1. Chondromalacia of the patella starts most frequently on the medial facet.
2. The anatomy of the medial femoral condyle is described, including the rim at its superior border, and the different arrangement at the upper border of the lateral femoral condyle.
3. Rubbing of the medial patellar facet on the rim at the upper border of the medial femoral condyle can explain in part the etiology of chondromalacia.