Lower back pain in regarded as the main cause of disability in the world, which has a significant socio-economic impact. Deep dry needling is effective in handling such pain and is one of the techniques of choice by physiotherapists. In this area, the use of ultrasound provides information of interest such as length, thickness, diameter, cross-sectional area or muscle volume, among others.~Objective: Finding out if tissue changes (thickness, histogram and shrinkage rate) that occur in the lumbar multifidus after deep dry needling are related to changes in patient's pain and disability.~It's a double-blind randomized clinical trial in parallel groups. Patients will be randomly divided into 2 groups. One of them will receive dry needling and the other dry needling placebo. The initial, post-needling and a week after evaluations will be performed by a blinded to the intervention therapist.
Finding out if tissue changes (thickness, histogram and shrinkage rate) that occur in the lumbar multifidus after deep dry needling are related to changes in patient's pain and disability.