Grelsamer et al described the morphology ratio in a sagittal X-ray of the patella. This can help classify the patella's basic shape.
Examination: Sagittal radiograph of the patella in its midline
Measurement
Description
a
line from superior posterior point (top of articular surface) to inferior anterior point = overall patella length
b
length of articular surface, from superior to inferior posterior aspect
where:
• The a and b lines form 2 sides of a triangle. The third side is the inferior border of the patella, from the posterior inferior aspect of the articular surface to the anterior inferior aspect.
morphology index =
= (length of a) / (length of b)
Morphology Index
Patella Type
< 1.2
Type III
1.2 to 1.5
Type I
> 1.5
Type II
To read more or access our algorithms and calculators, please log in or register.
