Background: The femoral trochlea is considered the most significant osseous factor affecting stability in the patellofemoral joint. The true prevalence of trochlear dysplasia in the general population is largely unknown. Purpose/Hypothesis: To investigate the prevalence of trochlear dysplasia in the general population. Our hypothesis was that, while trochlear dysplasia is not uncommon, there is a low prevalence of severe dysplasia in the general population. Study Design: Descriptive epidemiology study. Methods: Five observers were asked to evaluate 692 skeletally mature femoral specimens from 359 skeletons for trochlear dysplasia at 2 time points. We further subclassified the dysplastic trochlea in 62 femora with the highest rated degree of dysplasia. Results: Sex ( P = .11) and race ( P = .2) had no effect on the severity of dysplasia. Interobserver reliability was excellent (0.906 and 0.904), and intraobserver reliability was good to excellent (0.686 to 0.808). The percentages of trochlea graded as normal, mildly dysplastic, moderately dysplastic, and severely dysplastic were 61.5%, 21.4%, 12.7%, and 4.4%, respectively, in the first evaluation, and 58.5%, 23.7%, 12.7%, and 5.1% in the second evaluation. Of the 62 trochlea with the highest scores for dysplasia, 36 had trochlear dysplasia without a supratrochlear spur, 8 had trochlear dysplasia with medial femoral condyle hypoplasia, and 18 had trochlear dysplasia with a supratrochlear spur. Conclusion: Observers with differing degrees of clinical experience had similar opinions on the degree of trochlear dysplasia. Also, our cohort showed that moderate to severe dysplasia is not uncommon, as it is present in approximately 17% of knees in our cohort. Our findings also suggest that clinicians are speaking the same language when identifying and describing trochlear dysplasia on gross inspection.
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