The Caton-Deschamps Index is a measure of the position of the patella relative to the tibia.

caton-deschamps index
It is not always easy to decide the exact points of the lines because the patella is slightly different in shape in each person.


Caton-Deschamps Index and patella alta

The index is of value in determining whether or not there is patella alta (high riding kneeap). It is a ratio of the distance between:

  • the lower point of the part of the patella that makes contact with the femur to the top of the tibial plateau
  • the length of the part of the back of the patella that makes contact with the femur 

The normal range is 0.8-1.2. A ratio higher than 1.3 is suggestive of patella alta.


The unstable patella

A discussion about patellar instability, the factors that may cause the patella to sublux or dislocate, and what can be done about it.



Evaluation of patella alta using MRI measurements in adolescents. Yılmaz B, Ozdemir G, Sirin E, Cicek ED, Anıl BS and Bulbun G. Indian J Radiol Imaging. 2017 Apr-Jun; 27(2): 181–186.

See also -


eBook on patellar instability

eBook - Factors contributing to an Unstable Patella

An easy-to-read eBook about patella alta and other causes of kneecap instability.