Study design: Descriptive.
Objective: Describe and compare patellar and femoral condylar wear patterns, and the wear frequency of both, relative to each other, gender, and sidedness.
Background: Studies on normal and pathological patellar cartilage and patellofemoral joint biomechanics are plentiful. However, patellar wear patterns are undefined, as is the relationship of patellar to femoral condylar wear.
Methods: Articular wear was described for 50 patellae and matching femurs from 26 cadavers. Wear locations were transcribed to gridded templates, and these were compared graphically for frequency, gender, and sidedness of wear. The percent frequency of wear was calculated and areas of wear described.
Results: Three patellar and 2 femoral types of wear patterns were observed, and 12 areas of patellar wear and 3 areas of femoral wear described. Patella wear was along the horizontal middle of the patella, with marked medial and odd facet wear. Femoral wear was on the anterior and posterior aspects of the medial condyle, and posterior aspect of the lateral femoral condyle. Patellar and femoral wear frequencies were similar bilaterally, but patellar wear may differ with gender.
Conclusions: Patella and distal femur showed distinct wear patterns. The wear area under the patella matches the contact area between the patella and distal femur normally occurring between 45 degrees to 90 degrees of knee flexion. Patellofemoral assessment and treatment may differ for the aged population because of mechanical changes due to wear.