Differential Diagnosis

• Single most likely diagnosis
  • Shoulder Impingement Syndrome: This is the most likely diagnosis given the narrowing of the subacromial space, which is a common finding in impingement syndrome. The degenerative changes in the shoulder joint and AC joint, as well as the cystic changes in the humeral head, also support this diagnosis.
• Other Likely diagnoses
  • Rotator Cuff Tendinosis: The presence of degenerative changes in the shoulder joint and AC joint, along with the narrowing of the subacromial space, could also suggest rotator cuff tendinosis.
  • Osteoarthritis of the Shoulder: The degenerative changes in the shoulder joint and AC joint, as well as the cystic changes in the humeral head, could be indicative of osteoarthritis.
• Do Not Miss
  • Rotator Cuff Tear: Although the soft tissue is described as unremarkable, a rotator cuff tear could still be present and would be a critical diagnosis to miss. Clinical correlation is necessary to rule out this possibility.
  • Septic Arthritis: Although there is no gross evidence of acute infection, septic arthritis could still be present and would require prompt treatment.
• Rare diagnoses
  • AVN (Avascular Necrosis) of the Humeral Head: The cystic changes in the humeral head could potentially be indicative of AVN, although this would be a less common diagnosis.
  • Bone Tumor: Although unlikely, a bone tumor could potentially cause the cystic changes in the humeral head and would require further investigation to rule out.