title: Associated lateral/medial knee instability and its relevant factors in anterior cruciate ligament-injured knees.
abstract: BACKGROUND
  Associations of lateral/medial knee instability with anterior cruciate ligament (ACL) injury have not been thoroughly investigated. The purposes of this study were to investigate whether lateral/medial knee instability is associated with ACL injury, and to clarify relevant factors for lateral/medial knee instability in ACL-injured knees.
  
  
  METHODS
  One hundred and nineteen patients with unilateral ACL-injured knees were included. Lateral/medial knee instability was assessed with varus/valgus stress X-ray examination for both injured and uninjured knees by measuring varus/valgus angle, lateral/medial joint opening, and lateral/medial joint opening index. Manual knee instability tests for ACL were evaluated to investigate associations between lateral/medial knee instability and anterior and/or rotational instabilities. Patients' backgrounds were evaluated to identify relevant factors for lateral/medial knee instability. Damage on the lateral collateral ligament (LCL) on MRI was also evaluated.
  
  
  RESULTS
  All parameters regarding lateral knee instability in injured knees were significantly greater than in uninjured knees. There were significant correlations between lateral knee instability and the Lachman test as well as the pivot shift test. Patients with LCL damage had significantly greater lateral joint opening than those without LCL damage on MRI. Sensitivity of LCL damage on MRI to lateral joint opening was 100%, while its specificity was 36%. No other relevant factors were identified. In medial knee instability, there were also correlations between medial knee instability and the Lachman test/pivot shift test. However, the correlations were weak and other parameters were not significant.
  
  
  CONCLUSIONS
  Lateral knee instability was greater in ACL-deficient knees than in uninjured knees. Lateral knee instability was associated with ACL-related instabilities as well as LCL damage on MRI, whereas MRI had low specificity to lateral knee instability. On the other hand, the association of medial knee instability on ACL-related instability was less than that of lateral knee instability.
  
  
  METHODS
  Level IV, case series with no comparison group.
authors.affiliation: Department of Joint Surgery and Sports Medicine, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyoku, Tokyo 113-8519, Japan.
authors.forename: Arata
authors.initials: A
authors.lastname: Yuuki
authors.affiliation: Department of Joint Surgery and Sports Medicine, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyoku, Tokyo 113-8519, Japan; Department of Orthopaedic Surgery, Tokyo Medical and Dental University Hospital of Medicine, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Muneta
authors.affiliation: Department of Joint Surgery and Sports Medicine, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyoku, Tokyo 113-8519, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Ohara
authors.affiliation: Department of Orthopaedic Surgery, Tokyo Medical and Dental University Hospital of Medicine, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Sekiya
authors.affiliation: Department of Joint Surgery and Sports Medicine, Graduate School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima Bunkyoku, Tokyo 113-8519, Japan; Department of Orthopaedic Surgery, Tokyo Medical and Dental University Hospital of Medicine, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan. Electronic address: koga.orj@tmd.ac.jp.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Koga
mesh_terms: D000293:Adolescent; D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015601:Injury Severity Score; D007593:Joint Instability / Q000000981:diagnostic imaging* / Q000209:etiology* / Q000503:physiopathology; D007718:Knee Injuries / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology; D012016:Reference Values; D012189:Retrospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D013997:Time Factors; D055815:Young Adult