Differential Diagnosis for Intermittent Right Shoulder Throbbing Pain

Single Most Likely Diagnosis

• Subacromial Bursitis or Rotator Cuff Tendinitis: This is the most likely diagnosis given the patient's history of heavy lifting, which can cause inflammation of the bursae or tendons in the shoulder, leading to pain that worsens with movement. The patient's report of pain with palpation over the lateral aspect of the shoulder and full range of motion (ROM) despite pain also supports this diagnosis.

Other Likely Diagnoses

• Strain of the Shoulder Muscles: Heavy lifting can cause strain to the muscles of the shoulder, leading to pain and discomfort, especially with movement.
• Adhesive Capsulitis (Frozen Shoulder): Although less likely given the patient's full ROM, early stages of adhesive capsulitis could present with pain and stiffness, especially after periods of increased activity or trauma.
• Labral Tear: A labral tear could be considered, especially if the patient had experienced any traumatic event or has a history of shoulder instability, though the patient denies any injury.

Do Not Miss Diagnoses

• Fracture: Although the patient denies an injury, it's crucial to consider the possibility of a fracture, especially a stress fracture, which might not have been immediately recognized. A fracture could lead to severe complications if not properly diagnosed and treated.
• Infection (Septic Arthritis or Osteomyelitis): Infection in the shoulder joint or bone could present with pain and limited mobility due to pain, and it is critical to identify and treat promptly to avoid serious complications.
• Referred Pain from the Cervical Spine: Pain referred from the cervical spine, such as from a herniated disc or cervical spondylosis, could mimic shoulder pain and must be considered, especially if there are any neurological symptoms.

Rare Diagnoses

• Polymyalgia Rheumatica: This condition involves inflammation of the muscles, leading to pain and stiffness, typically in the shoulders and hips. It's less common but should be considered in the differential diagnosis, especially in older adults.
• Neoplastic Processes: Although rare, tumors (either primary or metastatic) could cause shoulder pain and must be considered, especially if the pain is persistent and unexplained by other causes.