In Vivo Arthroscopic Behavior of the Infrapatellar Plica of the Knee
Condition: Anterior Knee Pain Syndrome
MeSH terms: Patellofemoral Pain Syndrome
Study type: Observational

Summary: 
      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.
    

Detailed description: 
      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.
    

Intervention name(s): observation of the behavior of the infrapatellar plica
Intervention type(s): Procedure
Intervention description(s): Local anesthesia using bupivicaine will be initiated. The IPP, if present will be injected with contrast material. In order to minimize discomfort, lidocaine 1%, in as small a volume as possible, will be injected into the fat pad under direct vision to avoid any intra-articular damage from the #25 needle. Radiographic visualization will be verified and the knee taken through a full range of passive and active exercises. Active quadriceps contraction in the subject will be performed at 0, 15, 30 60 and 90 degrees of flexion. In so far as is technically possible, the behavior of the IPP will be videotaped and recorded on lateral fluoroscopy.
Other intervention name(s): Knee surgery
Observational model: Case-Only
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Inclusion:

        Healthy subject >18 years of age, skeletally mature Pending knee joint arthroscopy.

        Exclusion:

        Active infection
      
Keywords: Knee physiology; Anterior compartment knee; Infrapatellar plica; Ligamentum mucosum; Enthesis organ; Fat pad of the knee; Patellofemoral kinematics