Anterior Knee Pain and Patellar Tendon Elasticity After Infrapatellar Tendon-Split Tibial Intramedullary Nailing

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.

Inclusion Criteria: * Age 18 to 65 years * Unilateral tibial shaft or metaphyseal fracture * Planned treatment with infrapatellar tendon-split tibial intramedullary nailing * Ability to complete baseline and follow-up assessments * Written informed consent Exclusion Criteria: * Previous surgery on the same knee * Previous patellar tendon rupture or known patellar tendon disorder * Active inflammatory rheumatologic disease * Chronic systemic corticosteroid therapy or long-term immunosuppressive treatment * Significant peripheral neuropathy or advanced diabetic neuropathy * Bilateral tibial fracture * Additional major lower-extremity injury or surgery affecting assessment * Inability to comply with scheduled follow-up visits