The effectiveness of hip interventions in patients with low-back pain: A systematic review and meta-analysis

SYSTEMATIC REVIEW The effectiveness of hip interventions in patients with low-back pain: A systematic review and meta-analysis Luis Ceballos-Laita a, *, Elena Est ebanez-de-Miguel b , Jose Jes us Jim enez-Rejano c , Elena Bueno-Gracia b , Sandra Jim enez-del-Barrio a a Clinical Research Group in Health Sciences of Surgery. Department of Surgery, Ophthalmology, Otorhinolaryngology and Physical Therapy, Faculty of Health Sciences, University of Valladolid, Soria, Spain b Department of Physiatry and Nursery, Faculty of Health Sciences, University of Zaragoza, Zaragoza, Spain c Department of Physical Therapy, University of Sevilla, Sevilla. Spain Received 22 March 2022; received in revised form 8 March 2023; accepted 27 March 2023 Available online 5 April 2023 Abstract Background: Low-back pain (LBP) may be directly or indirectly related to impairments from the hip joint. Objective: To evaluate the effectiveness of hip interventions on pain and disability in patients with LBP in the short-, medium-, and long-term. Methods: PubMed,CochraneLibrary,PEDro,WebofScience, and SCOPUS databases were searched in November 2022. Randomized controlled trials involving hip-targeted interventions compared to specific low back interventions in patients with LBP were selected. The outcomes were pain intensity and disability. The quality of the studies was assessed with the risk of bias tool. GRADE was used to rate the certainty of evidence. Meta-analyses were conducted using random effects models. Results: A total of 2581 studies were screened. Eight were included in the meta-analysis involving 508 patients with LBP. The results provided very low certainty that both hip strengthening and hip stretching improved pain (MD = -0.66; 95% CI -0.86, -0.48; I 2 :0%) (MD = -0.55; 95% CI -1.02, -0.08) and disability (SMD = -0.81; 95% CI -1.53, -0.10; I 2 : 80%) (SMD = -1.03; 95% CI -1.82, -0.25) in the short-term, respectively. No benefits were found in the medium- or long-term. The risk of bias, heterogeneity, and imprecision of the results downgraded the level of evidence. Conclusions: Very low certainty evidence suggest a positive effect of hip strengthening in isolation or combined with specific low back exercise and hip stretching combined with specific low back exercise for decreasing pain intensity and disability in the short-term, in patients with LBP. Systematic review registration number: PROSPERO CRD42022303173 © 2023 Associação Brasileira de Pesquisa e Pós-Graduação em Fisioterapia. Published by Elsevier España, S.L.U. All rights reserved. KEYWORDS Disability evaluation; Hip joint; Low back pain; Meta-analysis; Systematic review * Corresponding author at: Calle Universidad S/N, 42002, Campus Duques de Soria, Soria, Spain. E-mail: [email protected] (L. Ceballos-Laita). Social media: MU_OMPT_UIC (L. Ceballos-Laita) https://doi.org/10.1016/j.bjpt.2023.100502 1413-3555/© 2023 Associação Brasileira de Pesquisa e Pós-Graduação em Fisioterapia. Published by Elsevier España, S.L.U. All rights reserved. Brazilian Journal of Physical Therapy 27 (2023) 100502 Brazilian Journal of Physical Therapy https://www.journals.elsevier.com/brazilian-journal-of-physical-therapy Introduction Low Back Pain (LBP) is one of the major causes of pain and disability in adults and a common reason for seeking medical care. 1,2 LBP is experienced by 80% of the population at least once during their lifetime. 3,4 The prevalence of LBP is gradually increasing and is higher among females in all age groups. 5 LBP can be classified based on symptoms duration in acute, sub-acute, or chronic LBP, 6 or according to diagnosis, in which approximately 90% of patients with LBP are categorized as non-specific LBP, meaning that the etiology is not known. 2 The lumbar spine is interconnected to the pelvis and hips, so LBP may be directly or indirectly related to impairments from adjacent structures. Some studies found that an excessive amount of anterior pelvic tilt is used to compensate a lack of hip extension, and that limited hip extension also alters the motor activation of the lumbar spine. 710 In addition, several authors, concluded that patients with LBP often present hip pain and morning stiffness, 11 a reduction of both passive and active hip rotation range of motion, 1217 and/or hip extensor muscle weakness. 18 Exercise therapy is the most recommended intervention for LBP. But, there is no clear evidence on which type of exercise is more effective, 19 and the effects are small to moderate. Based on the interconnection of the lumbopelvic structures with the hip, interventions targeting the hip or the addition of hip-targeted interventions to specific low back interventions may provide better benefits for patients with LBP. Two systematic reviews and meta-analysis addressed this topic and reported conflicting results about the effectiveness of adding hip interventions to specific low back treatments. 20,21 Since the publication of these reviews, new randomized controlled trials (RCTs) have been published in this field. Therefore, the aim of this systematic review with metaanalysis was to investigate the effectiveness of hip-targeted interventions, in isolation or in combination with LBP interventions, compared to specific low back interventions to improve pain and disability in patients with LBP. Methods Study design The protocol of this systematic review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) with the registration number CRD42022303173. This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement and Cochrane recommendations. 22 Search strategy The bibliographical search was conducted in PubMed (MEDLINE), Physiotherapy Evidence Database (PEDro), Scopus; Cochrane Library, and Web of Science (WOS) from inception to 20 November 2022. The Population, Intervention, Comparison, Outcome, and Study design (PICOS) framework was used to define the search strategy. Medical Subjects Headings (MeSH) were used as the keywords in the search strategy: back pain, low back pain, sciatica, low back ache, mechanical low back pain, hip, hip joint, pain measurement, disability evaluation, and clinical trial. The strategies used for each database are shown in Supplementary material  Table S.1. Scopus database was included as a tool for searching gray literature, and a hand search of the reference list of the included studies was performed. Searches were limited to studies in English, French, and Spanish. Eligibility criteria and study selection The included studies met the PICOS criteria: 1) Population: adults diagnosed with LBP; 2) Intervention: hip-targeted conservative interventions applied in isolation or combined with specific low back interventions; 3) Comparison: specific low back interventions in isolation defined as the use of any physical intervention (manual therapy, massage therapy, exercise therapy, thermotherapy, electrotherapy, or other therapy) that targeted the low back specifically and not the hip joint; 4) Outcomes consisted of pain intensity and disability; 5) Study design: RCTs. Studies were excluded if they: 1) were trials conducted with animals, cadavers, or simulators; 2) included participants with traumatic injuries or after surgical interventions; 3) the intervention was applied to the whole body; 4) the outcome variables reported were not the outcomes of interest or were not measured using a valid and reliable instrument. After results of searches were retrieved, references were exported to Mendeley desktop, and duplicates were removed. Two reviewers independently (LC and SJ) assessed the title and abstract of each reference to determine potential eligibility. The same independent reviewers assessed potential full texts. A third author (EE) resolved the discrepancies between the two reviewers. Three authors of original papers were contacted by e-mail to clarify eligibility criteria. The inter-rater agreement was calculated using the Cohen’s kappa coefficient. 23 Data extraction The two authors independently extracted the data from the identified studies using the standardized process adapted from the Cochrane Collaboration. Extracted information included: 1) characteristics of the study population; 2) aspects of the intervention performed; 3) outcome measures; 4) results; and 5) follow-up period. The third assessor resolved any disagreements. Data were analyzed using a qualitative synthesis and, whenever possible, using a quantitative synthesis (meta-analysis). Risk of bias and certainty of the evidence Two assessors assessed the quality of the studies using the Cochrane Risk of Bias tool. The Cochrane Risk of Bias tool determines the potential bias and the internal validity of the studies and classifies them as “low”,“unclear”,or “high”risk based on 7 criteria. 24 This tool has shown to be reliable for evaluating the quality of studies and assessing risk of bias. Funnel plot asymmetry to assess publication bias in the meta-analyses was not conducted in this study 2 L. Ceballos-Laita, E. Est ebanez-de-Miguel, J.J. Jim enez-Rejano et al. because the meta-analyses presented did not meet the rule of at least 10 trials. The GRADEpro GDTwas used to develop a summary of the findings. This classification categorizes the evidence as “high”,“moderate”,“low”,or“very low”and allows researchers and clinicians to discern the importance of the results. The certainty of evidence for the meta-analysis was downgraded according to the presence of the following: risk of bias (downgraded by one level or two levels if more than 25% or 50% of the participants were from studies with poor or fair methodological quality: lack of allocation concealment, random allocation and/or sample size calculation, participant, and personnel blinding, blinding of outcome assessors), inconsistency of results (downgraded by one level if there was significant heterogeneity regarding outcome measurement or intervention, or if the I 2 value was 50%, and two levels if the I 2 was 75%), 25,26 indirectness of evidence (downgraded by one level if different populations, interventions, or comparators were included), and imprecision (downgraded by one level if fewer than 100 participants were included in the comparison, and two levels when the sample sizes were 30 individuals). 2628 Single randomized trials were considered inconsistent and imprecise and provided “low certainty”evidence. This could be further downgraded to “very low”certainty evidence if there was also a high risk of bias. 24,29 Data synthesis and analysis The quantitative synthesis of the results was conducted according to the outcomes considered: pain intensity and disability. When studies used different tools to assess the same outcome, the authors performed inverse variance methods. Separate analyses were performed for pain intensity and disability. When studies reported pain data on a scale other than 0 to 10 (e.g., 0 to 100) we transformed the data into a 0to10scale. 30 Time points of assessment considered were short-term (or post intervention), medium-term (6 months), and long-term (12 months). Mean, standard deviation (SD), and sample size at each time point were extracted for each group. Outcomes were analyzed based on the post-intervention means and SDs by calculating the mean difference (MD) when studies used the same scale or standardized mean difference (SMD) when studies used different scales, with 95% CIs. Significance was set at a Pvalue <0.05. The minimum clinically important change (MCID) on pain intensity was stated as 1.5. 31 For disability, the between-group effects size was used to classify the effect estimates as small (SMD at least 0.2 but less than 0.5), medium (SMD from 0.5 to less than 0.8), or large (SMD 0.8 or greater). 32 Data were combined for meta-analysis using a minimum of two trials assessed as clinically homogeneous. Trials were considered clinically homogeneous if there was a common intervention and outcome. When a three-arm study was included, the data from the control group were divided. 33 Random-effect meta-analysis was performed when the combination of intervention effects could incorporate an assumption that the studies are not all estimating the same intervention effect. 34 A researcher analysed data using RevMan 5.4 software. Results Literature search and screening Eight studies were included in the qualitative and quantitative synthesis. One study was excluded due to lack of information about the comparison group. 35 The description of the selection process is shown in the PRISMA flowchart diagram (Fig. 1). The agreement between reviewers was calculated by kappa with a value of 0.9. Characteristics of included studies A total of 8 RCTs were included comprising 508 patients with LBP. The sample size ranged from 24 to 80 patients. Most studies included patients with LBP for at least 6 weeks, 36 or 3 months. 3740 All the studies included patients with LBP older than 18. 3643 Concerning the LBP diagnosis, 3 studies included patients with non-specific LBP, 36,38,39 one study included patients with mechanical LBP, 41 and 3 studies did not specify the LBP diagnosis. 40,42,43 The sociodemographic and clinical characteristics of the participants in each study are shown in Table 1. The hip-targeted intervention group (hip-targeted intervention) in each trial consisted of different hip interventions. Seven studies added hip-targeted interventions to specific low back interventions, 3639,4143 and only one applied hip treatment in isolation. 40 Four studies combined hip strengthening with specific low back exercise, 3638,42 one applied hip abductor strengthening in isolation, 40 one study combined hip joint stretching with specific low back exercise, 38 and 3 studies applied hip joint mobilization and strengthening plus specific low back intervention. 39,41,43 Specific low back intervention groups (control) were mainly based on lumbar stabilization exercises in all 8 studies. 3643 Table 1 shows the treatments applied in the hip and low-back groups. Information on the duration of the sessions, the number of sessions per week, and the total number of sessions are presented in the Supplementary material - Table S.2. The sessions duration ranged from 20 to 60 min, 3739,42,43 the most common frequency was 23 sessions per week, 3740,42,43 and most of the studies performed a total number of sessions between 18 and 24. 37,38,40,42 Three studies did not reported the frequency, duration, and/or the total number of sessions. 36,41,43 Outcome measures The outcomes considered in this meta-analysis were pain intensity and disability. Seven studies assessed pain intensity. Five studies used the visual analogue scale (VAS), 3640 and 2 used the numeric pain rating score (NPRS). 41,43 Disability was measured for all the studies. Six studies used the Oswestry Disability Index (ODI), 3638,4143 and 2 used the Roland Morris Questionnaire. 39,40 All the studies assessed the outcome variables at baseline and after the intervention (short-term). 3643 Two studies assessed the medium- and long-term results at 6 months and at 12 months of follow-up, respectively. 39,43 3 Brazilian Journal of Physical Therapy 27 (2023) 100502 Study quality and risk of bias All RCTs included in this review showed a high risk of selection bias and reporting. Most of the studies correctly performed the random sequence generation, but the concealment allocation was only performed in 3. No study blinded the participants or therapist (this item is expected in conservative non-pharmacological interventions). The Cochrane risk-of-bias tool results are shown in Fig. 2. Synthesis of results Pain intensity Pain intensity was measured in 7 studies after the intervention, 3641,43 and in 2 studies at 6 and 12 months of followup. 39,43 Hip strengthening + specific low back exercise versus specific low back Very low certainty evidence showed that hip strengthening plus specific low back exercise provide statistically significant but clinically unimportant improvement in pain intensity compared to specific low back intervention (MD = 0.66; 95% CI 0.86, 0.48; I 2 : 0%; 3 studies, 153 participants) (Fig. 3A). Hip joint stretching + specific low back exercise versus specific low back Very low certainty evidence showed that hip joint stretching plus specific low back exercise provide statistically significant but clinically unimportant improvement in pain intensity compared to specific low back intervention (MD = 0.55; 95% CI 1.02, 0.08; 1 study, 32 participants) (Fig. 3A). Hip abductor strengthening versus specific low back intervention Very low certainty evidence showed that hip abductor strengthening provide statistically significant but clinically unimportant improvement in pain intensity compared to specific low back intervention (MD = 0.93; 95% CI 1.67, 0.19; 1 study, 24 participants) (Fig. 3A). Hip joint mobilization and hip strengthening + specific low back intervention versus specific low back intervention Very low certainty evidence showed that hip joint mobilization and hip strengthening plus specific low back Fig. 1 PRISMA flowchart. 4 L. Ceballos-Laita, E. Est ebanez-de-Miguel, J.J. Jim enez-Rejano et al. Table 1 Sociodemographic and clinical characteristics of the participants. Participants Intervention Outcome (tool) Follow-up Autor (year) N (sex ratio) Mean age (SD) Diagnosis Low-back group Hip group Hip strengthening + specific low back exercise versus specific low back intervention Lee and Kim 2015 68 CG: 50.0 (11.4); 59.38 (17.3) EG: 54.9 (10.6); 61.0 (13.2) CLBP Lumbar stabilization exercises (n= 37) Lumbar stabilization exercises + hip strengthening (n= 31) -Pain (VAS) -Disability (ODI) Kendall et al. 2015 80 (38 M/42 F) CG: 33 (33.4) EG: 41 (37.4) NSLBP Lumbopelvic exercises (n= 40) Lumbopelvic exercises + hip strengthening (n= 40) - Pain (VAS) - Disability (ODI) Jeong et al. 2015 40 (0 M/40 F) CG: 41.2 (6.7) EG: 41.2 (5.5) CLBP Lumbar stabilization exercises (n= 20) Lumbar stabilization exercises + gluteus muscles strengthening (n= 20) -Disability (ODI) Kim and Yim 2020 66 (34 M/32 F) CG: 47.7 (8.5) EG: 47.0 (9.4) NSLBP Lumbar stabilization exercises (n= 10) Lumbar stabilization exercises + hip strengthening (n= 22) -Pain (VAS) -Disability (ODI) Hip joint stretching + specific low back exercise versus specific low back intervention Kim and Yim B 2020 66 (34 M/32 F) CG: 47.7 (8.5) EG: 47.5 (9.7) NSLBP Lumbar stabilization exercises (n= 10) Lumbar stabilization exercises + hip stretching (n= 24) -Pain (VAS) -Disability (ODI) Hip (abductor) strengthening versus specific low back intervention Aboufazeli et al. 2021 24 (0 M/24 F) CG: 39.0 (5.9) EG: 38.8 (5.8) CLBP Lumbar stabilization exercises (n= 12) Hip abductor strengthening (n= 12) -Pain (VAS) -Disability (RMQ) Hip joint mobilization & hip strengthening + specific low back intervention versus specific low back intervention Bade et al. 2017 84 (50 M/34 F) CG: 48.1 (2.4) EG: 44.8 (2.3) MLBP Guideline-oriented low back treatment (n= 39) Guideline-oriented low back treatment + hip strengthening and hip mobilizations (n= 45) -Pain (NPRS) -Disability (ODI) Fukuda et al. 2021 70 (33 M/37 F) CG:35.2 (12.5) EG:40.2 (12.4) CNSLBP Lumbar stabilization exercises + manual therapy (n= 35) Lumbar stabilization exercises + manual therapy + hip strengthening (n= 35) -Pain (VAS) -Disability (RMQ) Medium-term (6 months) Long-term (12 months) Burns et al. 2021 76 (29 M/47 F) CG:40.2 (19.9) EG:39.0 (18.0) LBP Guideline-oriented low back treatment (n= 39) Guideline-oriented low back treatment + tailored hip treatment (manual therapy and strengthening) (n= 37) -Pain (NPRS) -Disability (ODI) Medium-term (6 months) Long-term (12 months) CG, control group; CLBP, chronic low back pain; CNSLBP, chronic non-specific low back pain; EG, experimental group; LBP, low back pain; MLBP, mechanical low back pain; NPRS, numeric pain rating score; NSLBP, non-specific low back pain; ODI, Oswestry Disability Index; RMQ, Roland Morris Questionnaire; SD, standard deviation; VAS, visual analogue scale. 5 Brazilian Journal of Physical Therapy 27 (2023) 100502 intervention provide no better improvement in pain intensity compared to specific low back intervention (MD = 0.15; 95% CI 0.59, 0.30; I 2 : 0%; 3 studies, 230 participants) (Fig. 3A). These studies measured pain intensity in the mediumterm and long-term. 39,43 Very low certainty evidence showed that hip joint mobilization and hip strengthening plus specific low back intervention provide no better improvement in pain intensity compared to specific low back intervention at medium-term (MD: 0.32; 95% CI: 0.96, 0.31; I 2 : 0%; 2 studies; 146 participants) (Fig. 3B), or long-term (MD: 0.10; 95% CI: 0.65, 0.45; I 2 : 0%; 2 studies; 146 participants) (Fig. 3C). Fig. 2 Risk of bias Cochrane tool. 6 L. Ceballos-Laita, E. Est ebanez-de-Miguel, J.J. Jim enez-Rejano et al. Disability Disability was measured in all the studies after the intervention, 3643 and in 2 studies at 6 and 12 months of followup. 39,43 Hip strengthening + specific low back exercise versus specific low back Very low certainty evidence showed that hip strengthening plus specific low back exercise provide a large improvement in disability compared to specific low back intervention (SMD = 0.81; 95% CI 1.53, 0.10; I 2 : 80%; 4 studies, 220 participants) (Fig. 3D). Hip joint stretching + specific low back exercise versus specific low back Very low certainty evidence showed that hip joint stretching plus specific low back exercise provide a large improvement in disability compared to specific low back intervention (SMD = 1.03; 95% CI 1.82, 0.25; 1 study, 32 participants) (Fig. 3D). Hip abductor strengthening versus specific low back intervention Very low certainty evidence showed that hip abductor strengthening provide no improvement in disability Fig. 3B Forest plot of pain intensity for hip-targeted interventions combined with LBP interventions versus specific low back treatment in the medium-term. Fig. 3A Forest plot of pain intensity for hip-targeted interventions in isolation or in combination with LBP interventions versus specific low back treatment in the short-term. Fig. 3C Forest plot of pain intensity for hip-targeted interventions combined with LBP interventions versus specific low back treatment in the long-term. 7 Brazilian Journal of Physical Therapy 27 (2023) 100502 compared to specific low back intervention (SMD = 0.77; 95% CI 1.60, 0.07; 1 study, 24 participants) (Fig. 3D). Hip joint mobilization and hip strengthening + specific low back intervention versus specific low back intervention Very low certainty evidence showed that hip joint mobilization and hip strengthening plus specific low back intervention provide no improvement in disability compared to specific low back intervention (SMD = 0.06; 95% CI 0.30, 0.42; I 2 : 46%; 3 studies, 230 participants) (Fig. 3D). These studies measured disability in the medium-term and long-term. 39,43 Very low certainty evidence showed that hip joint mobilization and hip strengthening plus specific low back intervention provide no improvement in disability compared to specific low back intervention in themediumterm(SMD=0.01; 95% CI; 0.33, 0.31; I 2 : 0%; 2 studies; 146 participants) (Fig. 3E), or long-term (SMD = 0.05; 95% CI; 0.27, 0.38; I 2 : 0%; 2 studies; 146 participants) (Fig. 3F). According to GRADE, the overall certainty of evidence for all comparisons were rated as very low for pain intensity and disability (Table 2). Fig. 3D Forest plot of disability for hip-targeted interventions in isolation or in combination with LBP interventions versus specific low back treatment in the short-term. Fig. 3E Forest plot of disability for hip-targeted interventions combined with LBP interventions versus specific low back treatment in the medium-term. Fig. 3F Forest plot of disability for hip-targeted interventions combined with LBP interventions versus specific low back treatment in the long-term. 8 L. Ceballos-Laita, E. Est ebanez-de-Miguel, J.J. Jim enez-Rejano et al. Table 2 Summary of evidence of the results according to their certainty and their importance using the GRADE tool. Certainty assessment Nof patients Effect Certainty Nof studies Study design Risk of bias Inconsistency Indirectness Imprecision Others [hip-targeted group] [Control group] Absolute (95% CI) Pain intensity (short-term) Hip strengthening + specific low back exercise versus specific low back 3 RCTs Very serious a Serious c Not serious Serious d None 93 87 MD 0.66 less (0.86 less to 0.46 less) ⨁^ x^ x^ x Very Low Pain intensity (post-intervention) hip joint stretching + specific low back exercise versus specific low back intervention 1 RCTs Very serious a Very serious d None 24 10 MD 0.55 less (1.02 less to 0.08 higher) ⨁^ x^ x^ x Very Low Pain intensity (post-intervention) hip abductor strengthening versus specific low back intervention 1 RCTs Very serious a Very serious d None 12 12 MD 0.93 less (1.67 less to 0.19 higher) ⨁^ x^ x^ x Very Low Pain intensity (post-intervention) hip joint mobilization & hip strengthening + specific low back intervention versus specific low back intervention 3 RCTs Very serious a Serious b Not serious Not serious d None 117 113 MD 0.15 less (0.59 less to 0.3 higher) ⨁^ x^ x^ x Very Low Pain intensity (6 months follow-up) hip joint mobilization & hip strengthening + specific low back intervention versus specific low back intervention 2 RCTs Serious a Serious b Not serious Serious d None 72 74 MD 0.32 less (0.96 less to 0.31 higher) ⨁^ x^ x^ x Very Low Pain intensity (12 months follow-up) hip joint mobilization & hip strengthening + specific low back intervention versus specific low back intervention 2 RCTs Serious a Serious b Not serious Serious d None 72 74 MD 0.10 less (0.65 less to 0.45 higher) ⨁^ x^ x^ x Very Low Disability (post-intervention) Hip strengthening + specific low back exercise versus specific low back intervention 4 RCTs Very serious a Serious c Not serious Not Serious None 113 107 SMD 0.81 less (1.53 less to 0.10 less) ⨁^ x^ x^ x Very Low Disability (post-intervention) hip joint stretching + specific low back exercise versus specific low back intervention 1 RCTs Very serious a Very serious d None 24 10 SMD 1.03 less (1.82 less to 0.25 less) ⨁^ x^ x^ x Very Low Disability (post-intervention) hip abductor strengthening versus specific low back intervention 1 RCTs Very serious a Very serious d None 12 12 SMD 0.77 less (1.6 less to 0.07 less) ⨁^ x^ x^ x Very Low Disability (post-intervention) hip joint mobilization & hip strengthening + specific low back intervention versus specific low back intervention 3 RCTs Very serious a Serious b Not serious Not serious d None 117 113 SMD 0.06 less (0.30 less a 0.42 higher) ⨁^ x^ x^ x Very Low Disability (6 months follow-up) hip joint mobilization & hip strengthening + specific low back intervention versus specific low back intervention 2 RCTs Serious a Serious b Not serious Serious d None 72 74 SMD 0.01 less (0.33 less a 0.31 higher) ⨁^ x^ x^ x Very Low Disability (12 months follow-up) hip joint mobilization & hip strengthening + specific low back intervention versus specific low back intervention 2 RCTs Serious a Serious b Not serious Serious d None 72 74 SMD 0.05 higher. (0.38 higher to 0.27 less) ⨁^ x^ x^ x Very Low CI, confidence interval; MD, mean difference; RCTs, randomized controlled trial; SMD, standardized mean difference. Explanations:. a. More than 25% of the participants were from studies with poor or fair methodological quality, considering these aspects: Lack of allocation concealment, random allocation and/or sample size calculation, participant and personnel blinding, blinding of outcome assessors. b. Significant heterogeneity regarding outcome measurement or intervention, or if the I 2 value was 50%. c. Significant heterogeneity regarding outcome measurement or intervention, or if the I 2 value was 75%. d. Fewer than 100 participants were included in the comparison or single randomized controlled trials included. High: We are very confident that the true effect is close to the estimate of the effect. Moderate: We are moderately confidence in the effect estimate. The true effect is close to the estimate of the effect, but the result can be different. Low: Confidence in the effect estimate is limited, the true effect can be substantially different from the estimate of the effect. Very Low: There is little confidence in the effect estimate, the true effect is likely to be substantially different from the estimate effect. 9 Brazilian Journal of Physical Therapy 27 (2023) 100502