title: Knee biomechanics during a jump-cut maneuver: effects of sex and ACL surgery.
abstract: OBJECTIVE
  The purpose of this study was to compare kinetic and knee kinematic measurements from male and female anterior cruciate ligament (ACL)-intact (ACLINT) and ACL-reconstructed (ACLREC) subjects during a jump-cut maneuver using biplanar videoradiography.
  
  
  METHODS
  Twenty subjects were recruited; 10 ACLINT (5 men and 5 women) and 10 ACLREC (4 men and 6 women, 5 yr postsurgery). Each subject performed a jump-cut maneuver by landing on a single leg and performing a 45° side-step cut. Ground reaction force (GRF) was measured by a force plate and expressed relative to body weight. Six-degree-of-freedom knee kinematics were determined from a biplanar videoradiography system and an optical motion capture system.
  
  
  RESULTS
  ACLINT female subjects landed with a larger peak vertical GRF (P < 0.001) compared with ACLINT male subjects. ACLINT subjects landed with a larger peak vertical GRF (P ≤ 0.036) compared with ACLREC subjects. Regardless of ACL reconstruction status, female subjects underwent less knee flexion angle excursion (P = 0.002) and had an increased average rate of anterior tibial translation (0.05%·ms ± 0.01%·ms, P = 0.037) after contact compared with male subjects. Furthermore, ACLREC subjects had a lower rate of anterior tibial translation compared with ACLINT subjects (0.05%·ms ± 0.01%·ms, P = 0.035). Finally, no striking differences were observed in other knee motion parameters.
  
  
  CONCLUSIONS
  Women permit a smaller amount of knee flexion angle excursion during a jump-cut maneuver, resulting in a larger peak vertical GRF and increased rate of anterior tibial translation. Notably, ACLREC subjects also perform the jump cut maneuver with lower GRF than ACLINT subjects 5 yr postsurgery. This study proposes a causal sequence whereby increased landing stiffness (larger peak vertical GRF combined with less knee flexion angle excursion) leads to an increased rate of anterior tibial translation while performing a jump-cut maneuver.
authors.affiliation: Department of Orthopaedics, The Warren Alpert Medical School, Brown University and Rhode Island Hospital, Providence, RI 02903, USA.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Miranda
authors.forename: Paul D
authors.initials: PD
authors.lastname: Fadale
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Hulstyn
authors.forename: Robert M
authors.initials: RM
authors.lastname: Shalvoy
authors.forename: Jason T
authors.initials: JT
authors.lastname: Machan
authors.forename: Braden C
authors.initials: BC
authors.lastname: Fleming
mesh_terms: D000328:Adult; D059549:Anterior Cruciate Ligament Reconstruction; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007718:Knee Injuries / Q000503:physiopathology; D007719:Knee Joint / Q000502:physiology* / Q000503:physiopathology; D008297:Male; D009068:Movement / Q000502:physiology*; D012737:Sex Factors; D013977:Tibia / Q000502:physiology / Q000503:physiopathology; D055815:Young Adult