What are the differential diagnoses for posterior shoulder pain radiating to the elbow?

Differential Diagnosis: Posterior Shoulder Pain Radiating to Elbow

The primary differential diagnoses for posterior shoulder pain radiating to the elbow include cervical radiculopathy (C6-C7 nerve root compression), rotator cuff pathology (particularly infraspinatus/teres minor tendinopathy or tears), triceps tendinopathy with possible avulsion, posterior glenohumeral joint pathology, and referred pain from thoracic outlet syndrome.

Neurologic Etiologies (Most Critical to Rule Out)

• Cervical spine pathology is the most important consideration when pain radiates below the elbow, particularly if accompanied by motor weakness or sensory changes 1
• Radiating pain with neurologic symptoms strongly suggests nerve root compression from herniated disc, foraminal stenosis, or spinal cord lesions 1
• C6-C7 radiculopathy classically produces posterior shoulder and arm pain extending to the elbow and beyond 1
• Thoracic outlet syndrome (scalene muscle compression, cervical rib, or first rib abnormalities) can produce similar radiation patterns with combined neural and vascular symptoms 1

Clinical pitfall: Patients often describe shoulder pain misleadingly because the shoulder's movable fulcrum may be a secondary irritant rather than the primary pathology—the actual source may be as proximal as the spinal cord 1

Intrinsic Shoulder Pathology

Rotator Cuff Disorders

• Posterior rotator cuff tears (infraspinatus, teres minor) present with pain during overhead activities and weakness on external rotation testing 2
• Chronic rotator cuff tendinopathy can produce diffuse posterior shoulder pain that may radiate distally 2
• Key examination findings: Positive empty can test, external rotation weakness, and positive impingement signs suggest rotator cuff pathology 2

Triceps Tendon Pathology

• Triceps tendinopathy or partial tears can cause posterior elbow pain that refers proximally to the posterior shoulder 3
• Avulsion fractures of the olecranon from triceps insertion may occur with acute trauma 3
• Look for olecranon enthesophytes on imaging, which suggest chronic triceps tendon stress 3

Glenohumeral Joint Disease

• Posterior glenohumeral instability or labral tears can produce posterior shoulder pain 4
• Glenohumeral osteoarthritis in patients >50 years presents with gradual pain and loss of motion 2
• Adhesive capsulitis causes diffuse shoulder pain with restricted passive range of motion (particularly external rotation) and is associated with diabetes and thyroid disorders 2

Postural and Referred Pain

• Postural abnormalities and cervical spine disorders are common extrinsic causes of shoulder pain 5
• Scapular dyskinesis from poor posture can create posterior shoulder pain that worsens with arm use 6

Diagnostic Approach

Initial Clinical Assessment

• Determine if pain extends below the elbow with motor/sensory changes—this mandates cervical spine evaluation 1
• Perform cervical spine range of motion and Spurling's test to assess for radiculopathy 1
• Test rotator cuff strength (external rotation, empty can test) and check for impingement signs 2
• Assess for glenohumeral instability with apprehension and relocation tests 2
• Palpate the triceps insertion at the olecranon for tenderness 3

Imaging Algorithm

• Plain radiographs of the shoulder (AP, lateral, scapular Y views) are the mandatory first imaging study to exclude fractures, dislocations, massive rotator cuff tears, and arthritis 7, 8
• If elbow involvement is suspected, obtain standard elbow radiographs (AP, lateral, oblique) to identify avulsion fractures, joint effusions, or heterotopic ossification 7
• Cervical spine radiographs or MRI are indicated when neurologic symptoms are present or pain radiates below the elbow with sensory/motor changes 1
• MRI shoulder without contrast is reserved for persistent symptoms after 4-6 weeks of conservative management to evaluate rotator cuff tears, labral pathology, or occult soft tissue injury 8
• Dynamic ultrasound can detect triceps pathology and has 96% sensitivity for detecting dynamic nerve or tendon abnormalities when clinical suspicion remains high 7

Critical Decision Points

• Neurologic deficit (weakness, numbness below elbow) = cervical spine imaging and possible neurosurgical referral 1
• Gross shoulder instability on examination = urgent orthopedic referral 8
• Suspected triceps avulsion or complete rotator cuff tear = orthopedic consultation 3, 4
• Most other presentations = trial of conservative management for 4-6 weeks before advanced imaging 8

Common Pitfalls to Avoid

• Do not assume the shoulder joint is the primary pathology when pain radiates to the elbow—always assess the cervical spine 1
• Avoid ordering MRI as initial imaging; plain radiographs must come first 7, 8
• Do not miss posterior sternoclavicular dislocation, which requires urgent surgical referral 4
• Static imaging may miss dynamic pathology; consider dynamic ultrasound or stress fluoroscopy if symptoms persist despite negative MRI 7