• T9 medial branch → T9–10 & T10–11 facets

• T10 medial branch → T10–11 & T11–12 facets

• T11 medial branch → T11–12 & T12–L1 facets

• T12 medial branch → T12–L1 & L1–L2 facets

• L1 medial branch → L1–2 & L2–3 facets

• L2 medial branch → L2–3 & L3–4 facets

• L3 medial branch → L3–4 & L4–5 facets

• L4 medial branch → L4–5 & L5–S1 facets

• L5 dorsal ramus → L5–S1 facet (via branch to sacral ala/SI capsule)

📚 Reference:  Bogduk N, Wilson AS, Tynan W. The human lumbar dorsal rami. J Anat. 1982;134(Pt 2):383–397.
Bogduk N. Clinical Anatomy of the Lumbar Spine and Sacrum, 5th ed. Churchill Livingstone Elsevier, 2012.

• T11–12 facet → innervated by T10 and T11 medial branches

• T12–L1 facet → innervated by T11 and T12 medial branches
  
  

🩺 Key rule: Each thoracic or lumbar facet joint receives dual innervation, from the medial branch at its own level and the level above.