In the webinar below, Dr Joe Kang (radiology registrar) provides a structured approach to interpreting knee, ankle & foot x-rays, with an overview of common cases & pitfalls.

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Key Points

• Two Views to Exclude a Fracture: Always obtain two views to accurately exclude a fracture.
• Bone Alignment: Check the alignment of bones for any dislocation or misalignment.
• Cortex Examination: Examine the cortex for disruptions, steps, or abnormalities.
• Soft Tissue Observation: Look for signs of swelling or effusion indicating underlying fractures.

Knee X-Ray Views

• AP View (Anterior-Posterior): Standard front-to-back view.
• Horizontal Beam Lateral (HBL) View: Essential for detecting knee effusions, look for fat-fluid levels indicating lipohemarthrosis.
• Skyline View: Useful for identifying patellar fractures and joint alignment.

Fracture Examples in the Knee

1. Tibial Plateau Fracture:
   • Look for cortical disruption and changes in trabecular pattern.
   • Presence of lipohemarthrosis (fat-fluid level) indicates intra-articular fracture.
2. Patellar Fracture:
   • Typically more apparent on a skyline view.
   • Look for cortical discontinuity and alignment issues.
3. Fibular Head Fracture:
   • Often associated with tibial fractures, indicating high-energy trauma.

Ankle X-Ray Views

AP and Lateral Views: Standard views for assessing ankle injuries.

• Weber Classification:
  • Type A: Below the syndesmosis, often managed conservatively.
  • Type B: At the level of the syndesmosis, may require surgery.
  • Type C: Above the syndesmosis, usually unstable and requires surgical intervention.

Complex Fractures in the Ankle

1. Maisonneuve Fracture:
   • Proximal fibular fracture with associated ankle injury.
   • Requires imaging of both the knee and ankle.
   • Look for widening of the ankle mortise indicating ligamentous injury.
2. Polo Mint Principle:
   • A ring structure (tibia and fibula) typically breaks in two places.
   • If one fracture is identified, look for the second.

Foot X-Ray Views

AP, Oblique, and Lateral Views: Standard views for foot injuries. Ensure proper alignment of the bones.

Fracture Examples in the Foot

1. Stress Fractures:
   • Look for periosteal reaction and subtle lucencies.
   • Commonly affects the third and fourth metatarsals, often due to overuse.
2. Lisfranc Injury:
   • Disruption of the alignment in the midfoot.
   • On AP view, check alignment of the first metatarsal with the medial cuneiform.
   • On oblique view, check alignment of the second metatarsal with the middle cuneiform.
   • Widening of the joint spaces in the midfoot indicates instability.
3. Calcaneal Fracture:
   • Typically results from a fall landing on the feet.
   • Look for comminuted fractures and flattening of Böhler’s angle.
   • Bilateral calcaneal fractures suggest high-energy trauma; assess for spine and pelvis injuries.
4. Base of Fifth Metatarsal Fracture:
   • Commonly due to inversion injuries.
   • Check for avulsion fractures at the insertion of the peroneus brevis tendon.
5. Osteomyelitis:
   • Look for bone destruction and periosteal reaction.
   • Associated with soft tissue ulcers and infections, common in diabetic patients.
   • Follow-up films or MRI may be necessary for early detection.