Indications

Sudden loss of voice (aphonia), deafness, lower toothache, eye disorders, forearm and arm soreness with pain, and sore throat.

Precise Location

In the posterior forearm region, 5 cun below the elbow tip (olecranon), at the midpoint between the ulna and radius.

Location Method

Sit upright or lie supine with the arm extended and palm facing down. Measure 5 cun (approximately 7 finger-widths) downward from the elbow tip (olecranon) – the point is in the depression between the ulna and radius on the dorsal forearm, where firm pressure produces a distinct sore and distending sensation.

Massage Method

Massage: Press and knead with the thumb. Press and knead Sidu with the thumb about 200 times, or for 3–5 minutes daily, to treat forearm and arm soreness. Therapeutic actions: Unblocks the meridians and collaterals, opens the orifices and sharpens hearing, clears heat and benefits the throat.

Compatibility

Sudden loss of voice (aphonia): Combine with Yamen (GV-15) and Lianquan (RN-23). Deafness and tinnitus: Combine with Tinggong (SI-19), Yifeng (TE-17), and Zhongzhu (TE-3). Lower toothache: Combine with Jiache (ST-6), Xiaguan (ST-7), and Hegu (LI-4). Forearm and arm soreness: Combine with Quchi (LI-11) and Waiguan (TE-5). Sore throat: Combine with Shaoshang (LU-11) and Hegu (LI-4).

Efficacy & Actions

This point belongs to the Hand Shaoyang Sanjiao Meridian and is the Jing-River point of this meridian. It unblocks the meridians and collaterals, opens the orifices and sharpens hearing, and clears heat and benefits the throat. It is a commonly used key point for treating head, face, and upper limb disorders. First documented in Zhenjiu Jiayijing. "Si" means four directions; "Du" means rivers. Located on the lateral forearm, this point is where Sanjiao Meridian qi flows in four directions like rivers – hence the name Sidu (Four Rivers).