Relationship of anterior knee laxity to knee translations during drop landings: a bi-plane fluoroscopy study.

Abstract

Passive anterior knee laxity has been linked to non-contact ACL injury risk. High deceleration movements have been implicated in the non-contact ACL injury mechanism, and evidence suggests that greater anterior tibial translations (ATT) may occur in healthy knees that are lax compared to a tight knee. The purpose of this study was to determine the relationship between anterior knee laxity scores and ATT during drop landings using biplane fluoroscopy. Sixteen healthy adults (10 women; 6 men) performed stiff drop landings (40 cm) while being filmed using a high-speed, biplane fluoroscopy system. Initial, peak and excursions for rotations and translations were calculated and regression analysis used to determine the 6DoF kinematic relationships with KT1000 scores with peak ATT occurring during the landing. KT1000 values were (+) correlated with peak ATT values for group (r = 0.89; P < 0.0001) and both genders (males, r = 0.97; P = 0.0003; females, r = 0.93; P = < 0.0001). Regression analysis yielded a significant linear fit for the group (r (2) = 0.80; Y (ATT-group) = - 0.516 + 1.2 × X (KT1000-group)) and for each gender (females: r(2) = 0.86; Y (ATT-females) = 0.074 + 1.2 × X (KT1000-females) and males: r (2) = 0.94; Y (ATT-males) = - 0.79 + 1.2 × X (KT1000-males)). A strong relationship was observed between passive anterior knee laxity measured via KT1000 and peak ATT experienced during dynamic activity in otherwise healthy persons performing a stiff drop-landing motion.