What are the causes of left shoulder pain?

Causes of Left Shoulder Pain

Left shoulder pain arises from the same pathological processes as right shoulder pain, with trauma being the predominant cause in acute presentations and rotator cuff disease dominating in patients over 35 years. 1

Traumatic Causes (Acute Onset)

Fractures are the most common traumatic etiology and include: 1

• Clavicle fractures 1
• Scapula fractures 1
• Proximal humerus fractures 1

Soft tissue injuries commonly involve: 1

• Rotator cuff tears (including massive tears requiring expedited surgical repair) 1
• Acromioclavicular ligament injuries 1
• Labroligamentous complex tears 1

Joint instability presents as: 1

• Glenohumeral dislocations (can be missed on AP views alone, requiring axillary or scapula-Y views) 1
• Acromioclavicular joint dislocations 1

Non-Traumatic Causes (Atraumatic or Chronic)

Rotator cuff pathology accounts for over two-thirds of all shoulder pain cases and includes: 2

• Rotator cuff tendinopathy 3
• Subacromial impingement syndrome 3
• Subacromial pain syndrome 3

Degenerative conditions are particularly common in patients over 35-40 years: 4, 5

• Glenohumeral osteoarthritis (accounts for 2-5% of shoulder pain) 6
• Acromioclavicular joint arthritis 4

Inflammatory conditions include: 6, 7

• Adhesive capsulitis (frozen shoulder, accounts for 6% of shoulder pain) 6
• Bursitis 6
• Calcific tendinitis 8

Other structural causes: 6

• Avascular necrosis 6
• Biceps tendon pathology 4

Referred Pain Sources

Cervical spine pathology can manifest as shoulder pain, particularly in the scapular region: 4

• Cervical radiculopathy with radiation down the arm 4
• Nerve compression syndromes 4

Age-Specific Patterns

Patients under 35 years predominantly experience: 4

• Instability-related injuries 4
• Labral tears 4
• Sports-related trauma 1

Patients over 35-40 years predominantly experience: 4, 5

• Rotator cuff disease 4, 5
• Degenerative changes 4, 5
• Osteoporotic fractures (can occur with minimal or unrecognized trauma) 5

Critical Red Flag Causes

Septic arthritis requires immediate evaluation when systemic symptoms are present: 4, 5

• Fever, chills, or constitutional symptoms 4

Vascular compromise is uncommon but debilitating: 1

• Axillary artery injury (more likely with proximal humeral fractures, open fractures, shoulder dislocations) 1
• Subclavian or brachial artery injury 1

Neurological injury in the trauma setting: 1

• Brachial plexus injury 1
• Peripheral nerve injury (axillary, suprascapular, radial, ulnar, median nerves) 1

Common Clinical Pitfall

Never assume absence of trauma means absence of fracture, especially in elderly patients where osteoporotic fractures occur with minimal or unrecognized trauma. 5 This is the single most dangerous diagnostic error in shoulder pain evaluation.