SAGITTAL PLANE TRANSLATIONS OF THE KNEE IN ANTERIOR CRUCIATE-DEFICIENT SUBJECTS AND CONTROLS

Static anterior-posterior (AP) laxity is one of the commonly used crit eria in selecting patients for cruciate ligament reconstructions, but in reality dynamic AP laxity plays a more important role. The aim of t his in vivo study was to compare the sagittal translation of the knee during active and passive motion, signifying dynamic AP laxity, viith static AP laxity in healthy subjects (controls) and patients with ante rior cruciate ligament deficiency. The sagittal plane knee translation s were recorded and compared in both knees of nine healthy subjects (C ontrols) and seven patients with confirmed unilateral ACL deficiency d uring dynamic and static situations with an electrogoniometer system. In all groups during the ascents the tibia moved anteriorly in relatio n to the femur, whereas during the descents it moved posteriorly. The static anterior-posterior translation was significantly smaller in the control knee than in both healthy and injured knees of the ACL defici ent group (P < 0.05). The injured knee showed the same laxity (92%) as the uninjured knee during dynamic activities, but it was 46% of stati c laxity. Also in the injured knees, the dynamic active laxity was lar ger during descents than ascents (P < 0.05). The results indicate that there is also a change in mechanics of the noninjured knee following injury to the contralateral knee and that this population of patients with ACL deficiency had good control over their abnormal anterior-post erior laxity.