Which San Jiao point lies 4 cun proximal to SJ-4, in the depression between the radius and the ulna, on the radial side of the extensor digitorum communis muscle?

• A. SJ-7
• B. SJ-8
• C. SJ-9
• D. SJ-5

Answer: (B)

This item tests precise localization along the San Jiao channel on the forearm using distance from SJ-4 and clear anatomical landmarks. Four cun above SJ-4 places you well up the forearm, and the description places the point in the interosseous space between the radius and ulna, on the radial (thumb) side of the extensor digitorum communis tendon. That exact spot is San Jiao point eight.

The forearm map for the San Jiao channel uses the extensor digitorum communis tendon as a key landmark, and moving proximally from SJ-4 along that line, the specified position—between the radius and ulna, on the radial side of the tendon, four cun up from the wrist—corresponds to SJ-8. Other points listed are described by different distances or locations relative to SJ-4 and nearby landmarks, so they don’t match this precise description.