low back pain ( lbp ) is the most common and costly neuromusculoskeletal dysfunction in many countries . nonspecific lbp refers to any type of back pain in the lumbar region that is not related to serious pathology and/or does not have a specific cause . the underlying cause of specific lbp is structural problems or obvious pathologic conditions such as disc herniation ; disk herniation is due for 13% of lbps , and it is the most common cause of radiating lbp in subjects under 60 years of age . radiating lbp is the pain radiating from the low back into the lower extremity and/or foot along the sensory distribution of the affected spinal nerve root . this pain may be due to compression of inflamed spinal nerves within the spinal canal or release of biochemical mediators from the nucleus pulposis . myofascial pain syndrome , characterized by the presence of myofascial trigger points ( mtps ) , may also lead to numbness and referred pain , which can mimic radicular pain . an mtp is a hyperirritable spot within a taut band of skeletal muscle , which is painful on compression . trigger points may produce referral pain , secondary hyperalgesia , motor dysfunction , and autonomic phenomena . prolonged contractions of the paraspinal muscles , especially the multifidus , may result in radiculopathy with radicular pain due to narrowing of the disk space and intervertebral foramina . dry needling ( dn ) is a minimally invasive procedure during which a solid filament needle is inserted into an mtp . as a management for myofascial pain however , because of invasive nature of dn , it raises the potential for procedural side effects . uncommon adverse effects included strong pain during needling , vegetative symptoms , nerve irritation , and injury . the above mentioned adverse effects may be avoided by clinicians who had better anatomical knowledge and critically concern hygiene . the first study regarding the effect of dn on lbp was performed in 1980 , where 56 male patients completed 8 weeks standard physical therapy and exercise without any progress ( according to subjects ' reports ) before enrolling in a randomized control trial ( rct ) . the patients were divided into two groups , including a group treated by standard physical therapy and a group treated by standard physical therapy plus dn . the improvement of experimental group was significantly better than control group in terms of pain intensity and functional disability . although this approach was effective , mtps do not always overlap with the muscle motor point ; therefore , dn should not be restricted only to muscle motor points . according to a cochrane systematic review in 2005 , dn may be a useful adjunct to other therapeutic interventions in the management of chronic lbp ; thus , several research studies have investigated the effect of dn on non - specific lbp . however , the effect of dn in subjects with specific lbp has not been studied yet . the current study aims to compare the pain and function in subjects with discogenic radiating lbp following the standard conservative approach with or without dn . the main hypothesis was that supplementary dn may increase the effect of the standard conservative intervention in patients with discogenic lbp ( dlbp ) . the study was performed in a physical therapy clinic related to isfahan university of medical sciences and approved by the research ethics committee of isfahan university of medical sciences ( december 2013 ) . all participants completed an informed consent form , after receiving information on dn treatment method and the research procedure . the target population includes the subjects with radiating dlbp . in accordance with the study by edwards and knowles , the sample size was estimated 58 ( n = 29 for each group ) with  = 0.05 ,  = 0.08 and  = 0.75 and  = 1 using equation 1 . all patients with discogenic radicular lbp were assessed at baseline for eligibility criteria by blinded registered physiotherapist that was blinded in terms of the study protocol and study groups . the inclusion criteria were age between 20 and 50 years and radiating pain into one or both legs . following participants were excluded from the study : the participants with any coagulation disorder , the participants receiving anticoagulant therapy for any reason due to a potentially increased risk of hematoma following needling , and the participants with any psychological disorder due to the potential unreliable pain reporting , the subjects suffering from needle phobia , any tumor or infection in the lumbar region , acute or chronic radiating lbp resulting from fracture or instability , and the patients with a contraindications to dn . using coin toss , the same equal number of participants were randomly assigned into control and intervention groups by a hospital staff that was blind to the study protocol . control group received standard physical therapy , and experimental group received standard physical therapy plus dn . the subject s attrition is presented in figure 1 . the consort 2010 diagram for attrition of subjects in the study participants were assessed at baseline ( during the first intervention session ) , in the last intervention session , and finally , 2 months after the last intervention session by a blinded physiotherapist . the primary outcome measure , pain intensity , was rated between 0 ( no pain ) to 10 ( maximum pain ) on visual analog scale ( vas ) which is a reliable and valid measure to evaluate pain intensity in lbp subject . regarding the secondary outcome measure , disability , the persian version of the oswestry functional disability questionnaire ( odq ) was used to measure the self - perceived level of functional disability resulted from discogenic radicular lbp . the oswestry questionnaire included 10 items to assess how lbp affects the subjects ' ability to manage their daily activity . the scores of all items were added up to obtain a possible score of 50 , which was then doubled and expressed as a percentage . if an item was not answered , it was excluded from the total potential score and the total percentage was calculated according to the remaining items . patients in both groups received standard physical therapy for 10 sessions every other day , including application of a thermal modality , transcutaneous electrical nerve stimulator ( acupuncture like : frequency = 14 hz , duration = 250 ms , time = 20 min ) , ultrasound ( frequency = 1 mhz , pulsed , intensity = 1 w / cm , time = 1 min/1 cm ) , and exercise therapy ( mckenzie program and stabilizing exercise ) . participants in the experimental group received five sessions of dn at the end of the second , forth , sixth , eighth , and tenth sessions . based on the estimated depth of targeted mtps , 36 cm solid filament needles ( energy needles , wuxi jiajian medical instrument co. , ltd , wuxi , jiangsu , china ) were selected . the needles were inserted directly into mtps or into a taut band by a physiotherapist experienced in palpation and treatment of mtps . the accuracy of the needle insertion sites was confirmed through pain reproduction or observing local twitch response . all needling was performed by the same blinded therapist for all mtps and all participants . according to the presence of mtps , paraspinals ( iliocostalis , longissimus ) , multifidus , quadratus lumborum , gluteus maximus , gluteus medius , gluteus minimus , piriformis , psoas major , hamstrings ( semimembranosus , semitendinosus , biceps femoris ) , and the gastrocnemius were needled . dn was continued for each muscle as long as the subject reported mtp pain , in order words , dn sessions were canceled as soon as the subjects did not report mtp pain any more . since vas data were not normally distributed , they were analyzed by the nonparametric mann odq data were analyzed through parametric independent t - tests to measure the between group differences , respectively . a 3  2 mixed model analysis of variance was used to calculate the change in pain intensity and disability . to control the effect of age and gender on the final pain and disability score , since vas data were not normally distributed , they were analyzed by the nonparametric mann odq data were analyzed through parametric independent t - tests to measure the between group differences , respectively . a 3  2 mixed model analysis of variance was used to calculate the change in pain intensity and disability . to control the effect of age and gender on the final pain and disability score , . demographic characteristics of study groups statistical power was 0.8 for all the statistical tests administered in the study . the baseline pain intensity and disability scores were same in the surveyed groups ( p > 0.05 ) . following intervention , pain intensity decreased significantly in both intervention ( p < 0.001 ) and control groups ( p < 0.001 ) and the change continued during follow - up period ( p < 0.001 for both ) [ figure 2 ] . comparing pain intensity among surveyed groups before , after , and 2 months after intervention . the standard deviations are presented as error bars the same pattern was observed in the oswestry disability score ( p < 0.001 ) [ figure 3 ] . a comparison of pain intensity among surveyed groups before , after , and 2 months after interventions . the standard deviations are presented as error bars however , the decrease in pain intensity ( p = 0.006 ) and disability score ( p = 0.002 ) were significantly more in the experimental group and at the follow - up phase [ figure 4 ] . comparison of disability score between study groups before , after , and 2 months after interventions . asterisk represents significant difference (  = 0.05 ) there was a significant effect for the measurement time ( f [ 2 , 57 ] = 80.36 , p < 0.001 , wilks ' lambdatime = 0.26 , multivariate partial eta squared = 0.75 ) . interaction between time and group was also significant ( f [ 2 , 57 ] = 6.22 , p = 0.004 , wilks ' lambdatime  group = 0.82 , multivariate partial  = 0.19 ) . a bivariate general linear model ( glm ) was also developed for adjusting the effect of the intervention type on pain and disability scores by age and gender [ table 2 ] . the model revealed that age and gender had no significant impact on pain and disability scores in surveyed samples . bivariate general linear model adjusting the effect of the intervention type on pain and disability scores by age and gender in control group , itt were 6.87.5% for vas scores while they were 3.34.5% for disability scores 19.4% of the participants in control group and 14.7% of subjects in experimental group left the study due to unwillingness to continue the program , sickness , or moving house . the present single - blind randomized clinical trial was used to measure the effect of dn on pain intensity and functional disability in subjects with discogenic radiating lbp . the findings of the study confirm the hypothesis stating that dn improves pain and disability parameters in subjects treated with standard conservative physical therapy . although both intervention strategies improved pain and disability significantly , and this improvement lasted 2 months following the active intervention , it seems that adding dn to the intervention procedure increases the impact of standard intervention considerably . although several studies have examined the efficacy of dn for chronic lbp , but the author found no study on the effect of dn on specific lbp including dlbp . the findings of the study are consistent with previous works on nonspecific lbp in term of improvement in pain and functional disability . however , because of the substantial variation in lbp pathogenesis , our results are not comparable to previous works . for example in a study by gunn et al . , subjects with chronic lbp were enrolled among whom traditional medical , rehabilitative , or surgical interventions were not successful . since muscle mtps are highly susceptible to become activated in subjects with lumbar disk herniation , inactivating mtps may reduce the symptoms significantly . our findings were consistent with the results of a recent study , where several parallel modalities were administered for the treatment of mtps . several previous studies indicate that dn is an effective method for subjects with chronic lbp , although none of them has surveyed the effects of dn to relieve radiating pain in subjects with dlbp . gunn hypothesized that mtps in the multifidus muscles may result in long - term contractures with increased pressure on connective tissues surrounding the spinal cord as well as compression and irritation of the nerve roots . nerve root compression may produce radiating pain and may also contribute to the development of mtps in corresponding myotomes through a vicious cycle . it releases analgesic endorphins , increases blood flow , and improves chemical environment in the immediate vicinity of the active mtps . on the other hand , damage to the intervertebral disc increases the secretion of chemical inflammatory mediators such as phospholipase a2 and cytokinase from the nucleus pulposis , which induces nerve root inflammation and can contribute to the radiating pain commonly experienced in this kind of lbp . the study demonstrated that measurement time critically affects the impact of dn on standard physical therapy improvement . in addition , the present results imply that the radiating pain in dlbp may not be only due to a compression - induced irritation of the nerve roots , but it may also be due to the activation of mtps in the natural course of the disorder . the muscles needled in the study were those with a high prevalence of active mtps in dlbp and were the same muscles affected by extension and extension rotation impairments in sahrmann approach . the muscles selected for dn in this study were practically important in managing dlbp : the quadratus lumborum muscle has an important role in spinal stability and its mtps may result in lbp ; the paraspinal muscles , including the iliocostalis and longissimus , are primary lumbar extensors which are prone to tightness and mtp activation in dlbps ; the pattern of referral pain due to gluteals ' mtps mimics that in dlbps since they are prime movers when standing from bending position . the psoas muscle contributes to lumbar lateral flexion , hip flexion , and stabilizing lumbar spine through producing compressive force . it is also involved in mechanical dysfunction of the lumbar spine and lbp due to its extensive spinal column attachments . it seems that management of psoas mtps may relieve pain significantly in the subjects with lbp . conversely , piriformis muscle is the most commonly involved muscle in lbp that acts as one of the primary sources of sciatica and lbp . this muscle fills the greater sciatic foramen with the sciatic nerve passing deep inside it thus ; piriformis tightness or spasm may resemble the symptoms of dlbp . lucas et al . revealed that muscle activation patterns for shoulder abduction in subjects with latent mtps were different from the patterns observed in healthy subjects . besides , hodges believes that the pain may change the mechanical behavior and movement patterns to protect subjects from more pain and potential damages . considering mtps as a source of persistent activation of muscle nociceptors combined with hodge s claims , dn may alter movement and activation patterns in paraspinals , and other muscles by deactivating mtps . therefore , the pathological movement disorders would gradually fade and be replaced by new patterns . itt analysis revealed that there was no significant itt in both groups so that the observed changes may be the net effect of the intervention . this study has some limitations ; we needled various muscles at the same time that inhibits us to determine whether certain muscles are more relevant than others . future studies may improve our understanding of the muscle involvement in dlbp through needling specific muscles . the follow - up period was relatively short to minimize subjects ' attrition . in future studies , longer follow - up along with periodical re - assessments are recommended to examine long - term effects of dn and providing a better insight of pain and symptom patterns . the results of the clinical trial suggest that both intervention strategies significantly improved pain and disability immediately following the intervention while the improvement continued within 2 months after the last active intervention . the supplementary dn application enhanced the effect of the standard intervention considerably . the study was funded and ethically approved by isfahan university of medical sciences as part of a physical therapy master s thesis ( registration code : 393082 ) . the sponsor has no role in data collection , data analysis , and drafting the manuscript . the study was funded and ethically approved by isfahan university of medical sciences as part of a physical therapy master s thesis ( registration code : 393082 ) . the sponsor has no role in data collection , data analysis , and drafting the manuscript . all the authors contributed in the conception of the work , design of the work , data analysis , data interpretation , and drafting the work . consequently , all the authors are accountable for all aspects of the work to ensure that accuracy and integrity of all parts of the work are appropriately investigated and resolved .