title: Change with increasing age in control of the lower limbs during jump-landing in adolescents: a 5-year prospective study.
abstract: BACKGROUND
  A discrepancy in the incidence of anterior cruciate ligament injury in males and females appears after puberty; however, little is known about changes that occur in control of the lower limbs during jump-landing in adolescents.
  
  
  METHODS
  Twenty-five male and 29 female 5th grade students (age 10-11 years) participated at the beginning of study and were followed for 5 consecutive years. Control of the lower limbs during jump-landing was evaluated by use of a drop-jump test and 2-dimensional video analysis. The K/H ratio, which was determined by dividing the knee-separation distance by the hip-separation distance, was calculated for initial contact (IC) and for maximum knee flexion (MKF).
  
  
  RESULTS
  In all grades female subjects had a significantly lower K/H ratio at both IC and MKF than male subjects. Although no statistically significant difference in K/H ratio between age categories was shown at either IC or MKF for male subjects, K/H ratio at IC and MKF decreased significantly between 5th grade and 9th grade for female subjects.
  
  
  CONCLUSIONS
  This study suggests that adolescent females have a lower K/H ratio during jump-landing than male subjects of the same age, and that K/H ratio for females decreases with increasing age.
authors.affiliation: Department of Orthopaedic Surgery, Hirosaki University Graduate School of Medicine, Zaifu-cho 5, Hirosaki, Aomori, 036-8562, Japan, shizuka@cc.hirosaki-u.ac.jp.
authors.forename: Shizuka
authors.initials: S
authors.lastname: Sasaki
authors.forename: Eiichi
authors.initials: E
authors.lastname: Tsuda
authors.forename: Yuji
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Shugo
authors.initials: S
authors.lastname: Maeda
authors.forename: Yoshimitsu
authors.initials: Y
authors.lastname: Hayashi
authors.forename: Yuka
authors.initials: Y
authors.lastname: Kimura
authors.forename: Eiji
authors.initials: E
authors.lastname: Sasaki
authors.forename: Yuki
authors.initials: Y
authors.lastname: Fujita
authors.forename: Ippei
authors.initials: I
authors.lastname: Takahashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Umeda
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Nakaji
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Ishibashi
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D011187:Posture / Q000502:physiology; D011446:Prospective Studies; D013177:Sports / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult