Anterior knee pain post-multiple surgeries for tibia fracture effectively managed with infrapatellar fat pad injection: a case report

BACKGROUND: The anterior knee compartment is filled by the infrapatellar fat pad (IFP) and has been emphasized as a source of anterior knee pain (AKP). CASE PRESENTATION: A 51-year-old woman sustained a right tibial plateau and open diaphyseal fracture 2 years earlier. She remained with chronic AKP after undergoing bone fixations. Increased anterior portion of the IFP brightness and decreased adipose tissue gliding with flexion and extension compared to the unaffected side was shown on ultrasonography. An injection of 0.2% lidocaine between the patellar tendon and IFP, and into the IFP under ultrasound guidance, immediately relieved the pain. The pain kept recurring although injections were effective for a while; thus, surgery was scheduled. Scar tissue on the IFP surface was endoscopically excised and her pain dramatically reduced. CONCLUSION: This is the first report in which the detection of increased brightness on ultrasound of IFP and the injections into the IFP triggered an additional surgical intervention. Ultrasound evaluation and injection may be beneficial in pain clinic patients presenting with AKP and may provide an opportunity for diagnosis.