Differential Diagnosis for Bilateral Shoulder Pain

Single Most Likely Diagnosis

• Subacromial Bursitis or Rotator Cuff Tendinopathy: This condition is characterized by pain in the deltoid region, especially with movements that aggravate the rotator cuff and subacromial bursa, such as reaching backward and internal rotation. The absence of pain with upward reaching and the presence of mild tenderness on palpation of the deltoid muscle support this diagnosis.

Other Likely Diagnoses

• Adhesive Capsulitis (Frozen Shoulder): Although typically unilateral, bilateral cases can occur. The gradual onset of pain and stiffness, especially with movements like internal rotation, could suggest early stages of adhesive capsulitis.
• Deltoid Strain: Given the location of pain and tenderness, a strain of the deltoid muscle itself could be considered, especially if the patient has been engaging in activities that involve heavy lifting or throwing.
• Scapulothoracic Bursitis: Inflammation of the bursae around the scapula can cause pain that radiates to the deltoid region, especially with movements that involve scapular rotation.

Do Not Miss Diagnoses

• Referred Pain from Cervical Spine: Cervical radiculopathy or cervical spondylosis can refer pain to the shoulder region. Although the patient denies recent trauma, chronic conditions or degenerative changes could be contributing to the pain.
• Polymyalgia Rheumatica (PMR): This condition is characterized by aching and stiffness in the shoulder girdle, which could be mistaken for localized shoulder pathology. The absence of systemic symptoms does not rule out PMR.
• Neoplastic or Metastatic Disease: Although rare, tumors affecting the shoulder or metastatic disease to the bone could present with gradual onset of pain without a clear precipitating event.

Rare Diagnoses

• Quadrilateral Space Syndrome: Compression of the axillary nerve and/or posterior circumflex humeral artery within the quadrilateral space can cause shoulder pain, but this is less common and typically associated with specific activities or anatomical variations.
• Parsonage-Turner Syndrome (Neuralgic Amyotrophy): An idiopathic condition characterized by acute onset of severe pain in the shoulder and arm, followed by weakness and atrophy. The gradual onset in this case makes it less likely, but it remains a rare consideration.