Purpose : Bleeding from the lumbar artery is a potential complication during the transpsoas approach to the lower lumbar intervertebral discs. In this anatomic study, the morphological relationships between the branches of the lumbar artery and the lower intervertebral disc were investigated to assess the risk of injury to the branches of the lumbar segmental arteries. ; Methods : We studied 88 sites (86 lumbar arteries) at the third and fourth lumbar vertebrae bilaterally in 22 formalin-fixed cadavers. The branches of the lumbar artery coursing along the lateral sides of the lower intervertebral disc [muscular branch, anastomotic branch, and branch supplying the spinal nerve and plexus (BSNP)] and the iliolumbar artery running upward over the L4–5 disc were identified. Branches crossing the intervertebral discs vertically were evaluated. ; Results : Muscular branches with a lumen structure longer than 2 cm coursed vertically over the middle third of the intervertebral disc in 3 of 88 sites (3.4 %). Anastomotic branches ran downward in 13 of 88 (14.8 %), and iliolumbar arteries ran upward on the posterior third of the lateral sides of the disc in 2 of 88 (2.3 %). BSNPs ran downward through the posterior third of the disc at 18 of 88 sites (20.5 %). Overall, the arterial branches coursed vertically over the posterior third of the lateral sides of the intervertebral discs in approximately 30 % of subjects. ; Conclusions : Lumbar artery branches coursed vertically over the middle third and the posterior third of the lateral sides of the intervertebral discs in approximately 3 and 30 % of subjects, respectively.