1. This lower-leg image of a toddler shows a subtle fracture of the distal tibial shaft (arrow). The leg was placed diagonally across the detector. What is the MAIN reason for this placement?
Tibia & Fibula
The lower leg is the tibia (medial, weight-bearing) and fibula (lateral). A routine tib-fib is an AP and a lateral that include both the knee and the ankle.
Overview
Bones
Tibia
- Medial condyle
- Lateral condyle
- Intercondylar eminence
- Tibial tuberosity
- Shaft (anterior crest)
- Medial malleolus
Fibula
- Head
- Neck
- Shaft
- Lateral malleolus
Registry must-knows
- Include both joints. Place the IR diagonally or use two images if the leg is too long.
- Use the anode heel effect: cathode over the thicker knee end.
- Maisonneuve fracture: a proximal fibula fracture with a medial ankle injury, so image the whole leg after an ankle injury with medial tenderness.
- The tibia is the weight-bearing bone; the fibula carries little load.
3D model
Loading 3D…
Radiographs 2
Pick a film, then a structure to circle it.
Projections 2
Tap a projection for positioning, central ray and image criteria. See every exam in the Positioning Guide ›
AP tibia & fibula
CR: Perpendicular
- Position
- Supine, leg extended, femoral condyles parallel to the IR, foot dorsiflexed.
- Central ray
- Perpendicular
- Centering
- Mid-leg
- Typical technique
- 65–70 kVp · 4–8 mAs · 40–44" SID
Image criteria
- Knee and ankle joints both included.
- No rotation: femoral and tibial condyles symmetric.
- Slight overlap of the tibia and fibula at both ends.
Lateral tibia & fibula (mediolateral)
CR: Perpendicular
- Position
- Lateral recumbent on the affected side, knee flexed about 45°, femoral condyles superimposed.
- Central ray
- Perpendicular
- Centering
- Mid-leg
- Typical technique
- 65–70 kVp · 4–8 mAs · 40–44" SID
Image criteria
- Knee and ankle joints both included.
- Fibula partly superimposed by the tibia at both ends.
- Femoral condyles superimposed.
Technique values are typical starting points; follow your department's technique chart.
Labeled diagrams
Quick check
2. The red arrow points to the anatomic side marker on this tibia-fibula radiograph. Where should this marker be placed?
3. A 7-year-old has fever and a painful, swollen lower leg, and acute osteomyelitis of the distal tibia is suspected. Radiographs taken 2 days after symptoms began show no bone abnormality. What is the BEST explanation?
4. This lateral knee shows a fracture of the proximal fibular shaft in a patient who rolled the ankle. This combination, a Maisonneuve fracture, is associated with injury to which structures?
5. What three bones form the ankle mortise joint?