Portner and Pakzad used the tibial plateau to patella angle (PPA) to judge the height of the patella. The authors are from the University of Ottawa.
Testing: lateral X-ray of the knee with knee flexed to 30 degrees
Parameters:
(1) line tangential to the subchondral bone of the medial tibial plateau
(2) point on this line at the posterior extent of the plateau
(3) line from this point to the inferior articular border of the patella
(4) angle subtended between these 2 lines.
Interpretation:
• Normal range: 21 to 29°
• An angle > 29° indicates patella alta.
• An angle < 21° indicates patella baja.
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Specialty: Surgery, orthopedic
