Differential Diagnosis for Shoulder Pain

The patient presents with positive impingement signs, pain with resisted forward flexion and abduction, and tenderness to palpation over the anterior shoulder. Based on these symptoms, the following differential diagnoses are considered:

• Single Most Likely Diagnosis

  • Subacromial Impingement Syndrome: This condition is characterized by the compression of the rotator cuff tendons and/or subacromial bursa between the humeral head and the acromion, leading to pain and limited mobility. The patient's symptoms of positive impingement signs, pain with resisted forward flexion and abduction, and anterior shoulder tenderness are classic for this diagnosis.

• Other Likely Diagnoses

  • Rotator Cuff Tendinopathy: Inflammation or degeneration of the rotator cuff tendons can cause pain with resisted movements and tenderness over the affected area, which aligns with the patient's symptoms.
  • Bicipital Tendinopathy: Inflammation of the long head of the biceps tendon can cause anterior shoulder pain, especially with forward flexion and abduction, fitting the patient's presentation.
  • Adhesive Capsulitis (Frozen Shoulder): Although typically characterized by stiffness and limited range of motion, early stages can present with pain similar to the patient's symptoms, especially if there's an underlying inflammatory process.

• Do Not Miss Diagnoses

  • Fracture (e.g., Humeral Head or Scapula): Although less likely given the description, a fracture could present with pain and tenderness, especially if there was a recent trauma. Missing this diagnosis could lead to significant morbidity.
  • Infection (e.g., Septic Arthritis or Osteomyelitis): Infections in the shoulder joint or bone can cause severe pain, tenderness, and limited mobility. These conditions are medical emergencies requiring prompt diagnosis and treatment.
  • Neer's Type III Acromion: A hooked acromion can cause significant impingement on the rotator cuff, leading to chronic pain and dysfunction. While not immediately life-threatening, missing this diagnosis could lead to prolonged suffering and necessitate surgical intervention.

• Rare Diagnoses

  • Quadrilateral Space Syndrome: Compression of the axillary nerve and/or posterior circumflex humeral artery within the quadrilateral space can cause shoulder pain and weakness, although it's less common and typically presents with specific patterns of weakness and numbness.
  • Suprascapular Neuropathy: Compression of the suprascapular nerve can cause pain and weakness in the shoulder, particularly affecting the supraspinatus and infraspinatus muscles. This condition is less common and might present with atrophy and specific patterns of weakness.