Experimental Low Back Pain Decreased Trunk Muscle Activity in Currently Asymptomatic Recurrent Low Back Pain Patients During Step Tasks

Low back pain (LBP) patients show reorganized trunk muscle activity but if similar changes are manifest in recurrent LBP (R-LBP) patients during asymptomatic periods remains unknown. In 26 healthy and 27 currently asymptomatic R-LBP participants electromyographic activity (EMG) was recorded from trunk and gluteal muscles during series of stepping up and down on a step bench before and during experimentally intramuscular induced unilateral and bilateral LBP. Pain intensity was assessed using numeric rating scale (NRS) scores. Root mean square EMG (RMS-EMG) normalized to maximal voluntary contraction EMG and pain-evoked differences from baseline (ΔRMS-EMG) were analyzed. Step task duration was calculated from foot sensors. R-LBP compared with controls showed higher baseline RMS-EMG and NRS scores of experimental pain (P?<?.05). In both groups, bilateral compared with unilateral experimental NRS scores were higher (P?<?.001) and patients compared with controls reported higher NRS scores during both pain conditions (P?<?.04). In patients, unilateral pain decreased ΔRMS-EMG in the Iliocostalis muscle and bilateral pain decreased ΔRMS-EMG in all back and gluteal muscles during step tasks (P?<?.05) compared with controls. In controls, bilateral versus unilateral experimental pain induced increased step task duration and trunk RMS-EMG whereas both pain conditions decreased step task duration and trunk RMS-EMG in R-LBP patients compared with controls (P?<?.05).

Diffuse noxious inhibitory control evoked by tonic craniofacial pain in humans

Tonic pain in one body segment can inhibit the perception of pain in another body segment. This phenomenon is mediated by diffuse noxious inhibitory controls (DNIC), and its efficacy in craniofacial regions is investigated in this study. A compressive device that evoked a tonic, moderate/severe, headache‐like, conditioning pain (～8/10 on a visual analogue scale) was applied for 15 min. Eleven males participated in the study. Pressure pain threshold (PPT) and pressure pain tolerance (PPTol) at multiple heterosegmental body sites (right masseter, splenius capitis, second intermediate phalange, brachioradialis and tibialis anterior) were measured before, during and at multiple time points (5, 20 and 35 min) after the termination of the conditioning pain. PPTs and PPTols were compared within participants across two experimental sessions; one that included painful conditioning stimulation, and a separate control session on a different day. Painful conditioning increased PPT significantly during pain over the masseter (p <0.05) and over the tibialis anterior (p <0.01). PPTol was unchanged. In the period after the painful conditioning stimulation PPT was depressed compared to control. This study shows that pain evoked from the craniofacial region evokes DNIC‐like mechanisms on segmental as well as heterosegmental sites.     

Effects of thermotherapy and transcutaneous electrical nerve stimulation on patients with primary dysmenorrhea: A randomized,placebo-controlled,double-blind clinical trial

ObjectivesTo evaluate the effects of thermotherapy and transcutaneous electrical nerve stimulation (TENS) on pain intensity, pressure pain threshold (PPT) and conditioned pain modulation (CPM) in patients with primary dysmenorrhea (PD).DesignA randomized, placebo-controlled, double-blind clinical trial.SettingPhysiotherapy Department of the Universidade Cidade de São Paulo, São Paulo (Brazil).InterventionsEighty-eight dysmenorrheic women were randomly allocated into four groups: Thermotherapy + TENS(n = 22), Thermotherapy(n = 22), TENS(n = 22) and Placebo(n = 22). Thermotherapy was applied by microwave diathermy (20 min), and TENS (200 μs, 100 Hz, 30 min), into the lower abdomen both.Main outcome measuresPain intensity was measured using the numeric rating scale (NRS) and the McGill Pain Questionnaire (Br-MPQ). PPT and CPM were recorded from women’s abdominal and lumbar. The evaluation was done in 5 times: baseline, after 20, 50, 110 min and 24 h from intervention.ResultsThere was a significant decrease in the NRS for Thermotherapy + TENS vs. TENS, for Thermotherapy vs. TENS and for Placebo, after 20 min; for Thermotherapy vs. TENS and for Placebo, after 110 min and 24 h. Abdome PPT increased in the Thermotherapy + TENS vs. TENS and Placebo, after 50 min; for Thermotherapy + TENS vs. Placebo and for Thermotherapy vs. Placebo, after 110 min. No changes in lumbar PPT and CPM were observed.ConclusionsThe use of thermotherapy reduced NRS compared to the TENS and Placebo after 20, 110 min and 24 h. Thermotherapy demonstrated an increase in the PPT in the abdomen after 50 and 110 min and decreased the Br-MPQ scores after 110 min in patients with PD.     

Longitudinal and Temporal Associations Between Daily Pain and Sleep Patterns After Major Pediatric Surgery

Approximately 20% of children develop persistent pain after major surgery. Sleep disruption has been implicated as a predictor of children's acute postsurgical pain. However, perioperative sleep patterns have not been longitudinally assessed, and the role of sleep in persistence of postsurgical pain has not been explored. We aimed to examine sleep patterns over 4 months in children having major surgery, and temporal relationships between daily sleep and pain. Sixty children age 10 to 18 (mean = 14.7) years having major surgery completed 7 days of actigraphy sleep monitoring (sleep duration, efficiency), twice daily electronic diaries (sleep quality, pain intensity, medication use), and validated questionnaires at presurgery, 2 weeks, and 4 months postsurgery. Generalized linear models, controlling for age, sex, naps, and medication, showed sleep quality (β [B] = ?.88, P < .001) and efficiency (B = ?1.50, P = .036) were significantly reduced at 2 weeks compared with presurgery, and returned to baseline by 4 months. Poorer night-time sleep quality was significantly associated with greater next day pain intensity (B = ?.15, P = .005). Sleep duration and efficiency were not associated with subsequent pain; daytime pain was not associated with subsequent sleep. Findings suggest sleep quality may be an important target for intervention after surgery in children; research is needed to understand how other sleep parameters may relate to recovery.

The Effect of Fibromyalgia and Widespread Pain on the Clinically Significant Temporomandibular Muscle and Joint Pain Disorders—A Prospective 18-Month Cohort Study

Although most cases of temporomandibular muscle and joint disorders (TMJD) are mild and self-limiting, about 10% of TMJD patients develop severe disorders associated with chronic pain and disability. It has been suggested that fibromyalgia and widespread pain play a significant role in TMJD chronicity. This paper assessed the effects of fibromyalgia and widespread pain on clinically significant TMJD pain (GCPS II-IV). Four hundred eighty-five participants recruited from the Minneapolis/St. Paul area through media advertisements and local dentists received examinations and completed the Graded Chronic Pain Scale (GCPS) at baseline and at 18 months. Baseline widespread pain (OR: 2.53, P = .04) and depression (OR: 5.30, P = .005) were associated with onset of clinically significant pain (GCPS II-IV) within 18 months after baseline. The risk associated with baseline fibromyalgia was moderate, but not significant (OR: 2.74, P = .09). Persistence of clinically significant pain was related to fibromyalgia (OR: 2.48, P = .02) and depression (OR: 2.48, P = .02). These results indicate that these centrally generated pain conditions play a role in the onset and persistence of clinically significant TMJD.     

Comparison of a foam rolling session with active joint motion and without joint motion: A randomized controlled trial

Background

Foam rolling has become a popular form of self-myofascial release or roller massage among health and fitness professionals. Due to this popularity, foam roller devices can be found in many clinical and fitness settings. Despite the popularity, there are still several unknowns regarding foam rolling such the optimal technique. Specifically, there is a lack of research analyzing different foam roll techniques such as combining active joint motion with foam rolling.

Defective Endogenous Pain Modulation in Fibromyalgia: A Meta-Analysis of Temporal Summation and Conditioned Pain Modulation Paradigms

To study the characteristics of temporal summation (TS) and conditioned pain modulation (CPM) in fibromyalgia (FM) patients, we systematically searched Pubmed and EMBASE for studies using TS or CPM comparing FM patients with healthy controls. We computed Hedges' g, risk of bias, sensitivity analysis, and meta-regression tests with 10,000 Monte-Carlo permutations. Twenty-three studies (625 female and 23 male FM patients and 591 female and 81 male healthy controls) were included. The meta-analyses showed an effect size of .53 for TS (P?<?.001; 95% confidence interval = .23–.83), which is a 68% relative difference between patients and controls, and of .57 for CPM (P?<?.001; 95% confidence interval = ?.88 to ?.26), representing a 65% relative difference between the groups. The qualitative analyses revealed large heterogeneity between study protocols. Although studies were of low risk of bias, lack of blinding was substantial. Sensitivity analysis and meta-regression identified type and site of stimulation, age, lab, sample size, and medication control as important sources of between-study variability. We showed a significant alteration of pain modulation mechanisms in FM patients.

Effect of conditioned pain modulation on trigeminal somatosensory function evaluated by quantitative sensory testing

The aim of the study was to systematically investigate the effect of craniofacially evoked conditioned pain modulation on somatosensory function using a quantitative sensory testing (QST) protocol applied to the trigeminal area in healthy humans. Pressure pain evoked by a mechanical compressive device was applied as conditioning stimulus (CS) in the craniofacial region, with a pain intensity of 5 on a visual analogue scale (VAS: 0–10 cm) (painful session) or with VAS score of 0 (control session). A full QST battery of 13 parameters was performed as test stimuli on the dominant-side cheek. The individual QST data from 11 men and 12 women were transformed into z scores, and the QST data and z scores were tested using analyses of variance. Analyses of variance of pressure pain threshold (PPT) data (log-transformed values and z scores) indicated significant session (P ? .003) and time (P < .001) effects with a session–time interaction (P < .001), but no main effect of sex (P ? .053, effect size ? .166). The session–time interaction showed that the PPTs in the painful session were associated with significantly higher log-transformed PPT values and significantly lower z scores compared with the control session at the time point during CS (hypoalgesia) (P < .001). No other QST parameters were significantly modulated by the CS. Sex differences were not detected in this study; a larger sample size may be needed to further explore this possibility. However, the findings indicate that when extensive QST protocols are applied, PPT may be the most sensitive measure to detect endogenous pain inhibitory mechanisms.     

Changes of Hypertonic Saline–Induced Masseter Muscle Pain Characteristics,by an Infusion of the Serotonin Receptor Type 3 Antagonist Granisetron

This study aimed to investigate whether granisetron reduces masseter muscle pain and allodynia induced by hypertonic saline. Fifteen healthy women and 15 age-matched healthy men participated in this randomized, placebo-controlled, double-blinded study. They first received bilateral injections of hypertonic saline into the masseter muscles (internal control). The evoked pain intensity and the pressure-pain threshold (PPT) were recorded during 30 minutes. Granisetron was then injected on one side and placebo (normal saline) on the contralateral side. Two minutes thereafter, the hypertonic saline injections were repeated. Pain and PPT were again recorded. The first injection of hypertonic saline induced pain of similar intensity, duration, and pain area on both sides, but with larger pain area in the women (P = .017). The PPT did not change significantly. The second injection of hypertonic saline induced considerably less pain (62.5%), of shorter duration (44.1%), and of smaller area (77.4%) on the side pretreated with granisetron (P = .005). The PPT was increased on the granisetron side in the men (P = .002). The results of this study show that local injection of a single dose of granisetron attenuates masseter muscle pain induced by hypertonic saline.PerspectiveThis article presents the changes of hypertonic saline–induced masseter muscle pain characteristics by infusion of granisetron. It appears that the pain-inducing effect in this experimental pain model is partly due to activation of 5-HT₃-receptors. Hence, the results indicate that granisetron might offer a new treatment approach for localized myofascial pain.     

Ischemic Pressure vs Postisometric Relaxation for Treatment of Rhomboid Latent Myofascial Trigger Points: A Randomized,Blinded Clinical Trial

ObjectiveThe purpose of this study was to investigate the effects of ischemic pressure (IP) vs postisometric relaxation (PIR) on rhomboid-muscle latent trigger points (LTrPs).MethodsForty-five participants with rhomboid-muscle LTrPs were randomly assigned into 3 groups and received 3 weeks of treatment—group A: IP and traditional treatment (infrared radiation, ultrasonic therapy, and transcutaneous electrical nerve stimulation); group B: PIR and traditional treatment; and group C: traditional treatment. Shoulder pain and disability, neck pain and disability, and pressure pain threshold (PPT) of 3 points on each side were measured before and after treatment.ResultsMultivariate analysis of variance indicated a statistically significant Group × Time interaction (P = .005). The PPT for the right lower point was increased in group A more than in groups B or C. Neck pain was reduced in group B more than in group C. Moreover, shoulder and neck disability were reduced in both groups A and B more than in group C. The PPTs of the left lower and middle points were increased in group B compared with groups A and C. The PPT of the left upper point was increased in group A more than in group C. There were significant changes in all outcomes in the 2 experimental groups (P < .05). No changes were found in the control group except in pain intensity, shoulder disability, and PPT of the left lower point.ConclusionThis study found that IP may be more effective than PIR regarding PPT, but both techniques showed changes in the treatment of rhomboid-muscle LTrPs.     

A psychophysical study of endogenous analgesia: The role of the conditioning pain in the induction and magnitude of conditioned pain modulation

Endogenous analgesia (EA) can be examined experimentally using a conditioned pain modulation (CPM) paradigm. While noxious conditioning stimulation intensities (CSIs) are mainly used, it has not been fully investigated in the same experimental design whether the experienced conditioning pain level affects CPM responses. The principal goal of the present study was to characterize CPM induction and magnitudes evoked by various conditioning pain levels. Furthermore, we explored associations between conditioning pain reports and CPM responses across various CSIs. Thirty healthy, young, right‐handed males were tested with a parallel CPM paradigm. Three different CSIs (hand water‐immersion) induced mild, moderate and intense pain levels, rated 12.41±7.85, 31.57±9.56 and 58.1±11.43, respectively (0–100 numerical pain scale) (P<0.0001). Contact‐heat ‘test‐stimulus’ levels were compared before and during conditioning. Within the group, (i) CPM was induced only by the moderate and intense CSIs (Ps≤0.001); (ii) no difference was demonstrated between the magnitudes of these CPM responses. Regression analysis revealed that CPM induction was independent of the perceived conditioning pain level, but associated with the absolute CSI (P<0.0001). Conditioning pain levels were correlated across all CSIs, as were CPM magnitudes (Ps≤0.01). We conclude that among males, (i) once a CPM response is evoked by a required conditioning pain experience, its magnitude is not further affected by increasing conditioning pain and (ii) CPM magnitudes are inter‐correlated, but unrelated to conditioning pain reports. These observations may suggest that CPM responses represent an intrinsic element of an individual's EA processes, which are not significantly affected by the experienced conditioning pain.     

Experimental pelvic pain facilitates pain provocation tests and causes regional hyperalgesia

The extra-articular sacroiliac joint (SIJ) structure is a potential source for low back and pelvic pain. This study hypothesised that experimental pain induced in a superficial pelvic ligament causes (1) hyperalgesia to pressure, (2) distinct pain referral, and (3) an increased frequency of positive pain provocation tests of the SIJ complex. Thirty healthy subjects (15 females) participated in this study designed as a randomised crossover trial. Pain was induced in the long posterior sacroiliac ligament by injection of hypertonic saline, with the contralateral ligament injected with isotonic saline as control. Pain intensity was assessed on an electronic visual analogue scale (VAS). Pressure pain thresholds (PPTs) and pain provocation tests were assessed on 3 occasions: at baseline, after injection, and when pain had subsided. PPT sites were located bilaterally at the injection site, lateral to spinous processes of S2 and L5, and at the gluteus medius and gastrocnemius muscles. Hypertonic saline caused significantly higher VAS scores and more extended pain referral than isotonic saline (P < 0.001). PPTs at the injection site and lateral to S2 were significantly reduced after hypertonic saline compared with baseline and isotonic saline (P < 0.002). Significantly more subjects had positive pain provocation tests after hypertonic (67% of subjects) compared with isotonic saline (20%; P < 0.001). These data demonstrate that the extra-articular SIJ structure accommodates nociceptors that are capable of inducing pain referral and regional hyperalgesia sensitive to manual pain provocation tests similar to what previously have been found in pelvic girdle pain patients.     

Assessment of Responsiveness to Everyday Non-Noxious Stimuli in Pain-Free Migraineurs With Versus Without Aura

Migraineurs with aura (MWA) express higher interictal response to non-noxious and noxious experimental sensory stimuli compared with migraineurs without aura (MWoA), but whether these differences also prevail in response to everyday non-noxious stimuli is not yet explored. This is a cross-sectional study testing 53 female migraineurs (30 MWA; 23 MWoA) who underwent a wide battery of noxious psychophysical testing at a pain-free phase, and completed a Sensory Responsiveness Questionnaire and pain-related psychological questionnaires. The MWA group showed higher questionnaire-based sensory over-responsiveness (P?=?.030), higher magnitude of pain temporal summation (P?=?.031) as well as higher monthly attack frequency (P?=?.027) compared with the MWoA group. Overall, 45% of migraineurs described abnormal sensory (hyper- or hypo-) responsiveness; its incidence was higher among MWA (19 of 30, 63%) versus MWoA (6 of 23, 27%, P?=?.012), with an odds ratio of 3.58 for MWA. Sensory responsiveness scores were positively correlated with attack frequency (r?=?.361, P?=?.008) and temporal summation magnitude (r?=?.390, P?=?.004), both regardless of migraine type. MWA express higher everyday sensory responsiveness than MWoA, in line with higher response to experimental noxious stimuli. Abnormal scores of sensory responsiveness characterize people with sensory modulation dysfunction, suggesting possible underlying mechanisms overlap, and possibly high incidence of both clinical entities.

Internal validity of inter‐digital web pinching as a model for perceptual diffuse noxious inhibitory controls‐induced hypoalgesia in healthy humans

Hot and ice‐water immersions are commonly used for heterotopic noxious counter‐stimulation (HNCS) in investigations on endogenous pain modulation. However, coincident sympathetic thermoregulatory activity does not allow to differentiate between perceptual hypoalgesia related to baroreflex sensitivity (BRS) or diffuse noxious inhibitory controls (DNIC). The present study analysed the internal validity of another supposedly less confounded tonic pain model (inter‐digital web pinching; IWP) regarding its potential as DNIC trigger. We performed a randomized controlled study in 24 healthy gender‐matched drug‐free volunteers aged 21–54 (median 25) years. The study protocol comprised the assessment of mechanical and thermal perceptual wind‐up before and after an IWP (15N) or hot water immersion trial (HIT; 47.5°C) of 2min duration. Wind‐up was induced either by 10 repetitive (1Hz) contact heat (max. 49°C; 5×5mm thermode) or ballistic impact stimuli (0.5g at 9m/s) on the phalanges of the non‐dominant hand. Cardiovascular activity, pain experience and corrugator muscle activity were continuously monitored. Although both HNCS forms produced a similar pain experience (45% of scale), a more pronounced cardiovascular activity was observable for the HIT (P<0.01). This indicates a higher baroreceptor activity and stronger contamination of painful water immersion by BRS‐related hypoalgesia. Regardless of pain modality, wind‐up was significantly reduced by HNCS, although this was stronger for painful water immersion than for noxious pinching (P<0.01). The HNCS types allow a differentiation between BRS‐related and DNIC‐like hypoalgesia. IWP proved its validity for DNIC induction, being practically non‐confounded by BRS.     

Behavioral Inhibition and Behavioral Activation are Related to Habituation of Nociceptive Flexion Reflex,but Not Pain Ratings

Habituation (ie, decreases in responding) and sensitization (ie, increases in responding) after prolonged or repeated exposures to a fixed stimulus have been identified as important in adaptation to repeated or prolonged noxious stimulation. Determinants of habituation or sensitization are poorly understood, and experimental investigation of habituation of pain ratings have generally relied on pain reports and statistical techniques that average responses across a group of participants. Using a cross-sectional design, the current study used multilevel growth curve analyses to examine changes in the nociceptive flexion reflex (NFR), a spinal nociceptive withdrawal reflex, and pain ratings in response to 12 repeated, constant intensity, noxious electrocutaneous stimuli. Unconditional growth curve models indicated that, on average, participants evidenced habituation of the NFR and sensitization of pain ratings. However, a substantial subgroup of participants exhibited the opposite pattern of change. In conditional models, behavioral inhibition, b = .10, P = .003, and behavioral activation, b = ?.07, P = .07, independently interacted with the growth curve to predict changes in NFR, but not pain ratings, across the 12 stimuli. These findings provide preliminary experimental support for Jensen and colleagues' 2-factor model of pain experience and implicate a role for approach and avoidance motivations in descending modulation of NFR.

Associations Between Pain Appraisals and Pain Outcomes: Meta-Analyses of Laboratory Pain and Chronic Pain Literatures

In this research, meta-analyses were performed to evaluate associations between primary appraisals of pain as a source of threat and/or challenge and responses to 1) noxious laboratory stimuli and 2) chronic noncancer pain. Twenty-two laboratory pain studies comprising 2,031 participants and 59 chronic pain studies based on 9,135 patients were identified for analysis. For laboratory pain, elevated threat appraisals were linked to overall increases in reported pain, reduced pain tolerance, and high levels of passive coping. Method of measuring appraisal as well as type and duration of noxious stimulation moderated some of these associations. Challenge appraisals were related to more pain tolerance and less passive coping but not pain intensity. For chronic pain studies, threat appraisals had positive overall correlations with pain intensity, impairment, affective distress, and passive coping but were negatively related to active coping. The pattern of associations between challenge appraisals and outcomes was largely complementary. Appraisal scale used and gender were consistent moderators of appraisal-outcome relations in chronic pain samples. In sum, appraisals of pain as a source of potential damage or opportunity have robust associations with responses to acute laboratory pain and ongoing chronic pain.PerspectiveMeta-analyses evaluated associations between primary appraisals and responses to laboratory pain and chronic pain. Significant effect sizes for most outcomes suggest that appraisals of pain as a source of threat and challenge have important implications for functioning in response to pain.     

Randomized Controlled Trial of Nurse-Delivered Cognitive-Behavioral Therapy Versus Supportive Psychotherapy Telehealth Interventions for Chronic Back Pain

This study evaluated a nurse-delivered, telehealth intervention of cognitive-behavioral therapy (CBT) versus supportive psychotherapy for chronic back pain. Participants (N?=?61) had chronic back pain (pain “daily”?≥6 months at an intensity of ≥4 of 10 scale) and were randomized to an 8-week, 12-session, CBT or to supportive care (SC) matched for frequency, format, and time, with each treatment delivered by a primary care nurse. The primary outcome was the Roland Morris Disability Questionnaire (RMDQ). Secondary outcomes included the numeric rating scale (NRS) and the Patient Global Impressions Scale (CGI). CBT participants (n?=?30) showed significant improvements on the RMDQ (mean = 11.4 [SD = 5.9] vs 9.4 [SD = 6.1] at baseline and post-treatment, respectively, P?<?.05; d?=?.33), NRS (mean = 4.9 [SD = 2.1] vs 4.0 [SD = 1.9], respectively, P?<?.05; d?=?.45), and on the CGI (39.1% reporting “much improved” or “very much improved”). SC participants (n?=?31) also showed significant improvements on the RMDQ (mean = 11.1 [SD = 5.4] vs 9.1 [SD = 5.2], respectively, P?<?.05; d?=?.38), the NRS, (mean = 5.0 [SD = 1.9] vs 3.8 [SD = 2.1], respectively, P?<?.05; d?=?.60), and 26.7% reporting “much improved” or “very much improved” on the CGI. Between groups comparisons of CBT and SC showed no differences on the study outcomes (Ps > .10). The results suggest that telehealth, nurse-delivered CBT, and SC treatments for chronic back pain can offer significant and relatively comparable benefits.

The correlation between scapulocostal syndrome and masticatory myofascial pain on selected pain and functional parameters- an observational study

ObjectivesAlthough scapulocostal syndrome (SCS) and masticatory myofascial pain (MMP) occur in different regions, the concept of myofascial linkage and neurophysiology may be proven per the connection of the two disorders. Therefore, this study aimed to investigate the correlation between SCS and MMP on selected pain and functional parameters.Method75 participants with SCS participated in the protocol. The diagnosis of SCS was considered by the presence of muscle referred pain in the medial scapular muscles. All participants were measured for pain intensity, pressure pain threshold (PPT), and craniovertebral angle (CV-angle) for pain and functional parameters related to SCS. They were measured for pain intensity, PPT, and mouth distance for the pain and functional parameters related to MMP. The diagnosis of MMP was considered by the presence of muscle tenderness of the masticatory muscle and the decreasing of mouth opening distance. The correlation between SCS and MMP was determined using Pearson's correlation coefficient and Spearman's correlation.ResultsParticipants exhibiting SCS were diagnosed for MMP at 74.67%. The results showed positive correlations in pain intensity and PPT between SCS and MMP (r = 0.367, r = 0.478, p < 0.01), PPT of SCS, and mouth distance amid both pain-free and maximum mouth opening conditions, respectively (r = 0.290, r = 0.282, p < 0.05).ConclusionIn conclusion, SCS and MMP present an association with each other in terms of both selected pain, and functional parameters. Thus, a treatment program for SCS patients should be concerned with the masticatory muscles even if they did not report any pain at the jaw area.     

Experimental muscle pain impairs descending inhibition

In chronic musculoskeletal pain conditions, the balance between supraspinal facilitation and inhibition of pain shifts towards an overall decrease in inhibition. Application of a tonic painful stimulus results in activation of diffuse noxious inhibitory controls (DNIC). The aims of the present experimental human study were (1) to compare DNIC, evoked separately, by hypertonic saline (6%)-induced muscle pain (tibialis anterior) or cold pressor pain; (2) to investigate DNIC evoked by concomitant experimental muscle pain and cold pressor pain, and (3) to analyze for gender differences. Ten males and 10 age matched females participated in two sessions. In the first session unilateral muscle pain or unilateral cold pressor pain were induced separately; in the second session unilateral muscle pain and unilateral cold pressor pain were induced concomitantly. Pressure pain thresholds (PPT) were measured around the knee joint before, during, and after DNIC induction. Cold pressor pain increased PPT in both males and females with greater increases in males. Hypertonic saline-evoked muscle pain significantly increased PPT in males but not in females. When cold pressor and muscle pain were applied concomitantly the PPT increases were smaller when compared to the individual sessions. This study showed for the first time that two concurrent conditioning tonic pain stimuli (muscle pain and cold pressor pain) cause less DNIC compared with either of the conditioning stimuli given alone; and males showed greater DNIC than females. This may explain why patients with chronic musculoskeletal pain have impaired DNIC.     

Sensitization in patients with painful knee osteoarthritis

Pain is the dominant symptom in osteoarthritis (OA) and sensitization may contribute to the pain severity. This study investigated the role of sensitization in patients with painful knee OA by measuring (1) pressure pain thresholds (PPTs); (2) spreading sensitization; (3) temporal summation to repeated pressure pain stimulation; (4) pain responses after intramuscular hypertonic saline; and (5) pressure pain modulation by heterotopic descending noxious inhibitory control (DNIC). Forty-eight patients with different degrees of knee OA and twenty-four age- and sex-matched control subjects participated. The patients were separated into strong/severe (VAS ? 6) and mild/moderate pain (VAS < 6) groups. PPTs were measured from the peripatellar region, tibialis anterior (TA) and extensor carpi radialis longus muscles before, during and after DNIC. Temporal summation to pressure was measured at the most painful site in the peripatellar region and over TA. Patients with severely painful OA pain have significantly lower PPT than controls. For all locations (knee, leg, and arm) significantly negative correlations between VAS and PPT were found (more pain, more sensitization). OA patients showed a significant facilitation of temporal summation from both the knee and TA and had significantly less DNIC as compared with controls. No correlations were found between standard radiological findings and clinical/experimental pain parameters. However, patients with lesions in the lateral tibiofemoral knee compartment had higher pain ratings compared with those with intercondylar and medial lesions. This study highlights the importance of central sensitization as an important manifestation in knee OA.