In Vivo Arthroscopic Behavior of the Infrapatellar Plica of the Knee

Overview

Anterior knee pain has been an enigmatic problem for orthopedic surgeons. Recent studies, as well as the clinical observation of the principle investigator have suggested that arthroscopic resection of the infrapatellar plica (IPP), a vestigial remnant from embryonic development of no known clinical or biological significance, may eliminate this pain. The mechanism whereby this pain is related to the IPP is unclear. This study will document the mechanical behavior of the IPP, its kinematics, as recorded on video among a group of subjects who are undergoing arthroscopy. Radiographic visualization of the observed behavior will be obtained by injection of contrast material, and then fluoroscopic recording of a standard series of motions. The plica will then be resected to avoid any possibility of residual symptoms related to its presence. Further fluoroscopy of the knee without plical attachment, will allow the kinematic behavior to be assessed. The procedure will then be terminated.

The infrapatellar plica (IPP) of the human knee is vestigial remnant of the embryologic division between the medial and lateral compartments of the knee, present in 85.5% of knees1, felt by some to be of no clinical significance other than acting as a block to visualization an movement during arthroscopy.2 S.J. Kim 3,4, C.R. Boyd 5, and B. Demirag 2006 have documented successful relier of anterior knee pain after resection of the IPP. This study seeks to assess the relationship between knee motion, activation of the extensor apparatus, and the IPP, in essence, the kinematics of the contents of the anterior compartment of the knee. The hypothesis to be evaluated is: the infrapatellar plica is a structure of fundamental biomechanical significance, allowing the transmission of force from the extensor apparatus to the distal femur through the fat pad, and acting as a restraint and a modulator of fad pad mobility. Subjects will be identified by the PI at their office visit. The subject will be consented. The consent will be discussed and verified in a second office visit before surgery. The subject will undergo arthroscopy specifically directed toward identifying and treating known pathology. Once this is finished, if an IPP is present, it will be injected with radiographic contrast material. A series of maneuvers will be performed involving passive and active motion of the knee and active contraction of the quadriceps apparatus. Videotape recording and fluoroscopy will be undertaken. The plica will be removed. Another fluoroscopy will be performed. The patient will be followed according to the standard practice for arthroscopy and the defined pathology.