Radiographic parameters associated with lateral patella degeneration in young patients

Purpose: Localized articular cartilage degeneration in the patellofemoral joint is a common but yet understudied condition in younger patients. The purpose of this paper was to determine whether there are significant differences in radiographic alignment between those with and without isolated lateral patellofemoral degeneration. Methods: Subjects with isolated symptomatic lateral patellofemoral degeneration and control subjects with no radiographic degeneration participated in the study. Variables of interest included the Caton-Deschamps index, sulcus angle, lateral patellofemoral angle, Dejour classification of trochlear dysplasia, patella linear displacement and the tibial tubercle-trochlear groove distance. Results: We found significant differences between the patellofemoral degeneration group versus control group, respectively, for the Caton-Deschamps index (1.12 ± 0.1 vs. 1.00 ± 0.1), lateral patellofemoral angle (10.6 ± 4.3 vs. 16.6 ± 5.5) and tibial tubercle-trochlear groove distance (16.6 ± 4.0 vs. 9.0 ± 4.3). However, we found no difference in the sulcus angle (141.2 ± 8.2 vs. 137.0 ± 6.0), patella linear displacement (3.7 ± 1.9 vs. 4.0 ± 1.7) or in the Dejour Classification. Conclusion: It appears that isolated lateral patellofemoral degeneration is associated with specific radiographic indices. Even though the radiographic measures in patients with degeneration may not be considered pathologic, they are "high normal" and may represent a risk factor for the development of focal chondral degeneration in the lateral trochlea and patella. Level of evidence: III.