Differential Diagnosis for Pain on Shoulder Extension

The following differential diagnosis is organized into categories to help guide the thought process:

• Single Most Likely Diagnosis

  • Subacromial Impingement: This is the most likely diagnosis due to the mechanics of shoulder extension, which can cause the rotator cuff tendons to impinge against the acromion, leading to pain.

• Other Likely Diagnoses

  • Rotator Cuff Tendinopathy: Inflammation or degeneration of the rotator cuff tendons can cause pain during shoulder extension due to increased tension on the affected tendons.
  • Adhesive Capsulitis (Frozen Shoulder): While more commonly associated with limited range of motion, pain on extension can be a feature, especially in the early stages of the disease.
  • Glenohumeral Osteoarthritis: Degenerative changes in the shoulder joint can lead to pain with movement, including extension, due to joint space narrowing and bone-on-bone contact.

• Do Not Miss Diagnoses

  • Fracture (e.g., Humeral Fracture): Although less common, a fracture could present with pain on shoulder extension, especially if the fracture involves the humeral head or neck.
  • Infection (e.g., Septic Arthritis): Infection within the shoulder joint can cause severe pain with any movement, including extension, and is a medical emergency.

• Rare Diagnoses

  • Quadrilateral Space Syndrome: Compression of the axillary nerve and/or posterior circumflex humeral artery within the quadrilateral space can lead to pain and weakness, potentially worsening with certain movements like extension.
  • Tumors (e.g., Bone or Soft Tissue Tumors): Although rare, tumors affecting the shoulder region can cause pain with movement, including extension, and should be considered in the differential diagnosis, especially with atypical presentations or systemic symptoms.