title: Tibial displacement and rotation during seated knee extension and wall squatting: a comparative study of tibiofemoral kinematics between chronic unilateral anterior cruciate ligament deficient and healthy knees.
abstract: BACKGROUND
  Following anterior cruciate ligament (ACL) rupture, the knee becomes unstable with alterations in joint kinematics including anterior tibial displacement (ATD), and internal tibial rotation. Therapeutic exercises that promote faulty kinematics should be discouraged, especially early post-reconstruction, to avoid graft stretching and possibly longer-term osteoarthritis. Our study aimed to compare ATD and tibial rotation during two commonly prescribed exercises, namely: open kinetic chain (OKC) seated extension and closed kinetic chain (CKC) single leg wall squatting in ACL-deficient and healthy knees.
  
  
  METHODS
  Eight ACL-deficient patients and eight healthy subjects matched for age, gender and sports history were assessed using Qualisys 3D-Motion Analysis System to track 17 infrared markers while performing a seated knee extension with 3kg weight and a unilateral wall squat. We developed a model to measure joint kinematics through 70° of knee flexion and extension. ANOVA and paired t-tests compared relative ATD and tibial rotation between exercises and groups at 10° increments of flexion and extension.
  
  
  RESULTS
  We found increased ATD in the wall squat compared to the seated extension (p=0.049). There was no difference in ATD between the healthy and ACL-deficient knees but overall the tibia was significantly more internally rotated (p=0.003) in ACL-deficient knees, irrespective of the exercise, possibly interfering with the screw-home mechanism.
  
  
  CONCLUSIONS
  CKC exercises, in particular wall squats, are not necessarily safer for patients with ACL-deficiency and possibly ACL-reconstruction; although generalization should only be made with appropriate caution. Clinicians require a detailed knowledge of the effect of exercise on knee joint kinematics.
authors.affiliation: Faculty of Science, Health, Education and Engineering, The University of the Sunshine Coast, Queensland, Australia. slkeays@optusnet.com.au
authors.forename: S L
authors.initials: SL
authors.lastname: Keays
authors.forename: M
authors.initials: M
authors.lastname: Sayers
authors.forename: D B
authors.initials: DB
authors.lastname: Mellifont
authors.forename: C
authors.initials: C
authors.lastname: Richardson
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D002908:Chronic Disease; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015601:Injury Severity Score; D031221:Knee Dislocation / Q000209:etiology / Q000503:physiopathology / Q000534:rehabilitation*; D007718:Knee Injuries / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000534:rehabilitation*; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D011187:Posture; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology*; D012016:Reference Values; D018570:Risk Assessment; D016896:Treatment Outcome; D055815:Young Adult