Radiographic Evaluation of the Foot & Ankle

1. General Principles

• Weight-bearing radiographs should be obtained whenever possible.

• Standard ankle views:

  • AP

  • Lateral

  • Mortise view (15° internal rotation → clear visualization of ankle joint space)

• Standard foot views:

  • AP

  • Lateral

  • Oblique (medial/lateral column evaluation)

• Stress views (gravity/manual) are useful for:

  • Syndesmotic injuries (SER, Weber B/C)

  • Deltoid ligament competence

  • Ankle instability (anterior drawer, varus/valgus tilt)

2. Key Ankle Measurements

A. Medial Clear Space (MCS)

• Normal: ≤ 4 mm and symmetric to superior clear space.

• Widening > 5 mm on stress radiographs → deltoid ligament rupture.

• Gravity stress views may substitute for manual stress

B. Tibiofibular Clear Space (TFCS)

• Measured 1 cm above tibial plafond.

• Normal: < 6 mm.

• Increased values → syndesmotic injury.

C. Tibiofibular Overlap (TFO)

• AP view:

  • Normal: > 6 mm.

• Mortise view:

  • Normal: > 1 mm.

• Decrease indicates syndesmotic disruption.

D. Talar Tilt (Varus/Valgus Tilt)

• Measures lateral ligament integrity.

• Difference in talar tilt between stressed and unstressed views:

  • 10° or asymmetry → ATFL/CFL insufficiency.

E. Anterior Talar Translation (Anterior Drawer View)

• Lateral fluoroscopic stress view.

• Normal translation: < 4 mm.

• Increased translation indicates ATFL insufficiency.

F. Mortise Alignment

• Symmetrical joint space around talus.

• Check for:

  • Widened medial gutter

  • Obliteration of lateral gutter

• Important for detecting Weber B/C & SER injuries.

3. Key Foot Measurements

A. Meary’s Angle (Talo-First Metatarsal Angle)

Lateral view.

• Normal: 0° (talar axis aligns with 1st MT axis).

• Positive apex plantar: Pes planus.

• Positive apex dorsal: Pes cavus.

B. Calcaneal Pitch

• Lateral view.

• Normal: 17–32°.

• Increased: Cavus foot.

• Decreased: Planovalgus.

C. Hindfoot Alignment Angle

• Saltzman view preferred.

• Measures calcaneal axis relative to tibial axis.

• Varus/valgus deformity quantification.

D. Talo-Calcaneal Angle (Kite Angle)

• AP view.

• Normal: 20–40°.

• Decreased: Clubfoot.

• Increased: Flatfoot.

E. Talo-First Metatarsal Angle (Simmon Angle) (AP)

• Normal: 0–20°.

• Deviations indicate forefoot abduction/adduction deformity.

F. First Metatarsal–Cuneiform Angle

• Used for hallux valgus analysis.

4. Special Radiographic Views

5. Stress Tests On Radiographs & Their Interpretation

A. Gravity Stress View (SER or Weber B injury)

• Increased MCS (>4–5 mm) = deep deltoid failure.

B. Varus Stress View

• Assess ATFL/CFL integrity.

• 10° tilt = lateral instability.

C. Anterior Drawer Stress

• Increased anterior translation = ATFL insufficiency

6. When to Use Advanced Imaging

CT

• Talar neck fractures

• Calcaneus fractures

• Lisfranc injuries

• Coalition evaluation

MRI

• Osteochondral lesions

• Tendon pathology

• Soft tissue injuries (deltoid, syndesmotic ligaments)

• Stress reactions/fractures

Bone Scan / WBC Scan

• Stress fractures

• Suspected osteomyelitis