Lower Trochlear Facet Asymmetry Ratio Is Associated with Objective Patellar Instability in a Retrospective MRI Case-Control Study with Patella Alta-Positive Controls

Description

Kuru and co-authors isolate a kneecap groove measurement tied to instability, controlling for kneecap height. Their 2026 retrospective MRI case-control study includes 123 knees. Forty-three had objective patellar instability and 43 were normal-height controls. Another 37 controls share the high kneecap, patella alta, that often accompanies instability, yet are stable. Nine shape parameters were measured, with the alta-positive group as the key comparison.

The trochlear facet asymmetry ratio compares the groove's two slopes. It graded cleanly across the groups. Values ran about 43 percent in unstable knees, 59 percent in alta controls, and 70 percent in normal controls. It discriminated instability best among the measures, and stayed associated after adjustment for kneecap height and age, each extra point of symmetry cutting odds by about ten percent. Two expert readers agreed almost perfectly. The authors propose the ratio as a morphology marker separable from kneecap height.

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Source: https://europepmc.org/article/MED/PMC13467188