The axillary pain that no one can explain

Pain in the axilla and inner arm is a symptom that immediately generates concern in the patient — and for understandable reasons. In women, the first association is with breast pathology. In men and women, axillary pain with radiation to the arm raises suspicion of a cardiac problem. After normal breast, cardiac, and imaging tests, the patient remains with the pain and without a diagnosis.

Two muscular structures are responsible for most of these cases: the serratus anterior and the subscapularis. These muscles, located on the lateral chest wall and the anterior side of the scapula respectively, have referred-pain patterns that converge on the axilla and the medial side of the arm. Trigger points in these structures are extremely common in people who work with the arms elevated, practice throwing sports, or maintain a posture with protracted shoulders. Dry needling of these muscles, when performed by a physician with anatomic mastery, frequently resolves the pain that multiple tests could not explain.

Serratus anterior and subscapularis — anatomy of axillary pain

  1. Serratus anterior — the muscle of the lateral wall

    The serratus anterior originates from the first 8–9 ribs and inserts on the medial border of the scapula. Its trigger points, located on the lateral chest wall (along the midaxillary line), refer pain to the lateral chest wall, posterior axilla, and, crucially, to the medial side of the arm down to the 4th and 5th fingers. This pattern mimics C8-T1 radiculopathy.

  2. Subscapularis — the hidden muscle of the scapula

    The subscapularis occupies the subscapular fossa (anterior surface of the scapula). Its trigger points refer deep pain to the posterior axilla, posterior shoulder, and dorsal wrist. Because it lies between the scapula and the chest wall, the subscapularis is difficult to palpate and frequently neglected — but it is one of the most common causes of unexplained chronic axillary pain.

  3. Convergence of referred-pain patterns

    When serratus anterior and subscapularis are simultaneously affected — a common situation in scapular dysfunction — the referred-pain patterns overlap on the axilla and medial arm, creating diffuse pain that does not follow dermatomes, does not respect nerve territory, and confuses conventional neurologic investigation.

  4. Needling and scapulothoracic restoration

    Dry needling of the serratus anterior is performed with the patient in lateral decubitus, with the needle inserted tangentially to the chest wall — a technique that minimizes the risk of pneumothorax. The subscapularis can be needled through the axillary border of the scapula with partial arm abduction. Deactivation of these trigger points restores scapulothoracic biomechanics and eliminates the referred pain.

Data on myofascial axillary pain

Relevant proportion
OF MYOFASCIAL AXILLARY PAIN
clinical series suggest that a significant share of chronic axillary pains without a defined diagnosis have myofascial origin — trigger points in the serratus anterior and/or subscapularis as the main or contributing cause
3–5
SPECIALISTS CONSULTED
is the average before the diagnosis of myofascial axillary pain — including breast specialist, cardiologist, neurologist, and orthopedic surgeon
Improvement
WITH NEEDLING
in the myofascial literature, patients with trigger points in the serratus anterior and subscapularis frequently respond well to dry needling in few sessions — magnitude variable across studies
Frequent
SCAPULAR DYSKINESIS
patients with myofascial axillary pain commonly present associated scapulothoracic dysfunction — scapular dyskinesis that perpetuates trigger points

Recognizing myofascial axillary pain

Critérios clínicos
08 itens

Trigger points in the serratus anterior and subscapularis — typical pattern

  1. 01

    Pain in the axilla and medial side of the arm without a breast, cardiac, or neurologic cause

  2. 02

    Pain that worsens when lifting objects above the head or when abducting the arm

  3. 03

    Lateral chest pain (rib region) when breathing deeply

  4. 04

    Difficulty sleeping on the affected side

  5. 05

    Sensation of a "knot" or deep tension behind the scapula

  6. 06

    Pain radiating to the 4th and 5th fingers (serratus anterior pattern)

  7. 07

    Visible scapular dyskinesis — scapula that "wings" when pushing against a wall

  8. 08

    Worsens with overhead arm activities: hanging laundry, painting walls

Myths and facts about axillary and arm pain

Myth vs. Fact

MYTH

Axillary pain in women is always a sign of a breast problem

FACT

Axillary pain of breast origin generally accompanies other findings (nodule, skin change, nipple discharge). Isolated axillary pain, without breast findings on examination and mammography, is much more frequently of myofascial (trigger points in the serratus anterior and subscapularis) or musculoskeletal origin. Breast assessment is prudent but should not end the investigation if negative.

MYTH

If the pain radiates to the arm, it is a problem in the cervical spine

FACT

Cervical radiculopathy (C8-T1) causes pain on the medial side of the arm, but follows specific dermatomes and is accompanied by neurologic changes (grip weakness, reflex changes). Trigger points in the serratus anterior produce similar referred pain but without neurologic deficit and with reproduction of the pain on palpation of the muscle on the chest wall. The distinction is clinical and avoids unnecessary spinal investigations.

MYTH

Needling near the axilla is dangerous because of the lung

FACT

Needling of the serratus anterior requires precise anatomic knowledge and a tangential technique to the chest wall. When performed by a trained medical acupuncturist, the risk of pneumothorax is extremely low. The subscapularis is needled through the axillary border of the scapula — far from the pleural cavity. Safety depends on the training and experience of the professional.

The muscles everyone forgets to examine

Treatment protocol

Exclusion of serious causes
1st visit

Breast and axillary examination (lymph nodes). Cardiac assessment if left-sided pain with risk factors. Neurologic examination for C8-T1 roots. If serious causes are excluded, palpation of the serratus anterior and subscapularis to reproduce symptoms — diagnostic confirmation.

Needling of the serratus anterior
Sessions 1–3

Patient in lateral decubitus. Identification of the digitations of the serratus over the ribs. Tangential needling to the chest wall (never perpendicular) with 30–40 mm needles. Gentle in-and-out technique to obtain the twitch response. Bilateral treatment if necessary.

Needling of the subscapularis
Sessions 3–6

Patient in lateral decubitus with the arm partially abducted to move the scapula away from the chest wall. Needle inserted through the axillary border of the scapula toward the subscapular fossa. Deep technique that requires experience — a "pop" sensation when crossing the subscapular fascia. 2 Hz electroacupuncture if chronic trigger points.

Scapulothoracic rehabilitation
Sessions 7–10

Scapular stabilization exercises: scapular retraction, depression, and rotation. Strengthening of the serratus anterior (push-up plus, against the wall). Postural correction of protracted shoulders. Stretching of the pectoralis minor (frequently shortened and contributing to dysfunction). Home maintenance program.

Clinical pearl: serratus dyspnea

Scientific basis

Frequently asked questions

FREQUENTLY ASKED QUESTIONS · 04

Frequently Asked Questions

If axillary pain is the main symptom and you are not up to date with the recommended breast screening, the physician may order a mammogram for diagnostic reassurance. However, isolated axillary pain without a palpable mass or other breast findings rarely originates from the breast. The medical acupuncturist evaluates the complete picture and refers for additional investigation when necessary.

The subscapularis is a deep muscle and needling can generate moderate discomfort — especially when the trigger point is very active. The twitch response (local contraction) in the subscapularis produces a deep sensation in the shoulder that can be intense but brief. Most patients tolerate the procedure well and report significant relief after the session.

Trigger points in the serratus anterior tend to respond quickly — perceptible improvement in 1–3 sessions. The subscapularis, being deeper and frequently more chronic, may take 4–6 sessions for significant improvement. Correction of scapulothoracic dysfunction with exercises is essential to prevent recurrence.

The risk exists in theory, but is minimized by the tangential technique to the chest wall. The trained medical acupuncturist inserts the needle parallel to the ribs, never perpendicular. This angulation, combined with the use of needles of appropriate length and precise knowledge of the anatomy of the chest wall, makes the procedure safe when performed by a qualified professional.