 The lumbar facet joints are innervated by the medial branches of posterior primary ramus of the spinal nerve L1-L5. Each of these posterior primary rami divide into medial, intermediate and lateral branches except L5 posterior primary ramus. The medial branches innervate the facet joints and the multifidus muscle. The intermediate branches innervate the muscle longissimus thoracis. The lateral branches innervate the iliocostalis lumborum muscle. The lateral branches of L1, 2 ,3 supply the skin over the lower back. 