Can you interpret the imaging studies for a 67‑year‑old female with left shoulder pain and intermittent popping, worsened by turning while driving, with no recent trauma, weakness, radiation, or prior injury?

Imaging Interpretation for Shoulder Pain in Primary Care

Yes, as a primary care physician you can and should interpret shoulder imaging, starting with plain radiographs as the initial study, followed by MRI or ultrasound if radiographs are normal or nonspecific and clinical suspicion for rotator cuff or labral pathology remains. 1

Initial Imaging Approach

Begin with plain radiographs of the left shoulder in at least two views (AP and lateral or scapular Y). This is the universally appropriate first imaging study for any shoulder pain presentation, regardless of suspected etiology 1. Radiographs will:

• Rule out fractures (especially important given the patient's age and risk of occult injury)
• Identify glenohumeral or acromioclavicular joint arthritis
• Detect calcific tendinopathy
• Show any bony abnormalities or degenerative changes

Interpreting Your Clinical Scenario

This 67-year-old woman presents with features suggesting rotator cuff pathology with possible instability:

• Pain with turning while driving suggests rotator cuff tendinopathy or impingement
• Intermittent popping with sensation of dropping objects raises concern for either:
  • Rotator cuff tear (particularly if there's subluxation of the humeral head)
  • Labral pathology with instability
  • Subacromial impingement with catching

The absence of trauma doesn't exclude significant pathology—age-related degenerative rotator cuff tears are extremely common in this demographic, with full-thickness tears occurring in 50-80% of older adults 2. The correlation between age and rotator cuff derangement is highly significant 3.

Next Steps After Radiographs

If Radiographs Are Normal or Nonspecific:

Order MRI shoulder without IV contrast as the next study 1. This is the preferred modality because:

• It provides comprehensive evaluation of rotator cuff, labrum, and capsular structures
• Has 96.5% sensitivity for rotator cuff tears overall and 100% sensitivity for full-thickness tears 4
• Can identify bone marrow edema, subacromial bursitis, and labral pathology
• Superior for detecting intra-articular pathology compared to ultrasound

Alternative: Shoulder ultrasound is also appropriate and has equivalent performance for full-thickness rotator cuff tears (90-91% sensitivity, 93-95% specificity) 1, 4. However, MRI is preferred in this case because:

• The popping sensation suggests possible labral or instability issues, which ultrasound cannot adequately assess
• MRI better evaluates partial-thickness tears
• Patient's age makes multiple pathologies likely (AC joint degeneration, subacromial bursitis, rotator cuff disease) 3

Specific Findings to Look For on MRI:

1. Rotator cuff integrity: Full-thickness vs. partial-thickness tears, particularly supraspinatus
2. Subacromial-subdeltoid bursal fluid/inflammation: Present in 86% of symptomatic patients 3
3. Labral tears: Especially superior labrum given the popping sensation
4. AC joint degeneration: Highly prevalent in this age group (62% in symptomatic patients) 3
5. Glenohumeral joint effusion or cartilage loss
6. Biceps tendon pathology

Common Pitfalls to Avoid

• Don't skip radiographs: Even without trauma history, occult fractures and degenerative changes need exclusion first
• Don't order MRI with contrast initially: In acute/subacute presentations, joint effusion provides natural contrast 1. MR arthrography is reserved for chronic cases or when initial MRI is indeterminate
• Don't assume typing caused this: While repetitive activity contributes to rotator cuff disease, the acute onset upon waking and popping sensation suggest structural pathology requiring imaging
• Don't rely solely on lack of weakness: Patients can have significant rotator cuff tears without obvious weakness, especially if compensatory muscles are intact

Your Role as PCP in Interpretation

You should be comfortable interpreting:

• Radiographs: Fractures, dislocations, arthritis, calcifications
• Basic MRI findings: Full-thickness rotator cuff tears, large effusions, obvious labral tears
• Ultrasound (if you perform point-of-care): Full-thickness rotator cuff tears

Refer to radiology for formal interpretation but use your clinical correlation to guide management. If imaging shows significant pathology (full-thickness rotator cuff tear, labral tear with instability), orthopedic referral is appropriate. Conservative management with physical therapy is reasonable for partial tears, tendinopathy, or impingement without mechanical symptoms.