• Shoulder pain in the posterior boarder is often from cervical spine (Neck Pain) • Shoulder joint pain is often felt in the upper arm

Rule out Inflammation arthritis, infection, fracture → Refer to Arthritis
Rule out malignancy → Constitutional symptom , XR, MRI
Rule out referred or radiating pain

DDx of MSK Pain based on Anatomy
MRI if suspect:
Joint XR OA Finding if suspect: