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Anatomy of Patella

- Discussion:
    - sesamoid bone w/ in quadriceps tendon;
    - cartilaginous posterior surface is divided by a rounded vertical ridge into a larger, lateral portion for articulation w/ lateral condyle of femur and smaller
           medial portion for articulation w/ medial condyle of femur;
    - w/ increasing knee flexion, contact pressure moves proximally on patella up to superior pole and onto quadriceps tendon;
    - articular surface of patella, varying in thickness from approximately 2 to 5.5 mm, is divided into 7 fascets;
           - medial and lateral facets are divided into = 1/3 sections;
           - superiorly and inferiorly, with the 7th facet being the most medial portion called the odd facet;
    - Wiberg: 3 shapes based on position of vertical ridge;
           - type I:  there are roughly = medial and lateral facets
           - type II  most common: medial facet is only 1/2 size of lat. facet;
           - type III medial facet is so far medial that the central ridge is barely noticable;

- Blood Supply:
    - blood supply to patella originates from as many as 12 nutrient arteries at the inferior pole,
           which run upward on the anterior surface of the bone in a series of furrows;
    - may arise from mid patellar vessels penetrating middle 1/3 of anterior surface & inferior pole vessels that anastomose at inferior pole of patella;
    - geniculate system feeds these primary vessels;
           - anterior tibial recurrent vessels
           - inferior medial genicular
           - inferior lateral genicular
    - references:
           - Quantitative and qualitative assessment of bone perfusion and arterial contributions in a patellar fracture model using gadolinium-enhanced magnetic resonance imaging: a cadaveric study.
Vascular anatomy of the patella: implications for total knee arthroplasty surgical approaches.
Safe zone for the descending genicular artery in the midvastus approach to the knee.