Exercise-induced knee joint laxity in distance runners

• Published in: British journal of sports medicine Vol. 23; no. 3; pp. 165 - 168
• Main Authors: Johannsen, H V, Lind, T, Jakobsen, B W, Krøner, K
• Format: Journal Article
• Language: English
• Published: England BMJ Publishing Group Ltd and British Association of Sport and Exercise Medicine 01-09-1989; BMJ Publishing Group LTD
• Subjects: Adult; Biomechanical Phenomena; Female; Humans; Joint Instability - etiology; Joint Instability - physiopathology; Knee Injuries - etiology; Knee Injuries - physiopathology; Male; Middle Aged; Running - injuries
• ISSN: 0306-3674; 1473-0480
• DOI: 10.1136/bjsm.23.3.165

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.