During lumbar puncture, how is the patient commonly positioned?

• A. On the left side in the fetal position
• B. On back with legs extended
• C. Sitting upright
• D. Standing

Answer: (A)

Maximal bending of the spine is what makes a lumbar puncture easier. When the back is flexed, the interlaminar spaces between the lumbar vertebrae widen, giving better access to the subarachnoid space and reducing the chance of hitting bone or painful nerve structures. The common setup is a lateral decubitus or “fetal” position: the patient lies on one side with the knees drawn toward the chest and the spine in as much flexion as possible. This posture brings the L3–L4 or L4–L5 interspaces into easy reach and stabilizes the patient for a precise needle entry. The left side is often used by convention, but the crucial factor is the pronounced spinal flexion to access the CSF. Other positions, like lying flat with legs extended or sitting upright, don’t provide the same level of flexion and can make the procedure more difficult.