The role of sagittal tibial tubercle–trochlear groove distance in patellofemoral joint loading: a computational modeling analysis

AbstractBackground The tibial tubercle–trochlear groove (TT-TG) distance is a key metric in evaluating patellofemoral (PF) pathology, with increased values linked to instability and cartilage degeneration. The sagittal TT-TG (sTT-TG), defined as the horizontal distance between the trochlear groove and tibial tubercle in the sagittal plane, may offer insights into PF joint loading. However, its relationship to contact pressure and the influence of femoral rollback, patella height, and joint line height remain unclear. Purpose To investigate the relationship between sTT-TG and PF contact pressure and assess how femoral rollback, patellar height, and joint line height influence sTT-TG and PF loading. Methods A two-dimensional sagittal knee model was developed. Outputs included sTT-TG, patellar tendon angle (PTA), and PF contact pressure. Simulations were performed from 0° to 140° flexion. Tibial tubercle position was varied (±10 mm), joint line height shifted (±10 mm), and patellar tendon length altered (±30%) to simulate patella alta and baja. Sensitivity analysis quantified effects. Results Posteriorizing the tubercle by 10 mm increased PF pressure by 29.4% at 0° and 27.5% at 30°; anteriorization reduced it by 21.6% and 18.2%, respectively. Femoral rollback led to a 5.5 mm decrease in sTT-TG up to 60°. Patella baja increased, and alta decreased, PF pressure by ∼9%, with minimal sTT-TG changes. Joint line shifts affected pressure but not sTT-TG. Conclusion sTT-TG is a biomechanically relevant, flexion-dependent parameter for assessing PF joint loading, but its interpretation must consider patella and joint line height.