Ultrasound Characteristics of the Infrapatellar Fat Pad Under Physiological and Pathological Conditions

The infrapatellar fat pad (IFP) is an intracapsular, extra-synovial adipose tissue located beneath the patellar tendon. It serves as a protective cushion for the knee, mitigating the mechanical impact of various movements. Furthermore, the IFP possesses a robust vascular network and strong secretory capacity, enabling it to contribute to the resolution of various inflammatory processes associated with knee pathology. Magnetic resonance imaging (MRI) is widely used to assess the IFP, but it is limited by high cost, long examination times, and an inability to provide real-time dynamic evaluation. Ultrasound offers a cost-effective, portable, and clinically accessible alternative for IFP imaging. Beyond visualizing the dynamic morphology of the IFP, advances in Doppler ultrasound and elastography now enable the assessment of blood supply and mechanical properties. This review summarizes the ultrasound features of the IFP under physiological and pathological conditions, explores its potential applications in the diagnosis and evaluation of IFP-related disorders, and highlights future directions, with particular emphasis on the role of dynamic ultrasound in evaluating anterior knee disorders in sports medicine.