Specific manipulative therapy treatment for chronic lateral epicondylalgia produces uniquely characteristic hypoalgesia

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1 Manual Therapy (2001) 6(4), doi: /math , available online at on Original article Specific manipulative therapy treatment for chronic lateral epicondylalgia produces uniquely characteristic hypoalgesia B. Vicenzino*, A. Paungmali*, S. Buratowski {, A. Wright { *The University of Queensland, St Lucia, Australia, { Private practitioner, Queensland, Australia, { Division of Physiotherapy, Curtin University of Technology SUMMARY. The treatment of lateral epicondylalgia, a widely-used model of musculoskeletal pain in the evaluation of many physical therapy treatments, remains somewhat of an enigma. The protagonists of a new treatment technique for lateral epicondylalgia report that it produces substantial and rapid pain relief, despite a lack of experimental evidence. A randomized, double blind, placebo-controlled repeated-measures study evaluated the initial effect of this new treatment in 24 patients with unilateral, chronic lateral epicondylalgia. Pain-free grip strength was assessed as an outcome measure before, during and after the application of the treatment, placebo and control conditions. Pressure-pain thresholds were also measured before and after the application of treatment, placebo and control conditions. The results demonstrated a significant and substantial increase in pain-free grip strength of 58% (of the order of 60 N) during treatment but not during placebo and control. In contrast, the 10% change in pressure-pain threshold after treatment, although significantly greater than placebo and control, was substantially smaller than the change demonstrated for pain-free grip strength. This effect was only present in the affected limb. The selective and specific effect of this treatment technique provides a valuable insight into the physical modulation of musculoskeletal pain and requires further investigation.. INTRODUCTION Chronic lateral epicondylalgia or tennis elbow is a common musculoskeletal condition that has a prevalence rate of 3% in the general population, 15% in high risk groups (i.e. repetitive hand tasks, sports, occupational activities) (Allander 1974; Ranney et al. 1995), and accounts for approximately 7 per 1000 patient visits to a general medical practitioner (Verhaar 1992). The condition is characterized by pain over the lateral epicondyle, marked functional impairments, mechanical hyperalgesia, motor control deficits, and muscle strength changes (Wright et al. Received: 26 March 2001 Revised: 7 June 2001 Accepted: 17 July 2001 Bill Vicenzino, PhD, MSc, Grad Dip Sports Phty, B Phty, Senior lecturer, Aatit Paungmali MPhtyStudies (Orthopaedic Phty), BPhty (Hons), PhD candidate in Physiotherapy, Department of Physiotherapy, The University of Queensland, St Lucia, Australia. 4072, Sally Buratowski, BPhty (Hons), Private Practitioner, Nerang, Queensland, Australia, Anthony Wright, PhD, MPhty Studies (ManipPhty), BPhty (Hons), Professor, Division of Physiotherapy, Curtin University of Technology, Australia, Correspondence to: BV, Tel.: (61) ; Fax: (61) ; b.vicenzino@shrs.uq.edu.au 1992; Haker 1993; Stratford et al. 1993; Wright et al. 1994; Vicenzino & Wright 1996; Pienimaki et al. 1997). It is frequently employed as a clinical model of musculoskeletal pain in the study of physical treatments (Burton 1988; Stratford et al. 1989; Stratford et al. 1993; Haker 1993). The aetiology of the condition is not fully understood and although many treatments have been advocated, none are supported by high level evidence (Labelle et al. 1992; Wright & Vicenzino 1997). Subsequent to the reviews of Labelle et al. (1992) and Wright and Vicenzino (1997), the efficacy of two physical therapy modalities have been reported. Pienimaki et al. (1996), in a high quality randomized clinical trial that rates 82% on methodological rating scale of The Physiotherapy Evidence Database (PEDro, University of Sydney, New South Wales, Australia), 1 have shown that a progressive program of stretching and strengthening exercises were superior to pulsed ultrasound. Drechsler et al. (1997) performed a study of manual therapy of the radio-humeral joint and radial nerve, comparing this treatment to a treatment program of ultrasound, 1 A Paungmali is a certified rater for the PEDro scale. 205

2 206 Manual Therapy transverse friction massage and stretching and strengthening exercises for the extensors of the wrist. They demonstrated that manual therapy of the radiohumeral joint and the radial nerve produced greater improvements in recreational and occupational activity status and upper limb tension test IIb. However, this study was only of an acceptable, not high standard, as it only scored 64% on the PEDro methodology scale. Recently, a new manipulative therapy treatment technique termed Mobilization-With-Movement has been developed by Mulligan (1995). The mobilization-with-movement treatment for lateral epicondylalgia involves both manual therapy and active muscle exercise of the forearm extensors, both physical therapies that have been recently proven efficacious when applied as mono-therapies (Pienimaki et al. 1996; Drechsler et al. 1997). Specifically, the treatment involves the application of a lateral glide to the elbow joint which is sustained while an exercise, activity or movement is performed. Usually this is a gripping action of the hand (Mulligan 1995; Vicenzino & Wright 1995; Exelby 1996). This treatment technique appears to be highly efficacious in that a deficit of some 150 N grip strength from a maximum grip strength of 200 N can be immediately rectified within a treatment session and maintained after as few as 4 treatment sessions (Vicenzino & Wright 1995). Perhaps the most remarkable aspect of this rapid ameliorative effect is that it typically occurs in cases of lateral epicondylalgia of long-standing duration that are recalcitrant to other forms of treatment. To date, this evidence is of a low level being reported in clinical case studies, case series and in a preliminary placebo-controlled study (Vicenzino & Wright 1995; Abbott et al. 2000a,b; Vicenzino et al. 2000a). There is a clear need for a controlled clinical trial to evaluate the rapid pain-relieving effects of this treatment technique. The mechanism(s) by which manual physical therapy exerts its ameliorative effects in clinical practice remains to be fully elucidated. A number of studies have shown that spinal manipulative therapy evokes a specific hypoalgesic effect. Manipulationinduced hypoalgesia appears to be non-opioid in nature, that is, it is not reversed by naloxone (Zusman et al. 1989; Vicenzino et al. 2000b) and does not develop tolerance to repeated stimulation (Souvlis et al. 1999). It occurs concurrent to changes in sympathetic and motor systems and parallels the changes in these systems during stimulation induced analgesia from the lateral periaqueductal midbrain gray (Bandler & Shipley 1994; Bandler & Keay 1996). Furthermore, preliminary evidence indicates that it preferentially produces mechanical hypoalgesia as opposed to thermal hypoalgesia in both symptomatic and asymptomatic study populations (Vicenzino et al. 1995; Vicenzino et al. 1998). This specific effect Manual Therapy (2001) 6(4), produced by manipulative therapy is consistent with other findings that indicate that different physical stimuli evoke specific analgesic effects. For example, it would seem that transcutaneous nerve stimulation, a physical treatment, produces preferential reductions in thermal but not mechanical pain (Somers & Clemente 1996, 1998). High frequency electroacupuncture stimulation appears to be non-opioid in nature as opposed to low frequency which is opioid mediated (Karavis 1997). Much of the manipulative therapy research to date has focused on treating spinal motion segments with oscillatory passive mobilizing or high velocity thrust procedures. There is a dearth of information of manipulative therapy techniques for the peripheral joints. These techniques need to be investigated because conditions of the peripheral musculoskeletal system are as important as those of the spine. The primary aim of this study was to determine whether the mobilization-with-movement treatment technique for lateral epicondylalgia produced a specific and substantial initial hypoalgesic effect that was greater than the placebo or control conditions. Secondary aims were to determine if there was any difference in effect between affected and unaffected limbs and to evaluate if there was any influence of the dependent variable on the treatment effect. This work was designed to further improve knowledge of the pain-relieving effects of physiotherapy treatments. METHODOLOGY To reduce the effects of an error variance due to participant heterogeneity (individual variation) and strengthen internal validity, a randomized, repeated measures, double-blind, placebo-controlled trial was used. Subjects Seventy-two experimental sessions were conducted to investigate the effects of the mobilization-with-movement treatment technique for the elbow on pain thresholds. Twenty-four volunteers (10 female, 14 male) reporting unilateral lateral epicondylalgia of greater than 6 weeks participated in this study (Wright et al. 1992; Vicenzino et al. 1996; Smith et al. 1999). Lateral epicondylalgia was diagnosed clinically by an experienced post-graduate trained physical therapist as pain provoked on digital palpation over the lateral epicondyle and on gripping a hand dynamometer. In addition, pain had to be experienced over the lateral epicondyle in at least one of the following tests: resisted static contraction of the wrist extensors or extensor carpi radialis brevis; or stretching of the extensor muscles of the forearm (Haker 1993; Stratford et al. 1993). The major

3 Manipulative therapy treatment for chronic lateral epicondylalgia 207 Table 1. Characteristics of subjects (n ¼ 24) at the time of enrolment into the study expressed as mean+standard error of the mean Age (range, years) Duration of condition (range, 2 36 months) Right arm dominant 82.6% Right arm affected 73.9% Affected arm Unaffected arm Pain-free grip strength (N) Pressure-pain threshold (kpa) features of subjects who participated in the study are shown in Table 1. There was a 64% deficit in painfree grip strength on the affected side compared to the unaffected side and a 46% reduction in pressure-pain threshold. These subjects were recruited by a combination of media releases to the public in the metropolitan and suburban areas, and from an established network of physiotherapy clinics. Subjects were excluded if they had concomitant problems in the neck or upper limbs rather than lateral epicondylalgia (Maitland 1986, 1991). Other exclusion criteria were: neurological impairment, previous experience of manipulative therapy to the elbow joint (to reduce bias from subject s expectation), aversion to manual contact as assessed on a pre-experimental physical examination, health conditions which preclude manipulative therapy (e.g. osteoporosis, diabetes, haemophilia) (Tobis & Hoehler 1986; Lewit 1999) and concurrent use of certain medications such as analgesic or anti-inflammatory drugs. The Institutional Review Board granted ethical clearance for this study and all subjects provided written consent to participate in the study. Outcome measures (dependent variables) Pain-free grip strength Pain-free grip strength is a valid and sensitive measurement to detect change exhibited in subjects who have lateral epicondylalgia (Stratford et al. 1993; Vicenzino et al. 1996). It was measured by an electronic digital dynamometer (MIE Medical Research Ltd., Leeds, UK) with the upper limb placed by the subject s side in a standardized position of elbow extension and internal rotation of the upper limb such that the palmar aspect of the hand faced posteriorly. The subject was informed to stop squeezing the adjustable dynamometer handles when the pain was first provoked, i.e. at pain threshold (Stratford et al. 1993). Three measures of pain-free grip strength were recorded with a 30 second rest interval between each measurement. Intratester reliability of the pain-free grip strength test in this study, which was determined from the pre-test period of each experimental session, revealed a high intratester reliability with an intraclass correlation coefficient (ICC) of 0.98 and a standard error of the measurement of 1.03 N. Pressure-pain threshold An electronic algometer (Somedic AB, Farsta, Sweden) was used to measure pressure-pain threshold over the tenderest area of the lateral epicondyle. The algometer consists of a 1 cm 2 rubber tipped plunger mounted on a force transducer. The pressure was applied at a rate of 40 kpa/sec. The test was terminated at the subject s perception of the first onset of pain (Brennum et al. 1989; Vanderweeen et al. 1996). Pressure-pain threshold was measured 3 times with an approximately 30 second rest period between each measurement. The intratester reliability for pressure-pain threshold measurements in this study was also considered to be excellent with an ICC of 0.95 and a standard error of the measurement of 7.08 kpa. Experimental conditions (independent variables) There were 3 independent variables: treatment condition, side and time. Treatment condition had 3 levels, which were the treatment technique, a placebo technique and a control condition. Side had 2 levels, which were the affected and unaffected arms. The time variable differed for the dependent variables, largely as a function of the testing procedures and the treatment technique being investigated. Pain-free grip strength test can be measured during the application of the mobilization with movement treatment technique whereas pressure-pain threshold cannot. Consequently for pain-free grip strength there were 3 levels of the time variable: pre-application of the treatment conditions, as well as during and after their application. For pressure-pain threshold the time variable had 2 levels: pre- and post-application. The three treatment conditions consisted of: the treatment technique; a lateral-glide mobilization with movement treatment technique for the elbow (Mulligan 1995), was applied by an experienced manipulative physiotherapist using one hand to glide the proximal forearm laterally while the other hand fixed the distal end of the humerus (Fig. 1). The glide was applied and sustained while the subject performed the pain-free gripping action. The lateral glide was released after the subject had completed the painfree grip exercise. Six repetitions were performed with a 15 second rest interval between repetitions (Vicenzino & Wright 1995). The placebo technique was the application of firm manual contact over the subject s elbow, applied by the same manipulative physiotherapist. The manual contact was not specifically placed over the medial proximal forearm and lateral distal arm, but directly over the elbow joint on both sides. Manual Therapy (2001) 6(4),

4 208 Manual Therapy Fig. 1 The mobilization-with-movement treatment technique for the elbow joint in which a lateral glide is manually applied to the elbow and then sustained while the subject performs a pain-free grip strength test. The dynamometer handles on which pain-free grip strength is measured are also shown in situ. The control condition involved no manual contact between the therapist and the subject. The subject remained in a similar position as during the treatment and placebo techniques. Experimental procedure Subjects attended a preliminary session for screening using the inclusion and exclusion criteria, and also received instructions and familiarization with the laboratory environment and test procedures. Then, each subject attended three experimental sessions on three different days at least 48 hours apart and at about the same time of the day. At each experimental session the subject experienced one of the treatment conditions (i.e. treatment, placebo and control) in a randomized order previously determined by drawing lots. The study was conducted in an environmentcontrolled laboratory (i.e. constant temperature and humidity). The subjects were requested to avoid factors that may interfere with the outcome measures of pain perception such as taking analgesic drugs approximately 8 hours prior to the experiment (Max & Laska 1991; VDUAC 1997) and heavy exercise about 4 hours prior to the experiment (Bartholomew et al. 1996; Koltyn et al. 1996; Koltyn 2000). Their adherence to these prohibitions was assessed by means of a questionnaire prior to each experimental session and if a lapse in any of them had occurred the subject was re-scheduled for another session. As per laboratory protocol any subject who failed to meet these prohibitions on 2 occasions were excluded from the study. No subject was excluded on this basis in this study. At each experiment session, after completing the pre-session questionnaire, the subject was positioned Manual Therapy (2001) 6(4), in a supine position for the duration of the session. Pain-free grip strength and pressure-pain threshold were first measured on the unaffected side to familiarize the subject with the measurement. One of the treatment conditions (i.e. treatment, placebo or control) was then applied to the affected arm. Painfree grip strength was measured during the application of this treatment condition. Following the application of the treatment condition both dependent variables (i.e. pain-free grip strength, pressurepain threshold) were once again measured, first on the affected side and then on the unaffected side. The same treatment condition was then applied to the unaffected arm and the pain-free grip strength measured concurrently. Following this the outcome measures were repeated on the unaffected limb. Subjects were then reminded of their next experiment session time and of the prohibitions listed above. This procedure was repeated another 2 times until each subject had experienced all 3 treatment conditions in a concealed, randomized order. An experienced manipulative physiotherapist applied the mobilization technique and randomized the order of the application of treatment, placebo and control techniques. Another investigator measured the experimental outcome measures and was blind to the applied conditions in the laboratory. The therapist remained blind to the results of the tests of the outcome measures. Subject blinding was facilitated by recruiting subjects who had no previous experience of manipulative therapy of the elbow joint and by use of careful instruction that did not refer to the study s aims of investigating a treatment technique. Subjects were informed that the study was investigating the effects of manual handling and positioning of the elbow on pain thresholds. Feedback on performance on the pain tests was not provided to the subjects until the end of the experiment, and then only on request. All subjects were informed of the true nature of the study at the end of their three experimental sessions. The adequacy of subject blinding was assessed by a postquestionnaire. Data analysis The triplicate measures of pain-free grip strength and pressure-pain threshold were averaged prior to further analysis. The questions being addressed by this study were: does a treatment technique produce improvements in pain threshold measures that exceed those of placebo and control; is this effect present in the affected and unaffected arms and does it occur immediately during and after the application of the treatment? The initial statistical analysis used to address these questions was an omnibus, 3-way within-subjects analysis of variance (ANOVA), which evaluated the third-level

5 Manipulative therapy treatment for chronic lateral epicondylalgia 209 interaction effects of the three independent variables. The three independent variables for the dependent variable of pain-free grip strength were: treatment conditions with three levels (i.e. treatment, placebo and control); side-treated with two levels (unaffected or affected); and time of testing with three levels (i.e. pre-, during and post-application). The independent variables for the analysis of pressure-pain threshold data differed only in that there were only two levels for the time of testing, i.e. pre- and post-application. Following the 3 way ANOVA, pain-free grip strength data during and following the application of the treatment conditions were expressed as a percentage change from pre-application data. This served to determine effect sizes for each individual and allowed the direct comparison of these effects between the levels of the independent variables. This simple transformation also subsumes variation effects between subjects. A 2-way within-subjects ANOVA with pre-specified, within-subject contrasts was performed to analyse the pain-free grip strength data. The main effects for this analysis were treatment conditions (i.e., treatment, placebo and control) and time of testing (i.e. during application and post application percentage change from pre-application values). A one way within-subjects ANOVA with prespecified, within-subject contrasts analysed the main effect of treatment conditions (i.e. treatment, placebo and control) for the percentage change in pressurepain threshold following the application of the experimental conditions. All pre-specified contrasts involved comparisons between treatment and placebo and between treatment and control. Statistical significance was determined at the a-level of RESULTS Fig. 2 The interaction plot for pain-free grip strength (N) between treatment condition (treatment, placebo and control), time (pre, during and post-application of the experimental conditions), and side-affected (white shapes) and unaffected (dark shapes). & Pre, ~ During, * Post, & Pre, ~ During, * Post. Interaction between the main effects of experimental condition, side and time There was a statistically-significant three-way interaction effect between the independent variables of treatment condition (i.e. treatment, placebo and control), side (i.e. unaffected and affected) and time (pre-, during and post-application) for pain-free grip strength (F 4,92 ¼ 15.95, P ). The interaction plot is shown in Figure 2. On the affected side, treatment produced a substantial increase in pain-free grip strength from a mean N at baseline to N during its application period and N following its application. Pain-free grip strength values during and after intervention did not change from baseline in the placebo and control conditions. On the unaffected side, in contrast to the effects observed on the affected side, there was a reduction in pain-free grip strength value during and after the application of the mobilization-with-movement treatment technique, placebo and control on the unaffected side (Fig. 2). Pain-free grip strength decreased from a mean N, N and N before treatment, placebo and control, respectively, to N, N and N following the application of the treatment, placebo and control conditions, respectively. However, there were no statistically significant differences between conditions for the unaffected side (F 2,46 ¼ 0.14, P ¼ 0.87). No further analysis of this data was pursued. Pressure-pain threshold data did not show a significant three way interaction effect, possibly due to the effect size and power being low ( 2 ¼ 0.066, Power ¼ 0.165, F 2,46 ¼ 0.75, P ¼ 0.47). Treatment condition and time effects on pain-free grip strength on the affected side The treatment technique produced an immediate increase in pain-free grip strength of 57.58% from pre-application values during its application. Placebo produced a 10.32% increase in pain-free grip strength and control produced a 5.58% reduction (Fig. 3). The pre-specified contrasts revealed a significant difference between the effects of treatment and placebo (F 1,23 ¼ 15.84, P ¼ 0.001), and the effects of treatment and control (F 1,23 ¼ 39.65, P ). A similar pattern was also noted for pain-free grip strength in the post-application period. There was a 45.67% increase in pain-free grip strength for the treatment technique, a 9.74% increase with the placebo technique, and a 2.69 % reduction under the control condition (Fig. 3). The a-priori contrasts between treatment and placebo and between treatment and control were statistically significant (F 1,23 ¼ 12.46, P ¼ and F 1,23 ¼ 34.29, P , respectively). There was no significant effect of time on the changes in pain-free grip strength produced by the treatment conditions (F 1,23 ¼ 0.70, P ¼ 0.41). That is, the effect produced during the application of the Manual Therapy (2001) 6(4),

6 210 Manual Therapy Fig. 3 Changes in pain-free grip strength (PFG) and pressurepain threshold (PPT) of the affected side expressed as a percentage change from pre-application for treatment, placebo and control conditions (mean+standard error of mean). & Treatment, Placebo, & Control. treatment conditions (i.e. treatment, placebo and control) was sustained immediately after application. Treatment condition and time effects on pressure-pain threshold on the affected side Pressure-pain threshold data demonstrated an increase of approximately 10.26% following application of the treatment technique which was significantly greater than the 3.88% reduction in pressure-pain threshold produced by placebo (F 1,23 ¼ 7.23, P ¼ 0.01) and significantly greater than the 0.31% change following the control condition (F 1,23 ¼ 4.34, P ¼ 0.049) (Fig. 3). Drop-out rate All 24 subjects completed all 3 experimental sessions of the study. Subject blinding The post-experimental questionnaires were assessed to determine the success of subject blinding. No subjects were able to identify the treatment procedure as the real aim of the study. Complication report This study involved measurements of pain thresholds and manual techniques, so subjects were informed to immediately report to the investigators if they had any experience of pain during or after experimental period. No pain or complications were reported. DISCUSSION Manual Therapy (2001) 6(4), This study demonstrated a rapid and substantial hypoalgesic effect during and following the application of the mobilization-with-movement treatment technique for lateral epicondylalgia. The hypoalgesic effect was specific in that it only occurred with the application of the mobilization-with-movement treatment technique, not with the placebo and control conditions and also only when applied to the affected arm, not the unaffected arm. The significantly greater effect following a manual therapy treatment technique applied to a peripheral joint corroborates the findings of previous studies of manual physical therapy treatments of the spine (Zusman et al. 1989; Vicenzino et al. 1995; Vicenzino et al. 1996; Vicenzino et al. 1998; Vicenzino et al. 2000b; Sterling et al. 2000). However, the differential in effect between affected and unaffected arms differs to previouslydocumented research of spinal manipulative therapy in which treatments also exerted hypoalgesic effects in asymptomatic subjects (Terret & Vernon 1984; Vicenzino et al. 1995), possibly denoting a difference between manual therapy of spinal and peripheral joints. The specificity of treatment induced hypoalgesic effect was further exhibited by way of a differential effect in the two outcome measures. The mobilization-with-movement treatment technique produced an improvement in pain-free grip strength during treatment of 58% with a non-significant reduction in this effect to 46% improvement immediately following treatment compared to a 10% improvement in pressure-pain threshold immediately following treatment. This effect profile contrasts to that of the lateral glide technique of the cervical spine, a spinal manipulative therapy technique for lateral epicondylalgia that has been previously investigated. The lateral glide of the cervical spine produced an improvement in pain-free grip strength of the order of 12 to 30% and an improvement in pressure-pain threshold of approximately 25 to 30% immediately following treatment (Vicenzino et al. 1995; Vicenzino et al. 1998). This difference may be due to the different body regions being manipulated (i.e. elbow versus cervical spine) because previous studies of manual therapy have shown that the area of body being treated influences the outcome (Harris & Wagnon 1987; Slater & Wright 1995; Vicenzino et al. 1998; Dahl et al. 2000). Another possible reason for different effect profiles between the mobilization-with-movement treatment technique of the elbow and the cervical spine lateral-glide technique is the frequency profile of the techniques. The former is a sustained static manual technique (i.e. 0 Hz) as opposed to a Hz oscillation for the latter (Vicenzino et al. 1999). The frequency profile of a physical treatment technique has been shown to influence the outcomes it produces (Chiu & Wright 1996; Karavis 1997; Ghoname et al. 1999). The different effect profiles of manual therapy techniques concurs with evidence of specific hypoalgesic effects

7 Manipulative therapy treatment for chronic lateral epicondylalgia 211 of other physical treatments such as transcutaneous electrical nerve stimulation and electroacupuncture (Han et al. 1991; Chen & Hen 1992; Karavis 1997) and further supports the assertion that the mechanisms by which these treatments evoke their hypoalgesic effects are probably complex. The unaffected side exhibited a reduction of painfree grip strength values from the pre-application period for all treatment conditions. This may have been due to a fatigue effect since on the unaffected side the grip strength test was not limited by pain but rather it was a test of maximum grip force. The treatment technique was not able to arrest the decline in grip strength on this side, possibly indicating that the underlying mechanism of action of the treatment is not peripherally based. This study documented the effect of a mobilizationwith-movement treatment technique on pain-free grip strength during the application of the technique, and pain-free grip strength and pressure-pain threshold immediately after its application. The time course of therapeutic effects following mobilization-with-movement treatment remains to be evaluated. The mobilization-with-movement treatment technique is a combination of manual therapy (manual sustained lateral glide of the elbow) and therapeutic exercise (repeated gripping action), both of which have proven efficacy in treating lateral epicondylalgia. The mobilization-with-movement treatment technique appears well-suited to ameliorate the pain and dysfunction of chronic lateral epicondylalgia because the largest treatment effect was observed in pain-free grip strength and functional activities involving gripping actions of the hand are markedly impaired in individuals who have lateral epicondylalgia. Additionally, there were no adverse effects reported in the short-term, implying that the technique is both safe and effective in producing pain relief. CONCLUSION This study provides evidence of the initial and substantial pain-relieving effects of a mobilizationwith-movement treatment technique for chronic lateral epicondylalgia. In keeping with other studies on physical treatments and stimuli, the effect is specific to the dependent variable with changes in pain-free grip strength outweighing by a factor of 5 the changes in pressure-pain threshold. Also the treatment technique only achieved this effect when applied to the affected arm, not the unaffected arm. Further investigation of these pain-relieving effects will improve our understanding of the pain-control mechanisms activated by manipulative therapy and improve the non-surgical management of lateral epicondylalgia. 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