Stanford MSK Atlas of MSK Measurements

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DEFINITION:
bony method: (1) line tangent to the posterior epicondyle (red), (2) perpendicular line through deepest point of the trochlea (blue), (3) line parallel to the trochlea line through the most anterior portion of the tibial tuberosity (green); TT-TG measurement is distance btwn blue & green lines.

ABNORMAL:
if > 20 mm then shows valgus component of extensor mechanism of knee; asso w/ patellar instability & trochlear dysplasia

RADLEX:
patella ( RID2746 )

how to draw the tibial tuberosity trochlear groove distance