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 pain pattern, exacerbation with rapid movements, and limited active internal rotation and shoulder abduction are consistent with rotator cuff pathology. The history of prior shoulder issues treated with a steroid injection also supports this diagnosis, as recurrent or chronic shoulder pain can be indicative of ongoing rotator cuff disease.

• Other Likely Diagnoses

  • Early Stages of Adhesive Capsulitis: The patient's pain and limited range of motion, particularly with internal rotation and abduction, could be indicative of early adhesive capsulitis. However, the absence of significant stiffness and the fact that passive range of motion is normal make this less likely than rotator cuff tendinopathy.
  • Subacromial Bursitis: The patient's pain pattern and exacerbation with rapid movements could also suggest subacromial bursitis. However, the lack of tenderness on palpation of the shoulder joint and the specific limitations in active range of motion point more towards a rotator cuff issue.

• Do Not Miss Diagnoses

  • Thoracic Outlet Syndrome: Although less likely given the absence of neck pain and specific neurologic symptoms, thoracic outlet syndrome could cause shoulder and arm pain. Missing this diagnosis could lead to prolonged morbidity.
  • Referred Pain from Cardiac or Pulmonary Sources: Given the patient's age and history of smoking, although quit in 2014, it's crucial to consider cardiac or pulmonary causes of referred pain to the shoulder, such as myocardial infarction or pulmonary embolism. These conditions are life-threatening and must not be missed.
  • Infection or Septic Arthritis: Although the patient does not have fever or significant swelling, infection must always be considered, especially in the context of sudden onset of pain and a history of prior steroid injection, which could potentially increase the risk of infection.

• Rare Diagnoses

  • Neoplastic Processes: Tumors, either primary or metastatic, affecting the shoulder region could cause pain and limited mobility. Given the patient's history of hip replacements, the possibility of metastatic disease, although rare, should be considered.
  • Polymyalgia Rheumatica: This condition can cause shoulder pain and stiffness, particularly in older adults. However, the absence of systemic symptoms such as fever and the lack of significant morning stiffness make this diagnosis less likely.
  • Brachial Plexitis (Neuralgic Amyotrophy): Characterized by severe shoulder and arm pain followed by weakness, this condition is rare but should be considered in the differential diagnosis of sudden onset shoulder pain.