title: Role of peripatellar retinaculum in transmission of forces within the extensor mechanism.
abstract: BACKGROUND
  The role of the peripatellar retinaculum as a frontal plane stabilizer of the patellofemoral joint has been well established. However, as a result of its unique orientation, the retinaculum also may influence the distribution of forces within the extensor mechanism. The objective of this study was to determine the extent to which the peripatellar retinaculum affects the magnitude of forces experienced by the patellar tendon.
  
  
  METHODS
  Ten cadaver knees were used in this investigation. Each was mounted on a custom test apparatus that was fixed to an Instron frame. The extensor mechanism was loaded by applying forces through the individual heads of the quadriceps femoris. Patellar tendon tension was measured at 0 degrees , 20 degrees , 40 degrees , and 60 degrees of knee flexion with use of a buckle transducer under two conditions: (1) with the peripatellar retinaculum intact, and (2) with the peripatellar retinaculum removed. Patellar tendon tension was compared between the two conditions across the knee flexion angles.
  
  
  RESULTS
  At each knee flexion angle, the patellar tendon tension was greater with the retinaculum removed than it was with the retinaculum intact. However, the difference was significant only at 0 degrees and 60 degrees , at which positions the force transmitted to the patellar tendon was increased by 16.6% and 9.6%, respectively.
  
  
  CONCLUSIONS
  The observed increases in patellar tendon tension after removal of the peripatellar retinaculum is an indication of the load-sharing function of that structure as a part of the extensor mechanism.
  
  
  CONCLUSIONS
  Our results suggest that compromise of the peripatellar retinaculum may alter patellar tendon and/or patellofemoral joint forces.
authors.affiliation: Orthopaedic Biomechanics Laboratory, VA Long Beach Healthcare System, Long Beach, California, USA. powers@usc.edu
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Powers
authors.forename: Yu-Jen
authors.initials: YJ
authors.lastname: Chen
authors.forename: Shawn
authors.initials: S
authors.lastname: Farrokhi
authors.forename: Thay Q
authors.initials: TQ
authors.lastname: Lee
mesh_terms: D001696:Biomechanical Phenomena; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D013710:Tendons / Q000502:physiology*