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Previous studies have attempted to characterize patellar morphology and its relation to patellofemoral osteoarthritis but have utilized relatively small samples. We designed a large-scale cadaveric analysis to elucidate any potential relationship. Patellar morphology in 1,032 patellae was characterized using patellar facet concavity patterns initially developed by Wiberg and using the ratio of the lateral and medial facet lengths. Patellofemoral arthritis grading for specimens was previously completed based primarily on osteophytic burden. The average age at time of death was 56 ± 10 years. Wiberg's grading returned kappa values of 0.43 for intrarelator reliability and 0.27 for interrelator reliability. Using multiple regression analysis, Wiberg's type II was found to be correlated with patellofemoral arthritis (p = 0.003). Lateral to medial facet ratio measurements returned intraclass coefficients of 0.91 for intrarelator reliability and 0.85 for interrelator reliability. There was no association between lateral to medial facet ratio and osteoarthritis. Regression analysis between Wiberg's typing and lateral-to-medial ratio (L:M) resulted in a coefficient of determination of 0.14. To our knowledge, this is the largest study evaluating the relationship between patellar morphology and arthritis. Although there was a relationship between Wiberg's type II and patellofemoral arthritis, the Wiberg systems was not easily reproducible in our study and returned a correlation with arthritis different then anatomically expected. A more reproducible system of lateral to medial facet ratio was investigated but did not find an association with arthritic changes. Given these findings, we did not find a patella morphology grading system which is both reliable and valid in regard to association with patellofemoral arthritis.

Disorders of the patellofemoral joint are common. Diagnosis and management often involves the use tangential imaging of the patella and trochlear grove, with the sunrise projection being the most common. However, imaging protocols vary between institutions, and limited data exist to determine which radiographic projections provide optimal visualization of the trochlear groove at its deepest point. Plain radiographs of 48 cadaveric femora were taken at various beam-femur angles and the maximum trochlear depth was measured; a tilt-board apparatus was used to elevate the femur in 5-degree increments between 40 and 75 degrees. A corollary experiment was undertaken to investigate beam-femur angles osteologically: digital representations of each bone were created with a MicroScribe digitizer, and trochlear depth was measured on all specimens at beam-femur angles from 0 to 75 degrees. The results of the radiographic and digitizer experiments showed that the maximum trochlear grove depth occurred at a beam-femur angle of 50 degrees. These results suggest that the optimal beam-femur angle for visualizing maximum trochlear depth is 50 degrees. This is significantly lower than the beam-femur angle of 90 degrees typically used in the sunrise projection. Clinicians evaluating trochlear depth on sunrise projections may be underestimating maximal depth and evaluating a nonarticulating portion of the femur.