Patellofemoral dysplasia is assessed on a number of criteria:
The 3 main ones are:
• Patellar Alta: patella ratio > 1.5
• Increased TTTG greater than 20mm
• Shallow femoral groove less than 3mm
Other criteria include:
For PTR, some use a ratio of >1.3 however this is rather non specific
The TTTG is the equivalent of the clinical Q angle
Other criteria are used including
• Lateral trochlear inclination
• Patellar angle
•Patellar shape
•Trochlear facet assymmetry
•Lateral patellar tilt and translation
The term 'Maltracking' has come into common usage when the above parameters are abnormal. In the past, the term was reserved for when actual abnormal lateral movement (deviation or tilt) were demonstrated on dynamic studies.
Oedema in the superolateral corner of Hoffa's fat pad is associated with patellofemoral dysplasia and its presence used to diagnose 'maltracking'. NOt all patients with Hoffa's oedema are symptomatic.
HOW TO MEASURE
TTTG
Clinically the Q angle is assess from 3 points: the ASIS, Patellar centre and tubercle
The TTTG uses a distance measurement
Place the cursor on the groove at its deepest point
Scroll down to the tibial tubercle
Draw a line between the cursor and the middle of the tubercle
This distance is the TTTG
PTR
The ratio of the length of the patellar tendon to the longest long axis of the patella
