What causes posterior lateral shoulder pain in an adult with no significant medical history?

Posterior Lateral Shoulder Pain: Differential Diagnosis and Evaluation

Posterior lateral shoulder pain in an adult without trauma most commonly results from rotator cuff tendinopathy (particularly supraspinatus and infraspinatus), posterior capsular contracture, or cervical radiculopathy—with the exact location and radiation pattern being critical to distinguish between these entities. 1, 2, 3

Primary Diagnostic Considerations

Rotator Cuff Pathology (Most Common in Adults >35-40 Years)

In patients over 35-40 years, rotator cuff disease and degenerative changes are the predominant causes of chronic shoulder pain, with posterior lateral pain specifically suggesting supraspinatus or infraspinatus tendinopathy. 1, 2

Key clinical features include:

• Pain during overhead activities and weakness, particularly with movements that load the rotator cuff eccentrically 2
• Focal weakness with decreased range of motion during abduction with external or internal rotation 4, 2
• Positive empty can test (92% sensitive) and positive Neer's test (88% sensitive) 2
• Pain typically occurs during the deceleration phase of repetitive movements when rotator cuff muscles work eccentrically 2

Scapular dyskinesis contributes significantly to rotator cuff injury and must be assessed, as poor scapular coordination may be both cause and effect of the underlying pathology. 4, 2

Posterior Capsular Contracture

Posterior capsular contracture presents with restricted internal rotation and reproduction of pain in the posterior lateral shoulder, often mimicking impingement syndrome but distinguished by limited passive range of motion. 5

Clinical presentation includes:

• Restricted internal rotation with pain reproduction during this motion 5
• Increased anterosuperior translation of the humeral head with forward flexion 5
• Normal range of motion would suggest impingement syndrome instead 5

Cervical Radiculopathy (Critical to Rule Out)

Chronic shoulder pain radiating down the arm without trauma strongly suggests cervical spine pathology with nerve root compression, characterized by numbness, tingling, weakness, or radiation of pain down the arm. 1

Distinguishing features include:

• Numbness, tingling, or weakness in specific dermatomal distributions (C5, C6, C7, or C8) 4, 1
• Regional sensory changes, allodynia, or hyperpathia suggesting neuropathic pain component 4, 1
• Pain radiation pattern following a specific cervical nerve root distribution 1

Do not assume it is simply "muscle tension" or "muscle spasm" without ruling out structural cervical spine pathology—imaging should not be delayed if red flags are present. 1

Diagnostic Algorithm

Step 1: Document Exact Pain Location and Radiation

The exact pain location is critical for diagnosis: 1, 2

• Anterior shoulder suggests rotator cuff or biceps pathology 1, 2
• Superior shoulder indicates acromioclavicular joint disease 2
• Posterior lateral or scapular region may indicate rotator cuff pathology or referred pain from cervical spine 1, 2

If pain radiates down the arm with numbness, tingling, or weakness, cervical radiculopathy is the primary concern and requires cervical spine imaging. 1

Step 2: Physical Examination Maneuvers

Perform specific tests to differentiate rotator cuff pathology from other causes: 2

• Hawkins' test (92% sensitive) and Neer's test (88% sensitive) for rotator cuff impingement 2
• Empty can test and external rotation weakness testing for rotator cuff tears 2, 3
• Assess passive range of motion: limited and painful passive motion suggests adhesive capsulitis or posterior capsular contracture, while preserved passive motion with painful/weak active motion suggests rotator cuff pathology 2, 5
• Test internal rotation specifically: restricted internal rotation with pain reproduction indicates posterior capsular contracture 5

Test for neurological symptoms including sensory changes, allodynia, or hyperpathia to identify neuropathic pain components. 4, 1

Step 3: Imaging Strategy

If cervical radiculopathy is suspected based on radiation pattern and neurological symptoms: 1

• MRI of the cervical spine without contrast is the preferred initial advanced imaging, as it directly visualizes disc herniations, osteophytes, and nerve root compression 1
• Plain radiographs of the cervical spine may be obtained first to assess for gross structural abnormalities, though they cannot visualize disc herniations or nerve roots 1
• Consider electrodiagnostic testing if imaging is negative or equivocal, with sensitivity over 80% and specificity of 95% for confirming nerve compression 1

If rotator cuff pathology is suspected based on physical examination: 2, 3

• MRI or ultrasonography are preferred for rotator cuff disorders 3
• Plain radiographs may help diagnose massive rotator cuff tears 3

Shoulder MRI is recommended only if physical examination suggests concurrent rotator cuff pathology, not as a first-line test. 1

Initial Management Approach

If Rotator Cuff Pathology is Confirmed

Most rotator cuff pathology can initially be managed conservatively without surgical intervention, with a focus on rehabilitation and pain management. 1, 2

Initial management includes: 4, 2

• Complete rest from aggravating activities until asymptomatic 4, 2
• Improvement of range of motion through stretching and mobilization techniques, focusing especially on external rotation and abduction 4, 2
• Rotator cuff and scapular stabilizer strengthening once pain-free motion is achieved 4, 2
• Modalities including ice, heat, and soft tissue massage 4, 2
• NSAIDs for acute pain management 2
• Corticosteroid injections for more severe cases 2

Refer to a rehabilitation specialist for comprehensive management if conservative measures fail. 1

If Posterior Capsular Contracture is Confirmed

Initial management should be nonsurgical, emphasizing range-of-motion stretching with the goal of restoring normal motion, particularly internal rotation. 5

For patients who fail nonsurgical management, arthroscopic posterior capsule release can result in improved motion and pain relief. 5

If Cervical Radiculopathy is Confirmed

If cervical radiculopathy is confirmed, consider continuing or initiating pregabalin as it may provide therapeutic benefit for neuropathic pain, with a typical adult regimen of 300-600 mg daily in divided doses. 1

Alternative nerve-stabilizing agents include gabapentin or duloxetine for pain management. 1

Consider botulinum toxin type A injections into affected muscles for cervical dystonia or muscle spasms. 1

Critical Pitfalls to Avoid

Do not assume absence of trauma means absence of significant pathology—rotator cuff tears and cervical radiculopathy commonly occur without recognized trauma, especially in patients over 35-40 years. 1, 2

Avoid overhead pulley exercises, which encourage uncontrolled abduction and can worsen rotator cuff pathology. 4

Do not delay cervical spine imaging if neurological symptoms are present—cervical radiculopathy requires different management than primary shoulder pathology. 1