Patellofemoral malalignment and lateral patellar cartilage degeneration in adults with an Osgood–Schlatter-compatible MRI phenotype

Background Residual tibial tubercle morphology compatible with previous Osgood–Schlatter disease (OSD) may coexist with patellofemoral malalignment; however, its relationship with patellar cartilage damage is unclear. Purpose To compare magnetic resonance imaging (MRI)-based patellofemoral morphology between adults with and without an OSD-compatible MRI phenotype and evaluate imaging factors associated with lateral patellar cartilage degeneration. Material and Methods This retrospective study included 199 adults (209 knees) with an OSD-compatible MRI phenotype and 238 age- and sex-frequency-matched symptomatic comparison participants. Patellofemoral measurements and lateral patellar cartilage were assessed on 1.5-T MRI. A patient-clustered parsimonious generalized estimating equation model included age, sulcus angle, patellar tilt, and Insall–Salvati index; performance was evaluated by patient-level bootstrap. Results OSD-compatible knees showed greater patellofemoral malalignment and more frequent lateral patellar cartilage degeneration than symptomatic comparison knees (47.8% vs. 10.1%; P < 0.001). Older age (adjusted odds ratio (OR) = 1.12 per year, 95% confidence interval (CI) = 1.08–1.16), larger sulcus angle (OR = 1.07 per degree, 95% CI = 1.01–1.13), greater patellar tilt (OR = 1.19 per degree, 95% CI = 1.09–1.30), and higher Insall–Salvati index (OR = 1.64 per 0.10 increase, 95% CI = 1.11–2.44) were associated with chondromalacia. Apparent and optimism-corrected areas under the receiver operating characteristic curve were 0.893 and 0.884, respectively. Conclusion Adults with an OSD-compatible MRI phenotype had more patellofemoral malalignment and lateral patellar cartilage degeneration than symptomatic comparison participants. The cross-sectional design and unmeasured confounding limit causal and population-level inference.