, 2.55 ± 1.42 at the end of 2 nd week of treatment, 1.44 ± 1.23 at the end of 3 rd week of treatment and 1.34 ± 1.53 at 4-week follow up assessment. ANOVA test showed significant difference during intervention and at follow up (P < 0.05). Post-hoc analysis of the pain intensity scores showed statistically significant difference in pain intensity scores between AcuTENS and ConTENS groups at 2 nd week, 3 rd week of treatment and at follow up assessment (P < 0.05). In a similar vein, statistically significant difference in the pain intensity scores between the AcuTENS and PlaTENS groups were present at all stages of data collection during intervention and at follow up assessment (P < 0.05). Conversely the ConTENS and PlaTENS groups did not show statistical significant difference in the pain intensity scores at all stages of data collection during intervention and at follow up (P > 0.05) [Table 3].
Table 1: Demographic characteristics of the participants

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Table 2: Participants pain intensity scores

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Table 3: Post-hoc analysis of the pain intensity scores

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[Table 4] shows the mean scores for the functional mobility of the participants in each group. AcuTENS and ConTENS group showed improvement in functional mobility with functional mobility test scores progressively reduced from the 1 st week of treatment to follow up assessments in the AcuTENS group and ConTENS group. However, ANOVA test carried out on post intervention functional mobility score did not show a significant difference among the three groups at all stages of data collection (P > 0.05).
Table 4: Participants functional mobility scores

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Effects of intervention on active range of knee flexion are presented in [Table 5]. Surprisingly, participants in all the groups demonstrated the full range of active knee extension at all stages of data collection. The AcuTENS group recorded the highest increase in the active range of knee flexion at the end of the 1 st week of treatments (126.66 ± 8.29), 2 nd week of treatment (131.11 ± 6.50), 3 rd week of treatment (134.44 ± 1.66) and at follow up assessment (135 ± 8.39). Statistically significant difference in the active knee range of flexion was recorded at 3 weeks of treatment between conTENS and AcuTENS (P = 0.028) and between AcuTENS and PlaTENS (P = 0.008) [Table 6].
Table 5: Participants active range of knee flexion scores

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Table 6: Post-hoc analysis of the participants active knee fl exion score

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  Discussion Top

The present study assessed the effects of AcuTENS and ConTENS on knee OA. The AcuTENS and the conTENS groups showed decreases in pain intensity (NPRS scores) compared to the PlaTENS during treatment and at follow up assessments. The AcuTENS treatment groups showed overall statistically significant greater improvement than PlaTENS with pain reduction at all stages of data collection. Conversely, comparison of the pain intensity scores between ConTENS and PlaTENS did not show statistical significant difference. Furthermore, the AcuTENS group showed greater improvement with functional mobility and range of knee flexion than either of the conTENS or PlaTENS group. These results suggest AcuTENS treatment was significantly more effective than ConTENS in the management of knee OA.

The results of the present study in terms of the analgesic effect of TENS treatment corroborate findings from previous studies [19],[20] Ng et al. [19] carried out a randomized control trial on 24 patients to examine the relative effectiveness of electro-acupuncture (EA) and TENS in alleviating OA-induced knee pain. The result of their study showed greater reduction in pain intensity and functional mobility in the EA and the TENS groups' immediately after intervention. However, improvement in functional mobility was maintained only in the EA group at 2 week follow up assessment, which was not seen in the TENS group. Itoh et al. [20] investigated the effects of using either acupuncture treatment and/or ConTENS treatment alone or in combination on 32 patients with knee OA. Findings from their study showed the ConTENS group recorded a decrease in pain intensity and improvement in knee function, which showed no statistical significant difference from the control group.

Conventional TENS was developed in the early 1970 as a result of the gate theory of pain. For analgesia to occur according to this theory, large diameter afferents (type 1 muscle afferents and A beta skin afferents) are stimulated at low intensity and high frequency in the same dermatome as the site of the pain. This release glutamate and γ-amino-butyric acid to cause presynaptic inhibition of adjacent pain fibers (small diameter A delta and C afferent fibers) to prevent nociceptive stimuli from reaching the spinal cord transmission neurons. This form of analgesia starts within 100 ms of TENS stimulation and disappear within seconds of turning off the machine. [11] The transient nature of the analgesic effects of ConTENS perhaps could be part of the reasons why the seemingly reduced pain intensity levels of the participants in the ConTENS group in the present study did not differ significantly from the pain intensity level of the participants in the placebo group after intervention and at follow up assessments.

Conversely, an essential feature of AcuTENS is the use of strong stimulation to produce strong sensation otherwise known as de qi (this is similar to the sensations obtainable with the use of acupuncture needles). AcuTENS are stimulated at low frequency and high intensity. In general, de qi occurs with current or voltage stimulation, which is 5-10 times the threshold value for muscle contraction. The intensity is kept below the level at which patient find it intolerable and hence that a pleasant mild aching sensation is felt. [11] AcuTENS can be given as little as twice weekly with lasting effects because of endorphin release, whereas ConTENS must typically be used throughout the day to obtain sustained analgesia. Although weaker stimulation by the ConTENS can release some endorphins, the stronger intensities of AcuTENS recruit type III fibers, causing greater and longer lasting analgesic effects. In addition, ConTENS is mainly segmental in nature, not involving pituitary mechanisms. In contrast AcuTENS combine segmental and non-segmental effects. [11] It involves the brain stem, pituitary plus segmental mechanisms through endorphins and serotonin. AcuTENS usually takes 20-30 min to reach a maximum effect and the analgesia outlasts the therapy by several hours or days. [11] This perhaps could be responsible for the sustained pain reduction at follow up assessments observed in AcuTENS group, which was not present in the ConTENS group.

  Conclusion Top

The results of the present study have shown that AcuTENS treatment is more effective than ConTENS for pain relief and improvement in active knee range of movements in patients with knee OA. Large scale clinical trials are warranted.

  References Top

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  [Figure 1]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]


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