Research Report
TRANSCUTANEOUS ELECTRICAL NERVE STIMULATION AND INTERFERENTIAL CURRENT COMBINED WITH EXERCISE FOR THE TREATMENT OF KNEE OSTEOARTHRITIS: A RANDOMISED CONTROLLED TRIAL Rufus A. Adedoyin, RA PhD; Matthew O.B. Olaogun, MOB MS; Adewale L. Oyeyemi,1 AL BMR
Abstract: Interferential current (IFC) and transcutaneous electrical nerve stimulation (TENS) are forms of electrical stimulation frequently used to treat knee osteoarthritis (OA). The relative effectiveness of these two modalities is currently unknown. The purpose of this study was to evaluate the effects of IFC and TENS, when used in conjunction with exercise, on pain and function in patients with knee OA. Forty-six subjects with radiographically confirmed OA were randomly assigned to one of three groups: TENS and standardised exercises, IFC and exercises or exercises alone. An electrical stimulator was used to apply IFC or TENS at 80 Hz for 20 minutes. All groups had a standardised exercise programme. Treatment was applied twice per week for 4 weeks. Outcomes included a 10-point pain rating scale for pain intensity and the Western Ontario and McMaster University Osteoarthritis Index (WOMAC). A two-way repeated measures ANOVA performed on the pain assessment score showed a statistically significant effect of time (p < 0.001), but not of experimental group (p = 0.813) or interaction (p = 0.067). A similar result was obtained for WOMAC score (p < 0.001, p = 0.241 and p = 0.130 for time, group and interaction effects, respectively). All treatment protocols led to significant improvements in pain and function over time. Neither IFC nor TENS displayed significant additional effects over exercise alone.
Key words: interferential current, TENS, exercise, osteoarthritis
Introduction Osteoarthritis (OA) of the knee is the most common cause of chronic disability among the elderly worldwide [1,2]. Radiographical and pathological changes of OA are present in most persons over the age of 65 years. Because the knee joint is weight bearing and contributes to ambulation, patients usually experience functional limitations in activities of daily living [3]. Although the pathomechanics of knee OA are well documented [4], the condition is still not easily treated [2]. Both pharmacological and non-pharmacological
approaches have been used with varying degrees of success [5]. Recent studies have reported that nonsteroidal anti-inflammatory drugs (NSAIDs), one of the most commonly prescribed treatments for OA, may have deleterious effects on cartilage metabolism [5,6]. Physiotherapy, however, may play a major role in the relief of pain and improvement of function in knee OA. The physiotherapy modalities commonly used include interferential current (IFC), transcutaneous electrical nerve stimulation (TENS), exercise, cold therapy, acupuncture, low-energy laser, vibration, topical gel and orthotic devices [7,8].
1
Department of Medical Rehabilitation, Obafemi Awolowo University, Ile-Ife, and Department of Physiotherapy, University of Maiduguri Teaching Hospitals, Maiduguri, Nigeria. Received: 14 February 2005. Accepted: 2 June 2005. Reprint requests and correspondence to: Dr. Rufus A. Adedoyin, Department of Medical Rehabilitation, Obafemi Awolowo University, Ile-Ife, Nigeria. E-mail:
[email protected]
Hong Kong Physiotherapy Journal • Volume 23 • 2005 ©2005 Elsevier. All rights reserved.
13
IFC and TENS are forms of electrical current that are primarily used for pain relief [9,10]. IFC is a current of approximately 4,000 Hz that rhythmically increases and decreases at a frequency of 0–250 Hz [9]. TENS is a frequency current of 1–250 Hz [11]. IFC has lower skin impedance, reducing the discomfort normally associated with low-frequency currents [12], although this assertion has been challenged [13]. Both modalities have been used to treat conditions such as OA knee pain and low back pain [14]. The relative effectiveness of these two interventions for the management of pain, however, remains unclear [9, 15–17]. A number of studies have assessed the effectiveness of IFC on OA of the knee, each demonstrating significant improvements in symptoms over time. When compared with the effects of other interventions, however, two studies failed to show benefits greater than either placebo IFC [16] or an exercise programme [18]. However, we previously reported a significantly greater effect of IFC over placebo in managing OA knee pain among black Africans [19]. The evidence for IFC in the treatment of this condition is, therefore, equivocal. Johnson presented a systematic review of TENS and TENS-like devices in relation to pain relief, and concluded that TENS may be effective in postoperative pain and labour pain [20]. However, the benefit of TENS in managing OA of the knee is inconclusive. Cheing et al found significant reductions in OA knee pain over time, but the effect was no better than exercise or sham treatment [21]. A later study by the same authors reported a significantly greater reduction in OA knee pain in patients receiving 40 minutes and 60 minutes active TENS than those receiving 20 minutes active TENS or 60 minutes placebo. They recommended 40 minutes as the optimal duration of TENS in pain reduction and post-stimulation analgesia for this condition [22]. Study of the comparative effects of IFC and TENS has, to date, been limited to laboratory studies. Salisbury and Johnson reported that IFC decreased cold pain intensity and TENS increased the cold pain threshold [23], suggesting possible differences in the action of the two modalities. Most studies, however, have failed to demonstrate differences in the effects of IFC and TENS on experimental ischaemic pain [24], cold pressor pain [25] or mechanical pain [26]. Recently, Cheing and Hui-Chan reported that both IFC and TENS were effective in reducing experimentally induced heat pain [17], although Palmer et al found no effects of either modality on a range of thermal thresholds when compared with control and placebo stimulation [27]. Despite the reported reduction in pain perception using IFC and TENS in experimental studies, evidence for their clinical use is still limited. Healthy subjects usually selected for experimentally induced pain are largely homogenous. Therefore, differences in the
14
response to treatment between groups may be more easily attributed to the intervention, rather than to individual variation [17]. Subjects with clinical pain, however, are heterogeneous, each having a different onset, clinical history, severity and concomitant conditions. All of these factors may affect the response to treatment in clinical trials. Although the evidence for other modalities is lacking, there is strong evidence for the benefits of exercise in relieving pain and improving functional status. Huang et al reported significant improvements in pain, reduced disability and improved walking speed in OA patients after a muscle-strengthening exercise programme [28]. Brosseau et al also showed that both high- and lowintensity aerobic exercise improved functional status, gait and pain in knee OA [29]. The purpose of this study was to evaluate the effects of IFC and TENS, when used in conjunction with exercise, on pain and function in patients with knee OA. We specifically combined an exercise programme with these two modalities to maximise any effect on patient pain and function.
Methods Sample size calculations Sample size was calculated on the basis of mean visual analogue scale (VAS) scores reported previously for a similar population of patients with knee OA (8.10 ( 1.23 cm) [19]. An assumption was made that a clinically significant change in VAS scores would be 30% and a significance level of 0.01 and 95% power were chosen. These criteria led to an estimated minimum sample size of 13 in each group [30].
Subjects Fifty-one subjects voluntarily participated in this study, but only 46 subjects (28 women and 18 men) with a mean age of 55.41 years (SD = 9.21) were able to complete the study. The Obafemi Awolowo University Teaching Hospital ethics committee approved the study protocol. All subjects gave signed, informed consent. Information about the study and the physiological and therapeutic effects of TENS, IFC and exercise was related to subjects, verbally and also in written form. Subjects were told that the modalities used were capable of relieving their pain. An orthopaedic physician referred all patients for physiotherapy. Subjects were selected for the study if they had radiographically confirmed unilateral OA of the knee and had not previously received electrical stimulation. Lower-quarter screening tests were conducted as described by Saunders to rule out pain referred from elsewhere [31]. Subjects with cardiopulmonary dysfunction, acute inflammation, Hong Kong Physiotherapy Journal • Volume 23 • 2005
fever, tumours or cardiac pacemakers were excluded from the study, as were pregnant women. Subjects were asked to confirm all of these conditions based on their medical records. They were asked to refrain from the use of analgesic drugs during the period of the study and all patients verbally confirmed that they had complied with this request. Subjects were randomly and exclusively assigned to one of three experimental groups: IFC and a standardised exercise programme; TENS and exercises; and exercises alone. Five subjects were excluded from the analysis due to non-completion of treatment. Two of these subjects (1 from the IFC group and 1 from the exercise group) withdrew from the study. The other three subjects (2 from the IFC group and 1 from the exercise group) missed appointments due to transportation problems. Forty-six subjects (28 women and 18 men; mean age, 55.41 ( 9.21 years) completed the study and were included in the final analysis.
Procedures At the first appointment, each subject’s age, height and weight were recorded. A physiotherapist who was blinded to the subject’s treatment group conducted the assessments throughout the study and was not involved in the treatment. Each subject also completed the Western Ontario and McMaster University Osteoarthritis Index (WOMAC), which is reported to be valid for the assessment of symptoms and physical functional disability in patients with OA of the knee and hip [32]. Subjects rated the 24 questions (5 relating to pain, 2 to stiffness and 17 to function) on a five-point scale: 0 = none, 1 = slight, 2 = moderate, 3 = severe and 4 = extreme. Subjects attended two treatment sessions each week for 4 weeks (total, 8 treatments), with at least 24 hours between each treatment. WOMAC score was also assessed at the end of each week of treatment (appointment numbers 1, 4, 6 and 8). Following the WOMAC assessment, each subject was asked to stand and was introduced to a 10-point pain rating scale [33]: 0 was labelled “no pain”, 5 was labelled “moderate pain” and 10 was labelled “worst pain imaginable”. Subjects were asked to point to the number corresponding to his or her pain intensity and this was recorded. Pain rating was completed in full weight bearing and instructions were given not to under- or over-estimate their pain. These ratings were conducted at the end of every treatment session. The same physiotherapist assessed both WOMAC score and pain. Subjects were then positioned for treatment lying supine on the treatment bed with a pillow supporting the head. The knee undergoing treatment was slightly flexed and supported with a pillow. The area to be treated was cleansed with alcohol to improve skin conductivity. An electrical stimulator that could deliver both IFC and TENS (Endomed 592ID, Enraf-Nonius, Delft, the Netherlands) was used for treatment, reducing the Hong Kong Physiotherapy Journal • Volume 23 • 2005
possible influence of the appearance of different stimulators on psychological factors.
Exercise During each appointment, subjects underwent an exercise programme. The exercises included riding on a bicycle ergometer and performing isometric exercises of the quadriceps muscles. Quadriceps-muscle strengthening is a common goal in the management of osteoarthritis, preventing disuse atrophy and protecting against further progression of degenerative processes [14]. Quadriceps-strengthening exercises were performed using metallic interchangeable weights (Preston Corporation, Clifton, NJ, USA) fastened to the ankle of the affected leg. The Delorme and Watkins principle of 10-repetitive maximum (10RM) was used to determine and standardise the weight used by each subject [34]. Subjects sat on the edge of a plinth with the back fully supported and the two hands holding the edges of the plinth. Subjects performed isometric knee extension exercises from a starting position of 0$ knee flexion. The subject was helped by an investigator to lift the weight from 90$ to 180$ extensions. The extension was sustained for 10 seconds (isometric) before the leg was lowered (with help, if required) and rested for 5 seconds. Subjects repeated the exercise 10 times to make one bout. A total of 10 bouts were performed with 2 minutes rest in between bouts (total of 100 contractions) [35]. Isometric contraction was chosen because it elicits less pain than isotonic and isokinetic exercises. Each subject began with the maximum load that could be sustained for the first week and progressed in subsequent weeks, depending on the new weight that could be sustained. Two subjects (1 each from the TENS and exercise-only groups) were unable to increase the load until Week 4. All other subjects were able to increase the load as of Week 2. Subjects were not given a home exercise programme because different levels of compliance may have affected the study results. Subjects were allowed to rest for at least 5 minutes before riding the stationary bicycle ergometer with an initial resistance set at 25 W for 6 minutes. The resistance was increased to 35, 45 and 55 W in the second, third and fourth weeks, respectively. The power output chosen was based on the recommendation of Pollock and Wilmore for middle-aged, less fit and cardiac patients [36]. This progression ensured a gradual increase in demand for improved cardiovascular endurance gains and was tolerated by all subjects. We included this aerobic exercise because of its optimal benefits in healthrelated quality of life and physical function [37]. All subjects were given different appointment times so that they did not receive treatment together. While subjects in the IFC and TENS groups received electrical stimulation, subjects in the exercise-only group had 20 minutes of rest.
15
Results
IFC Two electrodes (8 =6 cm), padded with wet lint to improve conductivity, were applied to either side of the affected knee joint and aligned longitudinally along the length of the limb. The electrodes were secured using Velcro straps. A beat frequency of 80 Hz continuous was selected. Frequencies of 50–100 Hz have been reported as generally more comfortable than 5 Hz [8]. The current intensity was adjusted until the subject reported feeling a strong tingling sensation without causing muscle contraction. Subjects were instructed to adjust the current intensity to maintain a strong but comfortable level of stimulation throughout treatment. Each IFC treatment session lasted 20 minutes. Two treatment sessions were given every week, between 9:00 am and 11:00 am, with at least 24 hours between each session.
TENS The procedure used for the application of TENS was precisely the same as that described for IFC. Stimulation frequency was 80 Hz continuous, phase duration was 200 ms, and current intensity was strong but comfortable. A different therapist used IFC and TENS to treat all patients.
Physical characteristics Age (p = 0.708) and BMI (p = 0.100) were not significantly different in the three experimental groups (Table). The groups were therefore considered comparable, at least on these criteria. The ratio of females to males was different in the exercise group compared with the other experimental groups. The exercise group has a female to male ratio of 7:8, while IFC & Exercise and TENS & Exercise groups have a female to male ratio of 11:5 and 10:5, respectively.
Pain intensity scores There was no significant difference in baseline mean pain intensity score (F = 0.296; df = 2; p = 0.745). Time had a significant effect on change in mean pain intensity score (F = 403.652; df = 2.880*; p < 0.001), but experimental group (F = 0.208; df = 2; p = 0.813) and interaction did not (F = 2.048; df = 5.760*; p = 0.067) (Figure 1).
Table. Mean age and body mass index (BMI) for each experimental group (with standard deviation, SD)
Data analysis Separate one-way ANOVAs were used to compare age and body mass index (BMI) between groups, and to compare pain scores, total WOMAC scores and pain, stiffness and function WOMAC subscale scores between groups at baseline. Separate two-way repeated measures ANOVAs were used to examine the effects of time, group and interaction on pain rating, total WOMAC score and WOMAC subscale scores.
†
Group Exercise (n = 15) IFC & exercise (n = 16) TENS & exercise (n = 15)
‡
Age (yrs)
BMI
56.87 ( 6.53 53.20 ( 11.03 55.40 ( 9.55
26.85 ( 5.01 25.99 ( 6.19 30.30 ( 7.19
IFC = interferential current; TENS = transcutaneous electrical nerve † ‡ stimulation. F = 0.348; p = 0.708; F = 2.430; p = 0.100.
12
Exercise IFC + exercise
10-point pain rating scale
10
TENS + exercise
8
6
4
2
0 1a
1b
2a
2b
3a
3b
4a
4b
Week number
Figure 1. Mean pain intensity scores for each experimental group. IFC = interferential current; TENS = transcutaneous electrical nerve stimulation.
16
*Statistically significant Mauchly’s test of sphericity. Hong DegreeKong of freedom correctedJournal using Huynh Feldt Physiotherapy • Volume 23epsilon. • 2005
70 Exercise 60
IFC + exercise TENS + exercise
WOMAC score
50 40 30 20 10 0 1
2
3
4
Week
Figure 2. Mean WOMAC osteoarthritis index scores for each experimental group. IFC = interferential current; TENS = transcutaneous electrical nerve stimulation.
Total WOMAC index scores There were no statistically significant differences in total WOMAC scores between groups at baseline (F = 2.187; df = 2; p = 0.125). Two-way ANOVA with repeated measures showed significant changes in scores over time (F = 135.037; df = 1.804*; p < 0.001), but no significant differences between groups (F = 1.471; df = 2, p = 0.241) and no significant interaction effects (F = 1.874; df = 3.608*; p = 0.130) (Figure 2).
Discussion The present study demonstrated significant improvements in pain and WOMAC scores over a period of 4 weeks for all treatment groups. The addition of IFC or TENS to a programme of exercises alone did not, however, provide significantly improved clinical outcomes. The results of this investigation reflect those of Quirk et al [18], who also found that IFC did not significantly improve outcomes for patients with OA knee pain when compared with an exercise programme alone. Other clinical trials report similar findings. Martin et al found that the addition of active or placebo IFC to a programme of exercises and mobilisation failed to produce enhanced outcomes for patients with proximal humerus fractures [38]. Young et al also reported that IFC was no more effective than placebo in reducing the pain of patients with knee OA [16]. The findings from these studies do not, therefore, provide strong evidence for effects of IFC additional to those achievable by exercise, advice, or placebo treatment. However, in a previous study, we found that IFC, when combined with advice and a mobilisation exercise regime, was significantly better than placebo IFC in reducing pain intensity in black
Africans [19]. The present study, using a similar experimental protocol, compared the effects of IFC with another active treatment (TENS) and a control situation (exercise alone) in a further attempt to establish evidence for the effects of electrical stimulation. A recent Cochrane review concluded that TENS was more effective than placebo for the treatment of pain and stiffness in knee OA [39]. Cheing et al reported that a single session of TENS was better than exercise alone when treatment was given for 60 minutes, 5 days a week [21]. No difference, however, was recorded after 20 days of treatment, except after 4 weeks of follow-up, when the TENS group and TENS-plus-exercise group maintained a significant reduction in pain, while the placebo and exercise-alone groups had increased pain. The present investigation failed to demonstrate that TENS was any more effective than an exercise programme for the treatment of this patient group. The lack of a strict control or placebo condition in the current research prevents any clear appreciation of the analgesic efficacy of TENS in isolation, but does demonstrate a lack of an additional effect of TENS over exercise alone. As outlined in the introduction, most of the investigations directly comparing the analgesic effects of IFC with those of TENS have been in a laboratory setting and have failed to demonstrate a clear advantage of either modality. The present findings suggest that the lack of differential effects identified in the laboratory may also be evident in the clinical setting. The role of exercise in the management of OA of the knee has been substantiated by a recent Cochrane review [40]. Therapeutic exercise improves both pain and function, although there is not enough information to make recommendations on specific exercise types or dosages. Thomas et al designed a home-based exercise
*Statistically significant Mauchly’s of sphericity. Degree of freedom corrected using Huynh Feldt epsilon. Hong Kong Physiotherapy Journaltest • Volume 23 • 2005
17
programme for patients with OA knee pain [41]. In their study, 786 subjects were randomly assigned to one of four groups: exercise therapy; monthly telephone contact; exercise therapy plus telephone contact; or no intervention. There were significant improvements in knee pain for the pooled exercise groups compared with the non-exercise groups after 24 months. Topp et al found that dynamic or isometric resistance exercises produced pain relief that was significantly better than control in patients with knee OA [42]. The results of the present study support these previous observations, with a statistically significant improvement in pain and WOMAC scores over a period of 4 weeks in all treatment groups. The role of exercise in the management of OA knee pain cannot be over-emphasised. Exercise may have lasting benefits on the complex psychosocial sequelae of OA, facilitating the development of appropriate pain coping and self-management strategies that might be as important as its physiological effects [43]. It has also been suggested that greater strength may protect joints and, thereby, delay knee OA [15]. Fransen et al found no evidence for the superiority of supervised exercise classes or one-to-one exercise sessions [40]. Bischoff and Roos recommend both aerobic and strengthening exercises to improve pain and function in patients with OA [37]. Although the effectiveness of exercise in pain management may be similar to that of NSAIDs, exercise interventions are safer and improve function [40]. WOMAC has successfully been used to investigate a range of physiotherapeutic interventions [32,44] and, as such, was considered appropriate for the purposes of the present study. The analysis demonstrated significant improvements in total WOMAC scores and for each of the subscales. There were no significant differences between groups, however. The findings of this study should be interpreted with caution. The strength gained during exercise training was not monitored and, therefore, any significant changes in muscle strength over the 4 weeks of treatment could not be determined. Increased muscle strength may have a positive effect on pain and function. Furthermore, electrode placement was uniform for all subjects rather than appropriate for the pain location of each patient. It is plausible that the analgesic effects of TENS and IFC might have lasted longer than that of exercise, if we had conducted follow-up assessment after the 4-week intervention.
Conclusion The present investigation of IFC and TENS examined their effects when used in addition to an exercise programme. The outcome measures included pain intensity and the WOMAC OA Index. The results indicated that all three groups improved significantly
18
over a period of 4 weeks. There were no additional effects of IFC or TENS on pain and function, however, when compared with therapeutic exercise alone. These findings have important financial and practical implications. Exercise may play a major role in the management of patients with OA.
References 1. Guccione AA, Felson DT, Anderson JJ, et al. Specific diseases and their effects on functional limitations in elders in the Framingham study. Am J Public Health 1994;84:351–8. 2. Felson DT. The course of osteoarthritis and factors that affect it. Rheum Dis Clinic North Am 1993;19:607–15. 3. Netter FH, Freyberg R. Rheumatics’ diseases. In: Nelder FH, ed. The Gba Collection of Medical Illustrations. Gmmit SFA: CibaGeigy Corporation, 1990:178–81. 4. Martin DF. Pathomechanics of knee osteoarthritis. Med Sci Sports Exerc 1994;26:1,429–34. 5. Brandt KD. Effects of non-steroidal anti-inflammatory drugs on chondrolyte metabolism in vitro and vivo. Am J Med 1987; 83:29–34. 6. Bradley JD, Brandt KD, Katz BP, et al. Comparison of an antiinflammatory dose of ibuprofen, an analgesic dose of ibuprofen, and acetaminophen in the treatment of patients with osteoarthritis of the knee. N Engl J Med 1991;325:87–91. 7. Puett DW, Griffin MR. Published trials of non-medicinal and non-invasive therapies for hip and knee osteoarthritis. Ann Intern Med 1994;121:133–40. 8. Ezzo I, Hadhazy V, Birch S. Acupuncture for osteoarthris of the knee: a systematic review. Arthritis Rheum 2001;44:819–25. 9. Palmer S, Martin D. Interferential current for pain control. In: Kitchen S, Bazin S, eds. Electrotherapy: Evidence-based th Practice, 11 edition. Edinburgh: Churchill Livingston, 2002: 287–300. 10. Foster NE, Thompson KA, Baxter GD, et al. Management of non-specific low back pain by physiotherapists in Britain and Ireland: a descriptive questionnaire of current clinical practice. Spine 1999;24:1,332–42. 11. Johnson M. Transcutaneous electrical nerve stimulation (TENS). In: Kitchen S, ed. Electrotherapy: Evidence-based Practice. Edinburgh: Churchill Livingston, 2001:259–86. 12. Goats GC. Interferential current therapy. Br J Sports Med 1990; 24:87–92. 13. Alon G. Interferential current news. Phys Ther 1987;67:280–1. 14. Burton AK, Waddell G, Tillotson KM, et al. Information and advice to patients with back pain can have a positive effect. A randomized controlled trial of a novel educational booklet in primary care. Spine 1999;24:2,484–91. 15. Sherma L, Dunlop DD, Cahue S, et al. Quadriceps strength and osteoarthritis progression in malaligned and lax knees. Osteoarthritis Cartilage 2003;11:252–9. 16. Young SL, Wodburg MG, Friday-Field K, et al. Efficacy of interferential current stimulation alone for pain reduction in patients with osteoarthritis of the knee: a randomized placebo control clinical trial. Phys Ther 1991;71:552. (Abstract) 17. Cheing GL, Hui-Chan WY. Analgesic effects of transcutaneous electrical nerve stimulation and interferential circuits on heat pain in healthy subjects. J Rehabil Med 2003;35:15–9. 18. Quirk A, Newman RJ, Newman KJ. An evaluation of
Hong Kong Physiotherapy Journal • Volume 23 • 2005
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
interferential therapy, shortwave diathermy and exercise in the treatment of osteoarthritis of the knee. Physiotherapy 1985;7:55–7. Adedoyin RA, Olaogun MOB, Fagbeja OF. Effects of interferential current stimulation in management of osteoarthritic knee pain. Physiotherapy 2002;88:493–9. Johnson MI. Transcutaneous electrical nerve stimulation (TENS) and TENS like devices; do they produces pain relief? Pain Review 2001;8:122–58. Cheing GL, Hui-Chan CW, Chan KM. Does four weeks of TENS and/or isometric exercise produce cumulative reduction of osteoarthritis knee pain? Clin Rehabil 2002;16:749–60. Cheing GL, Tsui AY, Lo SK, et al. Optimal stimulation duration of TENS in the management of osteoarthritic knee pain. J Rehabil Med 2003;35:62–8. Salisbury L, Johnson M. The analgesic effects of interferential therapy compared with TENS on experimental cold induced pain in normal subjects. Physiotherapy 1995;81:741. Tabasam G, Johnson MI. Electrotherapy for pain relief: does it work? A laboratory based study to examine the analgesic effects of electrotherapy on cold induced pain in healthy individuals. Clin Effect Nurs 1999;3:14–24. Johnson MI, Tabasam G. A double-blind placebo-controlled investigation into the analgesic effects of inferential currents and transcutaneous electrical nerve stimulation on cold induced pain in healthy subjects. Physiother Theory Pract 1999;15:217–33. Alves-Guerreiro J, Noble JG, Lowe AS, Walsh DM. The effect of three electrotherapeutic modalities upon peripheral nerve conduction and mechanical pain threshold. Clin Physiol 2001; 21:704–11. Palmer S, Martin D, Steedman W, Ravey J. Effects of electric stimulation on C and A delta fiber-mediated thermal perception thresholds. Arch Phys Med Rehabil 2004;85:119–28. Huang MH, Lin YS, Yang RC, et al. A comparison of various therapeutic exercises on the functional status of patients with knee osteoarthritis. Semin Arthritis Rheum 2003;36:398–406. Brosseau L, Macleay L, Robinson V, et al. Intensity of exercise for the treatment of osteoarthritis. Cochrane Database Syst Rev 2003;CD004259. (Abstract) Machin D, Campbell M, Fayers P, Pinol A. Sample Size Tables nd for Clinical Studies, 2 edition. Malden, MA: Blackwell Science, 1997.
Hong Kong Physiotherapy Journal • Volume 23 • 2005
31. Saunders HA. Evaluation of musculoskeletal disorders. In: Gould JA, Davies GJ, eds. Orthopaedic and Sports Physical Therapy. St Louis: Mosby 1985:169–80. 32. McConnell S, Kolopack P, Davis AM. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC): a review of its utility and measurement properties. Arthritis Rheum 2001;45:453–61. 33. Burg GAV. Physiological bases of perceived exertion. Med Sci Sport Exerc 1982;14:377–81. 34. Delorme T, Watkins A. Techniques of progression exercise. Arch Phys Med Rehabil 1948;29:263. 35. Kisner C, Colby LA. Therapeutic Exercise: Foundation and Techniques. Philadelphia: FA Davis Company, 1990:109–46. 36. Pollock ML, Wilmore JH. Exercise in Health and Disease: Evaluation and Prescription for Prevention and Rehabilitation, nd 2 edition. Philadelphia: W.B. Saunders Company, 1990: 259–66. 37. Bischoff HA, Roos EM. Effectiveness and safety of strengthening, aerobic, and coordination exercises for patients with osteoarthritis. Curr Opin Rheumatol 2003;15:141–4. 38. Martin D, Palmer S, Heath C. Interferential current as an adjunct to exercise and mobilization in the treatment of proximal humerus fracture pain: lack of evidence of an additional effect. Physiotherapy 2000;86:147. 39. Osiri M, Welch V, Brosseau L, et al. Transcutaneous electrical nerve stimulation for knee osteoarthritis. Cochrane Database Syst Rev 2002;(1). 40. Fransen M, McConnell S, Bell M. Exercise for osteoarthritis of the hip or knee. Cochrane Database Syst Rev 2004;(1). 41. Thomas KS, Muir KR, Doherty M, et al. Home based exercise programme for knee pain and knee osteoarthritis randomized controlled trial. BMJ 2002;325:752. 42. Topp R, Woolley S, Hornyak J, et al. The effect of dynamic versus isometric resistance training on pain and functioning among adults with osteoarthritis of the knee. Arch Phys Med Rehabil 2002;83:1189–95. 43. Hurley MV, Mitchell HL, Walsh N. In osteoarthritis, the psychosocial benefits of exercise are as important as physiological improvements. Exerc Sport Sci Rev 2003;31:138–43. 44. Kennedy D, Stratford PW, Pagura SMC, et al. Exploring the factorial validity and clinical interpretability of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Physiother Can 2003;55:160–8.
19
