Caton-Deschamps index (knee)

Last revised by Jeremy Jones on 27 Jan 2024

The Caton-Deschamps index is used to measure patellar height and identify patella alta and patella baja. The Caton-Deschamps index relies upon the length of the patellar articular surface and its distance from the tibia, reducing erroneous measurements in those with long patella bodies, as measured in the Insall-Salvati ratio.


The Caton-Deschamps index can be measured on a lateral radiograph or sagittal knee CT or MRI. For measurement, it is considered ideal that the knee is flexed at an angle of 30º, although for the original study by Caton-Deschamps the flexion angles were between 20º and 80º.

  • A: distance between the anterior angle of the tibial plateau, to the most inferior aspect of the patellar articular surface
  • B: patellar articular surface length

Caton-Deschamps index = A / B


  • normal range: 0.6-1.3
  • patella alta: >1.3
  • patella baja: <0.6

The Caton-Deschamps ratio can also be applied to children, but age correction should be applied because patellar ossification begins at its proximal side 1.

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