The depression between the two bones of the forearm is like a water channel. In ancient times, Jiang (Yangtze River), Huai (Huaihe River), He (Yellow River), and Ji (Jishui) were called Sidu (TE9), which means that the meridian qi reaches this point and the irrigation is wider.

[Location]

Sidu (TE9) acupoints
(quoted from "Meridians and Acupoints")

• Zhenjiu Jiayi Jing: "Among those who are weak five inches away from the elbow."

[Anatomy]

• Muscles: extensor digiti minimi, extensor digitorum on the radial side, extensor carpi ulnaris on the ulnar side, extensor pollicis longus and abductor pollicis longus on the deep side.
• Nerve: Posterior cutaneous nerve of the forearm, with deep forearm posterior interosseous neuromuscular plexus.
• Vessel: There are posterior interosseous arteries and veins of the forearm in the deep layer.

[Manipulation]

Perpendicular insertion is 0.5~1.5 inches, moxa cone moxibustion is 3~5 inches, moxa stick warm moxibustion is used for 5~15 minutes.

[Efficacy]

Clear ears and clear throat.

• Classical: deafness, toothache, pharyngeal swelling, cheek ulcers, mumps, arm pain.
• Modern: Wrist droop, forearm paralysis, wrist extension weakness, finger cirrhosis, foreign body sensation in the throat, head swelling and pain.

[Recipe]

• Ear burst: Tianyou (TE16), Sidu (TE9).
• headache: Taiyang (EX-HN5), Sidu (TE9).
• Forearm pain and weakness of wrist extension: Quchi (LI11), Sidu (TE9).