Interpreting Musculoskeletal Imaging

1. What body part and laterality? (Default: Verify from order — laterality errors are sentinel events)
2. What modality? (Default: Radiograph — specify CT, MRI, or US)
3. What is the clinical indication? (Default: Trauma, pain, post-operative — obtain specific mechanism)
4. Is this a trauma or non-trauma study? (Default: Trauma — determines classification system)
5. Are prior studies available? (Default: No priors)
6. Is the patient pediatric (<18)? (Default: Adult — pediatric requires growth-plate assessment)
7. Is this a post-operative evaluation? (Default: No — if yes, obtain operative note)
8. Are weight-bearing views obtained (if applicable)? (Default: Verify for knee, ankle, foot)

Documents to Request

• Current imaging study (all views/sequences)
• Prior imaging of the same body part
• Requisition with mechanism of injury and clinical question
• Operative notes if post-surgical evaluation
• Relevant clinical exam findings (instability, point tenderness, ROM)
• For MRI: prior arthroscopy or surgical reports

Step 1: Radiograph Interpretation — Systematic Approach

Use the "ABCDs" mnemonic for every MSK radiograph:

A — Alignment

• Joint congruency and articular surface relationships
• Angular deformity (varus/valgus, anterior/posterior angulation)
• Displacement measurement (mm and percentage of bone width)
• Subluxation or dislocation

B — Bone

• Cortical integrity: fracture lines (transverse, oblique, spiral, comminuted)
• Bone density: osteopenia, lytic lesions, blastic lesions
• Periosteal reaction: solid, lamellated, sunburst, Codman triangle
• Bone infarcts, enchondromas, fibrous cortical defects

C — Cartilage and Joint Space

• Joint space narrowing (uniform vs. non-uniform)
• Osteophyte formation
• Subchondral sclerosis and cysts
• Chondrocalcinosis

D — Soft Tissues

• Joint effusion (fat pad signs: sail sign in elbow, suprapatellar)
• Soft-tissue swelling localization
• Foreign bodies
• Calcific tendinopathy, myositis ossificans

Step 2: Fracture Classification Systems

Upper Extremity

Lower Extremity

Spine

Step 3: MRI Internal Derangement — Joint-Specific Protocols

Knee MRI Systematic Review

Shoulder MRI Systematic Review

Step 4: Report Structure

Findings Section Organization

1. Alignment — joint congruency, fracture displacement
2. Osseous structures — fractures with classification, marrow signal
3. Ligaments/Tendons — integrity, grading
4. Menisci/Labrum — tear type, location
5. Cartilage — grade, location, extent
6. Soft tissues — effusion, bursitis, masses
7. Hardware (if post-op) — position, loosening, periprosthetic fracture

Impression

• Numbered, most clinically significant first
• Fracture classification stated (e.g., "Weber B fibula fracture with deltoid ligament injury")
• Surgical relevance of findings highlighted
• Follow-up recommendations with modality and timing

Step 5: Pediatric-Specific MSK Considerations

Checkpoint B: Post-Draft Alignment (Mandatory)

1. Is laterality correctly stated and verified against the order?
2. Are fractures classified using the appropriate surgeon-expected system?
3. Is displacement quantified (mm and percentage)?
4. Are MRI ligament/tendon findings graded?
5. Are critical findings (e.g., NAT patterns in pediatrics) flagged for communication?

Quality Audit

• Laterality is explicitly stated and matches the requisition
• All views/sequences are systematically reviewed (ABCDs for radiographs)
• Fractures are classified using the appropriate named system
• Displacement and angulation are quantified
• Joint alignment is assessed
• MRI internal derangement uses validated grading systems
• Meniscal tears are graded (only Grade 3 = surgical tear)
• Rotator cuff tears specify full vs. partial thickness and retraction
• Effusion and soft-tissue findings are documented
• Hardware position is assessed in post-operative studies
• Pediatric growth plates are evaluated when applicable
• Comparison with prior studies documents interval change
• Critical findings (NAT, vascular injury, compartment syndrome) trigger immediate communication
• Impression includes surgical relevance of findings

Guidelines

1. Always verify laterality before interpretation — laterality errors are reportable sentinel events.
2. Use the fracture classification system expected by the surgical subspecialty (e.g., Schatzker for tibial plateau, not just "comminuted fracture").
3. On knee MRI, only Grade 3 meniscal signal (reaching articular surface) represents a surgical tear — Grades 1 and 2 are intrameniscal degeneration.
4. For scaphoid fractures, if radiographs are negative but clinical suspicion is high, recommend MRI within 24–48 hours per ACR Appropriateness Criteria.
5. In pediatric trauma, always assess the growth plates (Salter-Harris classification) and compare with the contralateral side when available.
6. Document the mechanism of injury when available — it directs attention to commonly associated injuries (e.g., dashboard injury → posterior hip dislocation + posterior wall acetabular fracture).
7. Post-operative imaging requires comparison with immediate post-op films to assess hardware migration, loosening, or periprosthetic fracture.
8. Suspect non-accidental trauma in children with metaphyseal corner fractures, posterior rib fractures, or fractures of different ages — this triggers mandatory reporting obligations.