What is the initial imaging recommendation to differentiate between osteoarthritis (OA) and rotator cuff injury in a patient with left shoulder pain?

Radiographic Evaluation to Differentiate Shoulder OA from Rotator Cuff Injury

Standard radiography is the preferred initial imaging study for differentiating between osteoarthritis and rotator cuff injury in a patient with left shoulder pain. 1

Initial Radiographic Assessment

• A complete shoulder radiographic series should include anteroposterior (AP) views in both internal and external rotation, plus an axillary or scapular Y view, performed with the patient in an upright position 1
• Radiographs should be performed upright because malalignment of the shoulder can be underrepresented on supine radiography 1, 2
• Special projections may be added based on clinical suspicion:
  • Rockwood view for evaluation of shoulder impingement 1
  • Grashey view (true AP) to better visualize the glenohumeral joint space 3

Radiographic Findings

• For osteoarthritis, look for:
  • Joint space narrowing (particularly in the central anteroposterior and axillary views) 4
  • Osteophyte formation (especially at the inferior humeral head) 4
  • Subchondral sclerosis and cysts 3
• For rotator cuff pathology, look for:
  • Superior migration of the humeral head (indirect sign of rotator cuff tear) 1
  • Acromiohumeral interval narrowing (<7mm suggests rotator cuff tear) 3
  • Sclerosis of the greater tuberosity 3

Advanced Imaging When Radiographs Are Noncontributory

If radiographs are normal or noncontributory but clinical suspicion remains high:

• For suspected rotator cuff tear:

  • MRI shoulder without IV contrast (rating 9/9) or ultrasound of the shoulder (rating 9/9) are equally appropriate next steps 1
  • These procedures are equivalent alternatives and only one study needs to be ordered 1

• For suspected osteoarthritis with normal radiographs:

  • MRI shoulder without IV contrast is usually appropriate (rating 7-9/9) 1

Choosing Between MRI and Ultrasound for Rotator Cuff Assessment

• MRI is preferred when:

  • Patient has large body habitus 1
  • Patient has restricted range of motion due to acute pain 1
  • There is suspicion of other intra-articular pathologies (such as labral tears) 1
  • A comprehensive evaluation of bone marrow, cartilage, and deep structures is needed 1

• Ultrasound is preferred when:

  • There is previously placed proximal humeral hardware that would create MRI artifacts 1
  • Rapid, dynamic assessment is desired 5
  • Cost is a significant concern 5
  • MRI is contraindicated 1

Common Pitfalls to Avoid

• Inadequate imaging leading to missed diagnoses - ensure proper views are obtained 2
• Relying solely on AP views - acromioclavicular and glenohumeral pathologies can be misclassified without axillary or scapular Y views 6
• Over-reliance on radiographic findings alone - joint space narrowing does not always correlate with pain levels in osteoarthritis 4
• Failure to recognize that osteophyte size, rather than joint space narrowing, may better correlate with functional limitations in shoulder OA 4