Differential Diagnosis for Right Shoulder Pain

The patient presents with sudden onset of sharp shoulder pain and aching sensation radiating down the arm, worsened by fast movements and certain shoulder positions. Given the history and physical examination findings, the differential diagnoses can be categorized as follows:

• Single Most Likely Diagnosis

  • Rotator Cuff Tendinopathy or Tear: The patient's symptoms of sharp pain at the shoulder joint, aching sensation radiating down the arm, and pain triggered by certain shoulder positions are consistent with rotator cuff pathology. The history of prior shoulder issues and the physical examination findings of limited active internal rotation and shoulder abduction, along with the inability to move the hand off the back on external rotation against resistance, support this diagnosis.

• Other Likely Diagnoses

  • Adhesive Capsulitis (Frozen Shoulder): Although the patient has a full range of motion in the neck and no significant tenderness on palpation, the limited active internal rotation and shoulder abduction could suggest early stages of adhesive capsulitis, especially given the history of prior shoulder issues.
  • Subacromial Bursitis: The patient's pain pattern and exacerbation with rapid movements could be consistent with subacromial bursitis, which often presents with pain in the shoulder region that may radiate down the arm.
  • Labral Tear: The sharp pain at the shoulder joint and the specific movements that trigger pain could indicate a labral tear, which might have occurred without a significant traumatic event.

• Do Not Miss Diagnoses

  • Thoracic Outlet Syndrome: Although the patient denies neck pain, thoracic outlet syndrome could cause shoulder and arm pain due to compression of the nerves and/or blood vessels. It's crucial to consider this diagnosis due to its potential for significant morbidity if missed.
  • Referred Pain from Cardiac or Pulmonary Issues: Despite the absence of chest pain or shortness of breath, it's essential to consider cardiac or pulmonary causes of referred pain to the shoulder, especially in patients with risk factors. The patient's history of smoking (although quit in 2014) and the presence of hypertension are notable.
  • Infection or Septic Arthritis: Although the patient does not have fever or significant swelling, infection should always be considered, especially if the pain is severe and unexplained by other causes.

• Rare Diagnoses

  • Polymyalgia Rheumatica: This condition could present with shoulder pain and stiffness, but it typically involves both shoulders and is accompanied by systemic symptoms such as fever and weight loss, which are not present in this case.
  • Tumors (Bone or Soft Tissue): Although rare, tumors could cause shoulder pain. The absence of systemic symptoms, night pain, or significant weight loss makes this less likely, but it remains a consideration in the differential diagnosis, especially if other causes are ruled out.