QUANTITATIVE-ANALYSIS OF ANTERIOR CRUCIATE LIGAMENT INSTABILITY

The purpose of this study was to quantify end-feel by evaluating insta ntaneous stiffness and change in stiffness of the tibiofemoral joint. Normal (n = 26), anterior cruciate ligament (ACL) deficient (n = 6), a nd posterior cruciate ligament (PCL) deficient (n = 2) subjects were t ested using the KT 2000 knee ligament arthrometer. Analogue force and displacement data were digitized, filtered, and calibrated. Force-disp lacement curves in the region of anterior tibial displacement were app roximated using 5th degree polynomial functions. Stiffness and change in stiffness were determined analytically by the first and second deri vatives of these functions. Subjects with confirmed ACL deficiency had lower values for stiffness and change in stiffness in the region of t he curves believed to be indicative of ACL function, compared to contr alateral knees and control subjects. Relevance First and second deriva tives of tibiofemoral force-displacement curves give the stiffness and the change in stiffness respectively for anterior displacement of the tibia relative to the femur, This information concerning knee stabili ty in vivo may be useful for diagnosis and follow-up.