Yaóyángguān (M-BW-24) is located approximately 3.5 cun lateral to the lower border of which vertebra?

• A. L3
• B. L5
• C. L4
• D. L2

Answer: (C)

Locating back points uses two reliable references: a vertical vertebral level and a horizontal distance from the spine measured in cun. For Yaoyangguan, find the lower border of a lumbar vertebra and then measure 3.5 cun laterally from the midline to land on the point along the Bladder channel in the lumbar region.

The specified vertical level is the lower border of the fourth lumbar vertebra. This level is chosen because it provides a stable, palpable landmark (the L4 lower border aligns with the iliac crest area and is easy to identify on most people), so the point can be located consistently. Moving to a different vertebral level, such as L2, L3, or L5, would place the point at a different location and would not correspond to Yaoyangguan.

So, Yaoyangguan is located about 3.5 cun lateral to the lower border of L4.