Patellar instability

Case contributed by Dr Ayush Goel


Recurrent bilateral patellar dislocation.

Patient Data

Age: 30 years
Gender: Female

Tibial tuberosity (TT) to trochlear groove (TG)  distances:

  • right knee TT-TG = 24.3mm
  • left knee TT-TG = 19.6mm


Case Discussion

Distance from tibial tuberosity to trochlear groove (TT-TG) is one of the best measure for patellar instability.


  • normal : <15 mm
  • borderline : 15-20 mm
  • abnormal : >20 mm
PlayAdd to Share

Case information

rID: 28749
Published: 10th Apr 2014
Last edited: 14th Feb 2019
Inclusion in quiz mode: Included

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.