title: ACL Deficiency Increases Forces on the Medial Femoral Condyle and the Lateral Meniscus with Applied Rotatory Loads.
abstract: BACKGROUND
  The articular surfaces and menisci act with the anterior cruciate ligament (ACL) to stabilize the knee joint. Their role in resisting applied rotatory loads characteristic of instability events is unclear despite commonly observed damage to these intra-articular structures in the acute and chronic ACL injury settings.
  
  
  METHODS
  Ten fresh-frozen human cadaveric knees were mounted to a robotic manipulator. Combined valgus and internal rotation torques were applied in the presence and absence of a 300-N compressive load. Forces carried by the individual menisci and via cartilage-to-cartilage contact on each femoral condyle in ACL-intact and ACL-sectioned states were measured using the principle of superposition.
  
  
  RESULTS
  In response to applied valgus and internal rotation torques in the absence of compression, sectioning of the ACL increased the net force carried by the lateral meniscus by at most 65.8 N (p < 0.001). Moreover, the anterior shear force carried by the lateral meniscus increased by 25.7 N (p < 0.001) and 36.5 N (p = 0.042) in the absence and presence of compression, respectively. In response to applied valgus and internal rotation torques, sectioning of the ACL increased the net force carried by cartilage-to-cartilage contact on the medial femoral condyle by at most 38.9 N (p = 0.006) and 46.7 N (p = 0.040) in the absence and presence of compression, respectively. Additionally, the lateral shear force carried by cartilage-to-cartilage contact on the medial femoral condyle increased by at most 21.0 N (p = 0.005) and by 28.0 N (p = 0.025) in the absence and presence of compression, respectively. Forces carried by the medial meniscus and by cartilage-to-cartilage contact on the lateral femoral condyle changed by <5 N as a result of ACL sectioning.
  
  
  CONCLUSIONS
  ACL sectioning increased the net forces carried by the lateral meniscus and medial femoral condyle-and the anterior shear and lateral shear forces, respectively-in response to multiplanar valgus and internal rotation torque.
  
  
  CONCLUSIONS
  These loading patterns provide a biomechanical rationale for clinical patterns of intra-articular derangement such as lateral meniscal injury and osseous remodeling of the medial compartment seen with ACL insufficiency.
authors.affiliation: Sports Medicine and Shoulder Service (L.S.M., T.L.W., and A.D.P.) and Biomechanics Department (J.B.-P., R.K., K.S., and C.W.I.), Hospital for Special Surgery, New York, NY lucas.s.mcdonald@gmail.com.
authors.forename: Lucas S
authors.initials: LS
authors.lastname: McDonald
authors.affiliation: Sports Medicine and Shoulder Service (L.S.M., T.L.W., and A.D.P.) and Biomechanics Department (J.B.-P., R.K., K.S., and C.W.I.), Hospital for Special Surgery, New York, NY boormanpadgettj@hss.edu.
authors.forename: James
authors.initials: J
authors.lastname: Boorman-Padgett
authors.affiliation: Sports Medicine and Shoulder Service (L.S.M., T.L.W., and A.D.P.) and Biomechanics Department (J.B.-P., R.K., K.S., and C.W.I.), Hospital for Special Surgery, New York, NY bobbykent14@gmail.com.
authors.forename: Robert
authors.initials: R
authors.lastname: Kent
authors.affiliation: Sports Medicine and Shoulder Service (L.S.M., T.L.W., and A.D.P.) and Biomechanics Department (J.B.-P., R.K., K.S., and C.W.I.), Hospital for Special Surgery, New York, NY stoneyfigo2525@gmail.com.
authors.forename: Kyle
authors.initials: K
authors.lastname: Stone
authors.affiliation: Sports Medicine and Shoulder Service (L.S.M., T.L.W., and A.D.P.) and Biomechanics Department (J.B.-P., R.K., K.S., and C.W.I.), Hospital for Special Surgery, New York, NY wickiewiczt@hss.edu.
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Wickiewicz
authors.affiliation: Sports Medicine and Shoulder Service (L.S.M., T.L.W., and A.D.P.) and Biomechanics Department (J.B.-P., R.K., K.S., and C.W.I.), Hospital for Special Surgery, New York, NY pearlea@hss.edu.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Pearle
authors.affiliation: Sports Medicine and Shoulder Service (L.S.M., T.L.W., and A.D.P.) and Biomechanics Department (J.B.-P., R.K., K.S., and C.W.I.), Hospital for Special Surgery, New York, NY imhauserc@hss.edu.
authors.forename: Carl W
authors.initials: CW
authors.lastname: Imhauser
mesh_terms: D016118:Anterior Cruciate Ligament / Q000502:physiology*; D001696:Biomechanical Phenomena / Q000502:physiology; D005269:Femur / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008592:Menisci, Tibial / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D019415:Torque