Study designs of evaluations included in the review
Randomised or quasi-randomised controlled trials were eligible for inclusion in the review.
Specific interventions included in the review
The following types of spinal manipulative therapy were eligible for inclusion: high velocity, low amplitude manipulation; low velocity, small or large amplitude joint mobilisation; manual traction and craniosacral therapy. The trials included in the review assessed manipulation, or a combination of manipulation and mobilisation techniques.
Participants included in the review
Adults with non-specific lower back pain of more than 3 months' median duration were eligible for inclusion. The mean duration of pain for adults included in the trials was 28.1 months.
Outcomes assessed in the review
Trials that reported at least one of the following outcomes were eligible for inclusion: disability, pain, quality of life, adverse events, return to work, global perceived effect, or patient satisfaction with therapy. Pain reduction of at least 20 mm (on a 100-mm visual analogue scale) and disability reduction of at least 30 points (on a 100-point disability scale) were considered clinically worthwhile values.
How were decisions on the relevance of primary studies made?
Two reviewers, who also reviewed selected articles for inclusion, independently screened the search results. Any disagreements were resolved by reference to a third independent reviewer. Where it was unclear if an article met the inclusion criteria, the authors were contacted for further information. When such information was not made available, the reviewers reached a decision by consensus.