Adverse patellofemoral morphology and worsening osteoarthritis: an exploration of composite vs. single MRI outcomes

To evaluate whether a composite outcome measure could better detect the effects of adverse patellofemoral morphology on knee structure over two-years than single outcome measures. We used data from the Multicenter Osteoarthritis Study (MOST) to analyze the association between measures of patellofemoral morphology and composite outcomes that combined data on cartilage damage and bone marrow lesion enlargement in two subregions of the patellofemoral joint using proportional odds regression to account for ordinality. We used Z scores to assess sensitivity to change. In the cohort of 240 MOST participants with a mean age of 51 years, BMI of 29 kg/m 2 we found that for tibial tubercle to trochlear groove distance (TT-TG), entry point to trochlear groove angle (EPTG), and entry point to transition point angle (EPTP) cartilage worsening as a single measurement outperformed composite outcomes with higher Z scores. Alternatively, we found that patella tilt angle (PTA) performed best when predicting bone marrow lesion worsening as a single measurement than compared to the composite outcomes. For patellofemoral morphological measures, composite outcomes that combined data on cartilage damage and bone marrow lesion enlargement failed to increase sensitivity to change over outcomes for single structures alone. Other composite outcomes may be more successful in increasing the sensivitiy to change, and this warrants further investigation.