Biomechanical correlation at the knee joint between static lunge and single-leg drop landing - a comparative study among three different toe directions

BACKGROUND: Toe direction is a critical factor affecting knee biomechanics during various movements including closed kinetic chain (CKC) exercise and landing tasks. Physiotherapists always concentrate on the control of toe direction during CKC exercise as a first step for athletes, as it is believed that correction of toe direction during CKC exercise is important to maintain the appropriate toe position even in high demanding activities such as landing tasks. The purpose of the present study was to investigate knee biomechanics during CKC exercise as well as landing tasks with three different toe directions, and clarify whether biomechanical parameters during CKC exercise would be related to those during landing tasks. METHODS: A total of 23 male recreational level athletes (mean age = 20.0 ± 1.1 yrs) participated. Tegner activity score were 7 for all male subjects. First, the subjects performed weight-bearing static lunge tests (SL) under three different toe directions, including 0 degrees (Toe-neutral: TN), 20 degrees (Toe-In: TI), and - 20 degrees (Toe-out: TO). Thereafter, SLDL was done under three different toe directions. Three-dimensional knee kinematics and kinetics at 60 degrees of knee flexion were calculated. As a statistical analysis, Pearson's correlation coefficient was used to evaluate the relationship between SL and SLDL. The statistical significance level wasset at P=0.05. RESULTS AND CONCLUSIONS: Knee abduction angle showed significant correlation between SL and SLDL in all three different directions (TI: r=0.631, p<0.001, TN: r=0.678, p<0.001, TO: r=0.572, p<0.001). In terms of knee internal rotation, strong correlation was also found (TI: r=0.846, p<0.001, TN: r=0.791, p<0.001, TO: r=0.749, p<0.001). In addition, external knee abduction moment presented significant correlation in all three different directions (TI: r=0.574, p<0.001, TN: r=0.499, p<0.01, TO: r=0.469, p<0.01). From the present study, significant correlation between SL and SLDL was found in knee abduction angle, knee internal rotation, and external knee abduction moment under all three different directions including TI, TN, and TO. Physiotherapist should take care of toe direction and reform the movements especially for athletes who present malalignment of the knee joint during SL with TI or TO to prevent ACL injury in landing tasks.