This prospective single-center observational cohort study will evaluate the relationship between anterior knee pain and patellar tendon elasticity after infrapatellar tendon-split tibial intramedullary nailing. Adult patients undergoing standard tibial intramedullary nailing through an infrapatellar tendon-split approach will be enrolled after ethics approval. Patellar tendon elasticity will be assessed using shear-wave ultrasound elastography before surgery and during follow-up at 6 weeks, 3 months, and 6 months. Clinical outcomes will include anterior knee pain severity, patellofemoral function, tendon-related symptoms, and knee range of motion. Inter-rater reliability between two independent radiologists will also be evaluated.