Mechanistic evidence linking TT-TG translation to patellofemoral contact pressure and tibial tubercle position to improve knee joint stability.

BACKGROUND: Patellar instability is a multifactorial condition in which changes in tibial tuberosity-trochlear groove (TT-TG) distance may influence extensor mechanism alignment and patellofemoral loading. However, previous biomechanical studies have often combined TT-TG correction with additional procedures or evaluated only discrete conditions, making it difficult to isolate the independent mechanical effect of TT-TG translation. The present study, therefore, used finite element analysis to examine the isolated effect of TT-TG translation on patellofemoral loading across knee flexion from 0° to 90°. The study aimed to determine whether contact pressure increases as TT-TG deviates from a model-defined reference condition, whether medialization and lateralization produce different mechanical responses, and which flexion ranges are most sensitive to TT-TG variation. HYPOTHESIS: Changes in TT-TG distance will considerably alter patellofemoral loading. METHODS: A finite element (FE) knee model was reconstructed from micro computed tomography data and analyzed in an FE solver. The tibial tubercle was translated only in the mediolateral direction to generate discrete TT-TG states from 0 to 25 mm in 5-mm increments, with reference to a specimen-specific model condition centered at 10 mm. Anterior translation was not included because the purpose of the study was to isolate the mechanical effect of mediolateral TT-TG variation. Knee flexion from 0° to 90° was simulated using a configured FE model. Patellofemoral contact pressure distribution and maximum values were recorded. RESULTS: Maximum contact pressure increased with TT-TG deviation and was asymmetric. Medialization to 0-5 mm increased pressure by 21.9% across 30° to 90°, whereas lateralization to 20-25 mm increased pressure by 9.5% relative to the 10-15 mm model reference range. DISCUSSION: TT-TG translation produced direction- and flexion-dependent changes in patellofemoral loading. Medialization increased contact pressure more than lateralization for comparable deviations, consistent with reports of a higher risk of medial overload after tubercle medialization. These findings provide exploratory biomechanical insights into how isolated TT-TG variation may influence patellofemoral loading under passive-model conditions. LEVEL OF EVIDENCE: V; biomechanical in silico investigation.