Residency · Residency · Chronic Pain Management

Chronic Shoulder Pain: Diagnosis and Interventional Options

Introduction

Chronic shoulder pain is the third most common musculoskeletal complaint in clinical practice, with a point prevalence of 18-26% in the adult population. The shoulder's remarkable range of motion comes at the cost of inherent instability, making it susceptible to a wide spectrum of pathology. Pain medicine specialists must be proficient in the differential diagnosis of shoulder pain generators, advanced diagnostic techniques, and a growing armamentarium of interventional options ranging from intra-articular injections to neuroablative procedures.

Functional Anatomy

The glenohumeral joint is a ball-and-socket articulation between the humeral head and the shallow glenoid fossa, stabilized by the labrum, joint capsule, and glenohumeral ligaments. The rotator cuff comprises four muscles: the supraspinatus (responsible for abduction and the most commonly injured), the infraspinatus (external rotation), the teres minor (external rotation), and the subscapularis (internal rotation). The subacromial bursa, located between the rotator cuff and the acromion, is a common site of inflammation. The acromioclavicular (AC) joint is a frequent source of superior shoulder pain, particularly in overhead athletes and in the setting of degenerative changes. The shoulder complex receives its innervation from the suprascapular nerve (C5-C6), which innervates the supraspinatus and infraspinatus and contributes up to 70% of shoulder joint afferents, the axillary nerve (C5-C6), and the lateral pectoral nerve.

Rotator Cuff Pathology

Spectrum of Disease

Rotator cuff pathology exists on a spectrum. Tendinopathy involves degenerative changes without full-thickness tear, is most common in the supraspinatus, and is characterized by disorganized collagen, neovascularization, and mucoid degeneration. Partial-thickness tears, with articular-sided tears being more common than bursal-sided, are often painful and functionally limiting. Full-thickness tears represent complete disruption of the tendon, and their prevalence increases with age — notably, 50% of patients over 60 have asymptomatic full-thickness tears on imaging. Massive tears involving two or more tendons are associated with superior migration of the humeral head and rotator cuff arthropathy.

Diagnosis

Physical examination provides the foundation for diagnosis. The Neer and Hawkins signs assess for impingement. The empty can test evaluates the supraspinatus. The external rotation lag sign targets the infraspinatus. The belly press and lift-off tests assess the subscapularis. Ultrasound is highly operator-dependent but offers dynamic assessment and, in experienced hands, achieves 92% sensitivity and 94% specificity for full-thickness tears. MRI is the gold standard for rotator cuff evaluation, assessing tear size, retraction, muscle atrophy (Goutallier classification), and associated pathology.

Conservative Management

Structured physical therapy involving rotator cuff strengthening (particularly eccentric loading), scapular stabilization, and posterior capsule stretching produces improvement in 70-80% of patients with tendinopathy and partial tears. NSAIDs provide short-term symptom management. Subacromial corticosteroid injection offers short-term pain relief to facilitate rehabilitation, but should be limited to three injections per year due to the potential for tendon weakening.

<image>Anatomical illustration of the shoulder in coronal cross-section showing the four rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis) with their insertions on the greater and lesser tuberosities, the subacromial bursa, the acromion, and the course of the suprascapular nerve through the suprascapular notch beneath the transverse scapular ligament, with all structures clearly labeled</image>

Differential Diagnosis of Chronic Shoulder Pain

Adhesive Capsulitis (Frozen Shoulder)

Adhesive capsulitis is a progressive fibrotic contracture of the glenohumeral joint capsule that results in painful and restricted active and passive range of motion in a capsular pattern — external rotation is most limited, followed by abduction, then internal rotation. The condition progresses through three stages: the freezing phase (pain-predominant, lasting 2-9 months), the frozen phase (stiffness-predominant, lasting 4-12 months), and the thawing phase (gradual recovery, lasting 5-24 months). Risk factors include diabetes mellitus (prevalence 10-36% in diabetic patients), thyroid disease, female sex, age 40-60, and prolonged immobilization.

Treatment is stage-dependent. Physical therapy should emphasize gentle range-of-motion exercises during the freezing phase and progress to more aggressive stretching during the frozen and thawing phases. Intra-articular corticosteroid injection has strong evidence for short-term pain relief and improved range of motion, particularly during the freezing phase. Hydrodilatation (hydraulic distension) involves injecting 20-40 mL of saline with corticosteroid and local anesthetic to distend and rupture the contracted capsule under fluoroscopic or ultrasound guidance. Manipulation under anesthesia is reserved for refractory cases but carries risks of humeral fracture and rotator cuff tear. Arthroscopic capsular release is the definitive treatment for recalcitrant adhesive capsulitis.

Suprascapular Nerve Blocks

The suprascapular nerve (SSN) is a mixed motor-sensory nerve arising from C5-C6 that provides the majority of sensory innervation to the posterior glenohumeral joint capsule. SSN blocks are indicated for chronic shoulder pain from adhesive capsulitis, rotator cuff disease, glenohumeral osteoarthritis, and post-surgical pain, and serve as both a diagnostic and therapeutic tool. Anatomically, the nerve traverses the suprascapular notch beneath the transverse scapular ligament, courses through the spinoglenoid notch, and innervates the supraspinatus and infraspinatus muscles. The block is performed under ultrasound or fluoroscopic guidance, targeting the nerve at the suprascapular notch (for a complete sensory and motor block) or the spinoglenoid notch (to spare supraspinatus function).

Multiple RCTs demonstrate significant pain reduction and functional improvement with SSN block. A 2019 meta-analysis showed that SSN block is equivalent to intra-articular corticosteroid for adhesive capsulitis, with a more favorable safety profile. Pulsed radiofrequency of the SSN at the suprascapular notch offers non-ablative neuromodulation with evidence supporting 3-6 months of pain relief without motor deficit.

<image>Ultrasound-guided suprascapular nerve block illustration showing the ultrasound probe positioned over the suprascapular fossa, with a corresponding sonographic image demonstrating the suprascapular notch, transverse scapular ligament, suprascapular artery (above the ligament), and suprascapular nerve (below the ligament), with the needle trajectory approaching the nerve in-plane and local anesthetic spread around the nerve</image>

Intra-Articular Injections

Glenohumeral Joint Injections

Corticosteroid injections — triamcinolone 40 mg or methylprednisolone 40 mg with local anesthetic — are typically performed via a posterior approach under ultrasound guidance. Evidence supports short-term (4-8 weeks) pain relief. Hyaluronic acid (viscosupplementation) has mixed evidence for glenohumeral osteoarthritis but may provide 3-6 months of benefit in select patients; it is not FDA-approved for the shoulder but is used off-label. Platelet-rich plasma (PRP) has emerging evidence for partial rotator cuff tears and early glenohumeral osteoarthritis, with leukocyte-poor PRP preferred; the evidence base is growing but not yet definitive.

Acromioclavicular Joint Injections

The AC joint is diagnosed as a pain source through point tenderness over the joint and a positive cross-body adduction test; diagnostic injection with local anesthetic is confirmatory. The injection uses a direct superior approach with ultrasound guidance, and because the joint is small, only 0.5-1.0 mL of volume is required. Treatment consists of corticosteroid injection, with PRP or prolotherapy considered for chronic AC joint pain.

Genicular-Style Denervation Approaches for the Shoulder

Analogous to genicular nerve ablation for chronic knee pain, radiofrequency ablation of the articular branches supplying the shoulder is an emerging approach. The target nerves are the articular branches of the suprascapular nerve, axillary nerve, and lateral pectoral nerve that innervate the glenohumeral joint capsule. The rationale is selective sensory denervation of the joint capsule while preserving motor function to the rotator cuff. The technique involves diagnostic blocks of the articular branches under ultrasound or fluoroscopic guidance, followed by thermal or cooled radiofrequency ablation in confirmed responders.

Early case series and pilot studies demonstrate feasibility and promising short-term outcomes, with several RCTs underway. Compared to full suprascapular nerve ablation, articular branch ablation aims to avoid the motor weakness (supraspinatus and infraspinatus atrophy) that can result from ablating the entire nerve trunk. This approach remains investigational, and further evidence is needed before widespread adoption.

<image>Posterior view anatomical illustration of the shoulder showing the articular nerve branches targeted for shoulder denervation, including branches from the suprascapular nerve at the suprascapular and spinoglenoid notches, the articular branch of the axillary nerve in the quadrilateral space, and the lateral pectoral nerve contribution, with proposed radiofrequency ablation target points marked and labeled</image>

Clinical Pearls

The suprascapular nerve block is an underutilized tool for chronic shoulder pain — it provides up to 70% of shoulder joint afferent blockade and can serve as both a diagnostic and therapeutic intervention. Intrinsic shoulder pathology must always be differentiated from referred pain sources, including cervical radiculopathy at C5-C6, Pancoast tumor, and diaphragmatic irritation. Full-thickness rotator cuff tears are frequently asymptomatic, especially in older adults, so imaging findings must be carefully correlated with the clinical presentation before attributing pain to structural pathology. In adhesive capsulitis, combining intra-articular corticosteroid injection with physical therapy yields better outcomes than either intervention alone. Genicular-style denervation of the shoulder represents an exciting frontier in interventional pain management, but it requires rigorous RCT evidence before it can be considered standard of care.

References

1. Hanchard NC, Lenza M, Handoll HH, Takwoingi Y. Physical tests for shoulder impingement and local lesions of bursa, tendon or labrum that may accompany impingement. Cochrane Database Syst Rev. 2013;(4):CD007427.
2. Chang KV, Hung CY, Wu WT, Han DS, Yang RS, Lin CP. Comparison of the effectiveness of suprascapular nerve block with physical therapy, intra-articular corticosteroid injection, and combined treatments in patients with adhesive capsulitis. Arch Phys Med Rehabil. 2019;100(3):564-574.
3. Neviaser AS, Hannafin JA. Adhesive capsulitis: a review of current treatment. Am J Sports Med. 2010;38(11):2346-2356.
4. Tran J, Peng PWH, Agur AMR. Anatomical study of the innervation of glenohumeral and acromioclavicular joint capsules: implications for image-guided intervention. Reg Anesth Pain Med. 2019;44(4):452-458.

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