Posterior view of lumbar spine showing location of medial branches (mb) of dorsal rami, which innervate lumbar facet joints (a). Needle position for L3 and L4 medial branch. Blocks shown on left half of diagram would be used to anesthetize L4-5 facet joint. Right half of diagram shows L3-4, L4-5, and L5-S1 intraarticular facet joint injection positions. SEETECHNIQUE 39.7.