The adult knee

​When are knee films indicated?

• Trauma
• Bony tenderness at the head of the fibula
• Isolated patella tenderness
• Patient unable to flex the knee to 90 degrees
• If the patient is unable to weight bear
• Suspected osteoarthritis
• Detecting joint effusions
• Infection

Standard Views:

• AP View

• Lateral Horizontal Beam

• Skyline View

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Systematic Approach to Adult Knee Films:
1) Know your anatomy!

​2) Check for an effusion

3) Check the main bones (tibia, femur, fibular head, and patella)

4) Check the tibio-femoral alignment -- The tibia should be within 0.5 cm of this line, otherwise it suggests a lateral tibial plateau fracture.

​▪ 5) Look at the tibial plateaus -- Fractures most commonly happen on the lateral tibial plateau
*Check for a tibial plateau avulsion from the lateral edge (Segond fracture)

6) Look for patellar tendon disruption
  - In a normal knee, the ratio is between 0.8 - 1.2 (mean value = 1)

• If the ratio is < 0.8, the patella lies low (=patella baja)
• If the ratio is > 1.2, the patella lies high (=patella alta)

7) Don’t forget the fabella! It’s a normal sesamoid bone of the lateral head of gastrocnemius tendon - NOT to be mistaken for a fracture or loose body

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Resources and Images:
https://radiopaedia.org/articles/knee-series
https://radiopaedia.org/articles/knee-radiograph-an-approach
http://dontforgetthebubbles.com/knee-x-ray-interpretation/
http://www.radiologymasterclass.co.uk/tutorials/musculoskeletal/x-ray_trauma_lower_limb/knee_x-ray
http://www.imageinterpretation.co.uk/knee.php

By: Dr. jeremy driscoll M.D.