Supraspinatus: Trigger Points and Shoulder Pain

The Supraspinatus Muscle

The supraspinatus (supraspinatus muscle) is the most frequently injured muscle of the rotator cuff and the first to initiate shoulder abduction. Despite being relatively small, its biomechanical role is disproportionate to its size: it is the muscle that stabilizes the humeral head in the glenoid cavity and initiates the first degrees of arm elevation — exactly the movement we use hundreds of times a day without noticing.

Myofascial trigger points of the supraspinatus are an underdiagnosed cause of lateral shoulder pain. Frequently confused with rotator cuff tendinopathy or subacromial impingement syndrome, these trigger points produce deep pain in the deltoid region that mimics tendon lesions — leading to unnecessary imaging studies and, in some cases, to surgeries that do not resolve the complaint because the myofascial origin was not identified.

Anatomy and Function

The supraspinatus muscle originates in the supraspinous fossa of the scapula, occupying the entire extent of this bony depression above the spine of the scapula. Its fibers converge laterally, pass under the acromion and the coracoacromial ligament, and insert into the superior facet of the greater tubercle of the humerus (greater tuberosity). This tendinous insertion is the most vulnerable structure of the rotator cuff — the most common site of tendinopathy, partial tear, and complete tear.

The function of depressor of the humeral head is frequently underestimated. During shoulder abduction, the deltoid pulls the humerus upward. Without the stabilizing action of the supraspinatus (and other cuff muscles), the humeral head would migrate superiorly and collide with the acromion — exactly what occurs in subacromial impingement syndrome when the supraspinatus is weakened or injured.

The supraspinatus is innervated by the suprascapular nerve (C5-C6), which travels through the suprascapular notch under the superior transverse scapular ligament. This anatomical course makes the nerve vulnerable to compression — suprascapular neuropathy is an important differential diagnosis in deep shoulder pain and may coexist with trigger points in the supraspinatus.

Trigger Points of the Supraspinatus

Myofascial trigger points of the supraspinatus are located in the muscle belly, within the supraspinous fossa, deep to the trapezius muscle. Palpation requires firm pressure directed inferiorly, perpendicular to the fossa, with the trapezius relaxed. The supraspinatus has two main trigger points, each with a distinct but overlapping referred pain pattern.

TrP1 of the supraspinatus is clinically the most relevant and one of the trigger points most frequently encountered in patients with a complaint of "shoulder pain". Its importance lies in the fact that the referred pain — deep, diffuse, in the lateral aspect of the deltoid — is clinically indistinguishable from the pain of supraspinatus tendinopathy. This means that without systematic myofascial palpation, differential diagnosis is impossible.

Referred pain from TrP1 may radiate distally along the lateral arm, reaching the lateral epicondyle of the elbow. Patients frequently report "pain running down the outer arm" — a complaint that can be confused with C5 cervical radiculopathy, although the distribution does not follow a classic dermatome. Differentiating from radicular pain relies on neurological examination (no strength or reflex deficit in myofascial syndrome) and on reproducing pain by palpating the trigger point.

Referred Pain Pattern

The referred pain of the supraspinatus is one of the most clinically relevant among all muscles of the rotator cuff, because it almost perfectly mimics the pain of tendinopathy and subacromial impingement syndrome. The patient localizes the pain as "deep in the shoulder, on the outside" — pointing consistently to the region of the middle deltoid with the flat hand, not with the index finger, indicating diffuse and poorly localized pain.

The painful arc is the most characteristic clinical finding — both in tendinopathy and in trigger points of the supraspinatus. The pain typically arises between 60° and 120° of active abduction, exactly in the range in which the supraspinatus tendon is compressed under the coracoacromial arch. In trigger points, the pain of the painful arc results from contraction of the shortened muscle against resistance in the intermediate range of motion — not from mechanical compression of the tendon.

Nocturnal pain is another classic complaint. Lying on the affected shoulder compresses the supraspinatus against the supraspinous fossa, activating the trigger points. Lying on the opposite side may also provoke pain by passive lengthening of the shortened muscle. Many patients develop insomnia or sleep fragmentation by not finding a comfortable position — which contributes to central sensitization and chronification of pain.

Causes and Risk Factors

Supraspinatus trigger points develop through a combination of mechanical overload, repetitive microtrauma, and predisposing anatomical factors. Understanding the causes is essential for effective treatment and for prevention of recurrences — without addressing perpetuating factors, trigger points tend to reactivate.

The relationship between tendinopathy and trigger points in the supraspinatus is bidirectional and clinically relevant. Chronic tendinopathy alters the biomechanics of the shoulder and overloads the muscle belly, activating trigger points. In turn, active trigger points shorten the muscle, increase tension on the tendon, and reduce local perfusion — perpetuating and aggravating the tendinopathy. This interdependence explains why isolated treatment of only one of the conditions frequently fails.

The supraspinatus is the rotator cuff tendon most commonly torn. It is estimated that 70% of all rotator cuff tears involve the supraspinatus, in isolation or in combination with other tendons. The hypovascular zone of the tendon — located approximately 1 cm before the insertion on the greater tubercle — is especially vulnerable due to relatively insufficient blood supply, mainly in the age range above 40 years.

Tendinopathy versus Trigger Point: Clinical Differentiation

The differentiation between supraspinatus tendinopathy and myofascial trigger points is one of the greatest clinical challenges in the evaluation of the painful shoulder. Both conditions produce lateral shoulder pain, positive painful arc, and functional weakness. Magnetic resonance imaging frequently shows tendinous alterations in asymptomatic patients above 40 years, hindering causal attribution.

In practice, the two conditions frequently coexist. The ideal clinical approach is to treat the trigger points first — if pain improves significantly, the myofascial component was the main pain generator, regardless of MRI findings. If pain persists despite inactivation of trigger points, the tendinous lesion may be the primary source and requires additional approach.

Subacromial Impingement Syndrome

Subacromial impingement syndrome is the most common cause of shoulder pain in adults and is intimately related to the supraspinatus. In this syndrome, the supraspinatus tendon is repeatedly compressed between the head of the humerus and the coracoacromial arch (formed by the acromion, coracoacromial ligament, and coracoid process) during arm elevation.

The relationship between supraspinatus trigger points and impingement syndrome is circular: the impingement syndrome activates trigger points by mechanical stress on the muscle, and the trigger points weaken and shorten the supraspinatus, reducing its capacity to depress the humeral head — which aggravates the compression. Breaking this cycle is the main objective of treatment with medical acupuncture.

Diagnosis

The diagnosis of trigger points in the supraspinatus is clinical, based on detailed history, physical examination of the shoulder, and systematic myofascial palpation. Magnetic resonance imaging of the shoulder is frequently requested to assess the integrity of the tendon and the subacromial bursa, but its findings should be correlated with the clinical picture — incidental findings are extremely common.

Palpation of the supraspinatus is more difficult than that of the trapezius because of the depth of the muscle and the overlap of the upper trapezius. The most effective technique is to position the patient seated, with the arm relaxed at the side of the body, and palpate the supraspinous fossa with the thumb directed inferiorly, sliding under the upper border of the trapezius. Reproduction of the referred pain in the lateral aspect of the shoulder confirms the diagnosis of active trigger point.

Musculoskeletal ultrasound is a valuable tool for evaluating the supraspinatus: it allows simultaneous assessment of the tendon (tendinopathy, tear, calcification), the subacromial bursa (bursitis), and the muscle belly (trophism, fatty infiltration). In experienced hands, it can identify the tense band of the trigger point as a hypoechoic area in the muscle belly — although this finding is not necessary for clinical diagnosis.

Differential Diagnosis

Lateral shoulder pain is one of the most common musculoskeletal symptoms and has a broad differential diagnosis. The acupuncture physician should systematically evaluate alternative causes before attributing all symptoms to supraspinatus myofascial syndrome — especially because multiple conditions frequently coexist.

Supraspinatus versus C5 radiculopathy

Distinguishing supraspinatus trigger points from C5 cervical radiculopathy is clinically important because both produce pain in the deltoid region. In myofascial syndrome, the pain is deep and poorly localized, without neurological deficit — strength, reflexes, and sensation are normal. In C5 radiculopathy, there is objective weakness of the deltoid and biceps, a diminished biceps reflex, and paresthesias in the C5 dermatome (lateral shoulder). The Spurling test (axial compression with cervical extension and rotation) reproduces the radicular pain.

Trigger points and MRI: the false-positive trap

One of the greatest challenges in evaluating the painful shoulder is the high prevalence of incidental findings on magnetic resonance imaging. Population studies show that tendinopathy, partial tear, and degenerative alterations of the supraspinatus are found in a significant proportion of completely asymptomatic individuals above 40 years. Attributing the patient's pain to these imaging findings, without adequate clinical correlation, can lead to unnecessary treatments — including surgeries — while the trigger points responsible for the pain remain undiagnosed.

Treatments

Treatment of trigger points of the supraspinatus is multimodal: it combines direct interventions on the trigger point (dry needling, medical acupuncture) with progressive shoulder rehabilitation (pendulum exercises, eccentric strengthening, correction of scapular dyskinesis). The isolated approach — only needling without rehabilitation, or only exercises without deactivating trigger points — has inferior results.

The Codman pendulum exercise is the first line of mobility in the painful supraspinatus: the patient leans the trunk forward, lets the affected arm hang by gravity, and performs small circular movements. This moves the glenohumeral joint without contracting the rotator cuff, maintaining mobility and promoting local circulation without aggravating the trigger points.

Eccentric strengthening is the rehabilitation strategy with the best evidence for rotator cuff tendinopathies and for prevention of trigger point recurrence. Eccentric exercises — in which the muscle is lengthened while generating force — stimulate tendon remodeling and increase muscle resistance to fatigue. The classic exercise is abduction with light weight (0.5-1 kg) with slow and controlled lowering of the arm.

Medical Acupuncture and Dry Needling

Medical acupuncture is one of the most effective approaches for trigger points of the supraspinatus. Needling of the supraspinatus requires precise anatomical knowledge, since the muscle lies deep to the upper trapezius and its fossa is bounded medially by the spine of the scapula. The needle should be directed perpendicularly to the fossa, with controlled depth, until obtaining the local twitch response that confirms deactivation of the trigger point.

Obtaining the local twitch response is considered a relevant clinical marker in trigger point needling. When the needle reaches the nodule, a brief and involuntary contraction of the muscle belly is observed, frequently accompanied by momentary reproduction of the referred pain followed by relief. Part of the literature suggests that sessions with multiple twitch responses may show better clinical outcomes, although this correlation is not fully established.

Prognosis

The prognosis of isolated supraspinatus trigger points is good to excellent when treated with adequate needling and progressive rehabilitation. Most patients show significant improvement in pain and functional recovery after 4-8 sessions of medical acupuncture, provided that perpetuating factors are simultaneously addressed.

The prognosis is more reserved when trigger points coexist with significant tendinopathy, partial tear, or advanced impingement syndrome. In these cases, myofascial treatment improves pain and function, but additional treatment of the structural lesion may be necessary. Advanced age, prolonged disuse, and the presence of fatty infiltration in the muscle belly (indicating denervation or chronic atrophy) are factors of worse prognosis.

The prevention of recurrences depends fundamentally on the home program of rotator cuff strengthening and on the correction of biomechanical factors — especially scapular dyskinesis and weakness of the scapular stabilizers (serratus anterior, middle and lower trapezius). Patients who abandon rehabilitation after pain relief have a significantly higher recurrence rate.

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