title: Exercise-induced knee joint laxity in distance runners.
abstract: The objectives of this study were to evaluate the effect of exercise on knee joint laxity. If exercise induced laxity is physiological, incorporation of this quality into a ligament replacement material would be indicated. Twenty recreational long distance runners average age 41 (range 24 to 50 yr) were tested before and immediately after 30 minutes of running. Using a computerized goniometer type instrument (Acufex KSS), knee flexion, axial tibial rotation and anterior-posterior tibial displacement were simultaneously recorded, while the runners underwent tests of static as well as dynamic knee joint laxity. At 30 degrees of knee flexion, a maximum increase of 16 per cent in mean total anterior-posterior laxity post-exercise was found. At the examination 30 minutes post-exercise, laxity at 30 degrees of knee flexion was still increased. However, laxity at 90 degrees of knee flexion had decreased to pre-exercise levels or below. Anterior tibial displacement, recorded during eccentric quadriceps activity (0 to 90 degrees of knee flexion) with weights attached to the foot, showed a maximum of 18 per cent increase in total anterior-posterior laxity post-exercise. It is suggested that the laxity increase is caused in part by a true ligamentous laxity increase, and in part by a decreased resting tone of the fatigued muscles.
authors.affiliation: Department of Orthopaedic Surgery, Aarhus County Hospital, University of Aarhus, Denmark.
authors.forename: H V
authors.initials: HV
authors.lastname: Johannsen
authors.forename: T
authors.initials: T
authors.lastname: Lind
authors.forename: B W
authors.initials: BW
authors.lastname: Jakobsen
authors.forename: K
authors.initials: K
authors.lastname: Krøner
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000209:etiology* / Q000503:physiopathology; D007718:Knee Injuries / Q000209:etiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012420:Running / Q000293:injuries*