My Favourite Acupuncture Points: Small Intestine 3 (SI3)

Small Intestine 3 (SI3), also known as Houxi, is one of those acupuncture points that can be incredibly useful despite its relatively simple location. It is a point I particularly like using when treating neck and upper back problems, spinal tension and certain musculoskeletal conditions.

SI3 is also the Shu-Stream point of the Small Intestine channel and one of the Eight Extraordinary Vessel confluent points, where it connects with the Du Mai (Governing Vessel).

This combination makes SI3 a particularly interesting point from a TCM perspective.

Where is SI3 located?

SI3 is located on the ulnar side of the hand, just proximal to the head of the fifth metacarpal bone.

It can be found when making a loose fist, where a small depression appears on the ulnar border of the hand, proximal to the fifth metacarpophalangeal joint.

The point is generally easy to locate and is often relatively sensitive when palpated.

TCM actions of SI3

SI3 has several important actions in TCM.

🌿 Benefits the neck and spine

This is probably one of the main reasons I reach for SI3.

The Small Intestine channel travels from the hand through the posterior shoulder and neck and ultimately connects with the spine and Governing Vessel.

SI3 is therefore commonly used for:

- Neck pain and stiffness

- Upper back tension

- Shoulder pain

- Thoracic spine discomfort

- Back pain

- Restricted spinal movement

It can be particularly interesting when treating posterior or lateral neck and upper back presentations.

🌿 Opens the Du Mai

SI3 is the confluent point of the Du Mai (Governing Vessel).

The Du Mai is associated with the posterior aspect of the body and the spinal column, making SI3 particularly relevant for conditions involving the spine, neck and back.

This is one reason SI3 can sometimes have effects that seem disproportionate to its location on the hand.

When combined with BL62, which opens the Yang Qiao Mai, SI3 can be used as part of an Eight Extraordinary Vessel pairing.

🌿 Clears heat

SI3 can also be used to clear heat, particularly from the Small Intestine channel.

This gives the point applications beyond musculoskeletal conditions, although its musculoskeletal actions are probably where I find it most useful clinically.

🌿 Benefits the ears

Because of the pathway and relationships of the Small Intestine channel, SI3 can also be used for certain ear presentations, including tinnitus and ear discomfort.

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SI3 for neck and upper back pain

One of my favourite applications for SI3 is neck pain.

Rather than immediately needling directly into the neck, SI3 provides an excellent distal point that can be used to influence the neck and upper spine.

For example, SI3 can be particularly useful when a client presents with:

Neck stiffness + upper trapezius tension + restricted rotation

I may use SI3 as part of a distal approach, sometimes assessing the client's neck movement before and after needling.

This can be especially interesting when there is an obvious difference in range of movement following stimulation of the point.

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A useful point for the posterior chain

Another reason I like SI3 is its relationship with the posterior aspect of the body.

The Small Intestine channel travels along the ulnar aspect of the arm before moving through the posterior shoulder and scapular region and into the neck.

This makes SI3 a useful point to consider when the presentation involves the:

Hand → arm → shoulder → scapula → neck → spine

Rather than thinking of SI3 as simply a point on the hand, it can be useful to consider the entire channel pathway.

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The Western anatomical perspective

From a Western anatomical perspective, SI3 is located in the soft tissues around the ulnar aspect of the hand, close to structures associated with the fifth metacarpal.

Needling in this region provides stimulation to local sensory nerve endings and mechanoreceptors.

More broadly, acupuncture stimulation activates peripheral afferent nerve fibres, sending sensory information into the central nervous system.

This sensory input may influence:

- Pain modulation

- Muscle activity

- Autonomic nervous system activity

- Central pain processing

- Local and regional blood flow

These mechanisms provide possible physiological explanations for why stimulating a distal point such as SI3 can sometimes influence pain and movement elsewhere in the body.

It is important, however, not to assume that one specific nerve or anatomical structure completely explains the traditional action of an acupuncture point. TCM channel theory and modern neurophysiology describe the body from very different frameworks.

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Why SI3 is one of my favourites

For me, one of the biggest attractions of SI3 is its versatility.

It is a relatively small point with a surprisingly broad clinical application.

I particularly like considering SI3 when treating:

- Neck pain

- Upper back pain

- Shoulder tension

- Scapular pain

- Spinal stiffness

- Posterior-chain presentations

- Some headaches associated with neck tension

- Certain ear-related complaints

It can also be useful when a local area is too sensitive to needle directly.

For example, if someone's neck is extremely irritable, using a distal point such as SI3 can provide a way of beginning treatment without immediately adding more stimulation to the painful region.

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SI3: A small point with a big clinical role

SI3 is a great example of why acupuncture isn't always about putting a needle directly where something hurts.

From a TCM perspective, its status as the Shu-Stream point of the Small Intestine channel and confluent point of the Du Mai gives it an important role in treating the neck, spine and posterior aspect of the body.

From a Western perspective, stimulating SI3 provides sensory input that can influence the nervous system and pain-processing mechanisms.

Whether you're approaching the point through channel theory, the Eight Extraordinary Vessels, distal acupuncture or neurophysiology, SI3 is a point worth having in your clinical toolbox.

Sometimes one of the most useful points for the neck isn't actually in the neck at all.