Abstract: There were 12 randomised controlled trials with 14 comparisons included in the review, with a total sample of 500 participants across all comparisons. Included studies were typically very small (n = 20 to 72), all except one were assessed as being at high risk of bias, and all reported short-term outcomes. For the purposes of pooling, studies were divided into seven clinically homogenous comparisons according to the patient population (acute or chronic LBP) and the nature of the control intervention. Most of the comparisons (five out of seven) included only one study, one comparison had two studies, and one comparison included seven studies. The meta-analyses provided low-quality evidence that MET provided no additional benefit when added to other therapies on the outcomes of chronic pain and disability in the short-term (weighted mean difference (WMD) for pain 0.00, 95% CI -2.97 to 2.98 on a 100-point scale; standardised mean difference (SMD) for disability -0.18, 95% CI -0.43 to 0.08, 7 studies, 232 participants). There was low-quality evidence that MET produced no clinically relevant differences in pain compared to sham MET (mean difference (MD) 14.20, 95% CI -10.14 to 38.54, 1 study, 20 participants). For the comparison of MET to other conservative therapies for acute non-specific LBP, there was very low-quality evidence of no clinically relevant difference for the outcomes of pain (MD -10.72, 95% CI -32.57 to 11.13, 2 studies, 88 participants) and functional status (MD 0.87, 95% CI -6.31 to 8.05, 1 study, 60 participants). For the comparison of MET to other conservative therapies for chronic non-specific LBP, there was low-quality evidence of no clinically relevant difference for the outcomes of pain (MD -9.70, 95% CI -20.20 to 0.80, 1 study, 30 participants) and functional status (MD -4.10, 95% CI -9.53 to 1.33, 1 study, 30 participants). There was low-quality evidence of no clinically relevant difference for the addition of MET to other interventions for acute non-specific LBP for the outcome of pain (MD -3, 95% CI -11.37 to 5.37, 1 study, 40 participants) and low-quality evidence of an effect in favour of MET for functional status (MD -17.6, 95% CI -27.05 to -8.15, 1 study, 40 participants). For chronic non-specific LBP, there was low-quality evidence of an effect in favour of MET for the addition of MET to other interventions for the outcomes of pain (MD -34.1, 95% CI -38.43 to -29.77, 1 study, 30 participants) and functional status (MD -22, 95% CI -27.41 to -16.59, 1 study, 30 participants). Lastly, there was low-quality evidence of no difference for the addition of MET to another manual intervention compared to the same intervention with other conservative therapies for the outcomes of pain (MD 5.20, 95% CI -3.03 to 13.43, 1 study, 20 participants) and functional status (MD 6.0, 95% CI -0.49 to 12.49, 1 study, 20 participants). No study reported on our other primary outcome of general well-being. Seven studies reported that no adverse events were observed, whereas the other five studies did not report any information on adverse events. The quality of research related to testing the effectiveness of MET is poor. Studies are generally small and at high risk of bias due to methodological deficiencies. Studies conducted to date generally provide low-quality evidence that MET is not effective for patients with LBP. There is not sufficient evidence to reliably determine whether MET is likely to be effective in practice. Large, methodologically-sound studies are necessary to investigate this question.

Plain-language summary: The people in these studies ranged in age from 18 to 65 years and had pain ranging in severity from mild to substantial. They usually had about five sessions of MET, or the comparison treatment(s), over a period of about 10 days. The review authors aimed to determine if MET helped to relieve pain or increase a person's ability to do normal activities of daily living, or both. Background Low-back pain (LBP) is a common symptom from adolescence into old age. About 50% of the general population experiences back pain over the course of a year and up to 80% of people report LBP over the course of their lifetimes. The vast majority of people have acute (short-term) back pain and recover within a few weeks, with or without treatment. Longer lasting LBP, subacute (for 6 to 12 weeks) and chronic (> 12 weeks) pain, generally has less favourable outcomes. A small proportion of people with acute LBP go on to have chronic disabling LBP, which can interfere with every aspect of normal living, cause significant pain and suffering, and create huge costs in terms of medical care, work disability, and workers’ compensation claims. There are many therapies claimed to be useful for the treatment of LBP. Most of these treatments have not been well investigated or have been found to have modest effects in terms of pain relief and improving disability. For many people with LBP, however, even modestly effective treatments can help in coping with symptoms and returning to normal living. It is therefore useful to explore the effectiveness of treatments that may assist people with LBP, particularly those treatments such as MET which are non-invasive and are likely to be safe and inexpensive. Study characteristics The Cochrane Collaboration researchers looked for studies (randomised controlled trials) published through to May and June 2014. They included studies where MET was delivered by osteopathic physicians, chiropractors, or physical therapists. Twelve randomised controlled trials were found that included a total of 500 patients. All patients in these studies had 'non-specific LBP', meaning that there was no identifiable cause for their back symptoms. After looking at the evidence, The Cochrane Collaboration review authors included four types of comparison treatments, each divided into acute and chronic pain: •MET plus any intervention versus that same intervention alone; •MET versus no treatment; •MET versus sham MET; •MET versus all other therapies. Key results The review authors could not find adequate evidence to make any definitive judgements about the safety or effectiveness of MET. Studies were generally too small and had a high risk of bias, producing unreliable answers about this therapy. There is a need for larger, high-quality studies to determine the effectiveness and safety of MET. At present there is no convincing evidence that MET is effective as a stand-alone therapy or improves the effectiveness as an accompaniment to other therapies. Quality of the evidence The quality of the evidence was poor. The available studies were small and reported only short term outcomes. Most studies were determined to have a high risk of bias because of the way they were designed and conducted.