A 64-year-old is experiencing chronic pain and weakness in his dominant arm and shoulder for the previous 2 months, with no previous trauma. He has minor pain on palpation of the right shoulder. His pain is increased with arm abduction of more than 90° and has weakness with external rotation of the arm. He cannot maintain his arm in an elevated position for more than a few seconds. An injection of local anesthetic relieves his pain but does not help with the weakness.

Required:

a) Explain the possible anatomical causes for each of these symptoms and identify the anatomical structures likely to be involved.

b) Identify three differential diagnoses (diseases or conditions that present similar signs and symptoms that could possibly account for the student’s symptoms) with appropriate justifications. Provide the most likely diagnosis based on this analysis.

c) Explain the various treatment options for the presenting symptoms.