Differential Diagnosis

• Single most likely diagnosis
  • Calcific tendinitis: This diagnosis is most likely due to the presence of punctate calcific densities in the subacromial space, which is a characteristic finding of calcific tendinitis. The relative narrowing of the subacromial space and degenerative changes in the shoulder joint and AC joint also support this diagnosis.
• Other Likely diagnoses
  • Shoulder impingement syndrome: The relative narrowing of the subacromial space and degenerative changes in the shoulder joint and AC joint make shoulder impingement syndrome a likely diagnosis. Clinical correlation is recommended to confirm this diagnosis.
  • Osteoarthritis of the shoulder joint: The degenerative changes in the glenoid rim and AC joint suggest osteoarthritis of the shoulder joint, which is a common condition that can cause similar symptoms.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Septic arthritis: Although the soft tissue is unremarkable, septic arthritis is a potentially life-threatening condition that should not be missed. It can present with similar symptoms and imaging findings, and clinical correlation is necessary to rule out this diagnosis.
  • Fracture: Although there is no gross evidence of acute displaced fracture, a fracture should not be missed. Clinical correlation and further imaging may be necessary to rule out a fracture.
• Rare diagnoses
  • Rheumatoid arthritis: This is a rare diagnosis that can cause similar symptoms and imaging findings. However, the absence of significant soft tissue swelling and the presence of degenerative changes make this diagnosis less likely.
  • Tumors: Tumors such as osteochondroma or chondrosarcoma can cause similar symptoms and imaging findings. However, these diagnoses are rare and would require further imaging and clinical correlation to confirm.