Influence of an infrapatellar fat pad edema on patellofemoral biomechanics and knee kinematics: a possible relation to the anterior knee pain syndrome

Introduction An edema of the infrapatellar fat pad following knee arthroscopy or in case of chronic anterior knee pain syndrome is suspected to increase the patellofemoral pressure by a modification of the patellofemoral glide mechanism. The study was performed to evaluate this hypothesis. Materials and methods Isokinetic knee extension from 120° of flexion to full extension was simulated on 10 human knee cadaver specimens (six males, four females, average age at death 42 years) using a knee kinemator. Joint kinematics was evaluated by ultrasound sensors (CMS 100 TM , Zebris, Isny, Germany), and retro-patellar contact pressure was measured using a thin-film resistive ink pressure system (K-Scan TM 4000, Tekscan, Boston). Infrapatellar tissue pressure was analyzed using a closed sensor cell which was implanted inside the fat pad (GISMA, Buggingen, Germany). An inflatable fluid cell was implanted by ultrasound control in the center of the infrapatellar fat pad and filled subsequently with water to simulate a fat pad edema. All parameters were recorded and analyzed from 0 to 5 ml volume of the fluid cell. Results Simulating a fat pad edema resulted in a significant ( P