Tibiofemoral Angle, Not Q-angle, is Related to Frontal Plane Lower Extremity Kinematics During a Weight-Bearing Perturbation

Abstract

2356 Lower extremity alignment (LEA) has been proposed as a risk factor for anterior cruciate ligament injury, however little is known about the relationship between these static measures and dynamic lower extremity (LE) function. PURPOSE: To investigate the relationship between frontal plane measures of static LEA and dynamic LE kinematics during a single-leg weight-bearing perturbation. METHODS: 10 males and 10 females (24.9 ± 4.1 yrs, 171.5 ± 7.7 cm, 73.6 ± 17.2 kg) were measured for standing quadriceps angle (StQ) and standing frontal plane tibiofemoral angle (TFA). StQ was measured as the angle formed by a line from the anterior superior iliac spine (ASIS) to the center of the patella and a line from the center of the patella to the tibial tuberosity. TFA was measured as the angle formed by a line from the midpoint between the ASIS and the greater trochanter to the center of the anterior joint line of the knee, and a line from the center of the anterior joint line of the knee to the midpoint between the medial and lateral malleoli. An electromagnetic tracking system monitored lower extremity kinematics while a lower extremity perturbation device produced a forward and internal rotation perturbation of the trunk and femur on the weight-bearing tibia at 30o of knee flexion. Pearson product correlations compared StQ and TFA with frontal plane kinematics of the hip and knee prior to (initial joint angle) and following (peak joint angle) the perturbation. Hip and knee adduction angles were expressed as positive values and abduction angles as negative values. RESULTS: Means ± sd for StQ and TFA were 14.6 ± 5.5o and 10.6 ± 1.7o respectively. Intratester reliability estimates for StQ (ICC = .96, SEM = 1.2 o) and TFA (ICC = .88, SEM = 0.7 o) confirmed high measurement consistency. Means ± sd for initial and peak joint angles were 9.2 ± 6.6° and 7.8 ± 5.9° of hip adduction and 1.0 ± 4.9° and 3.3 ± 5.6° of knee adduction. While no relationship was observed between StQ and hip and knee adduction angles, TFA was positively correlated with initial (r = .482, P = .03) and peak (r = .542, P = .01) hip adduction, and negatively correlated with initial (r = −.607, P = .01) and peak (r = −.439, P = .05) knee adduction. StQ and TFA were not related (r = .002, P = .99). CONCLUSION: These results suggest that TFA may be a better predictor of dynamic lower extremity frontal plane motion than StQ during a single-leg weight-bearing perturbation. The positive correlation with hip adduction and negative correlation with knee adduction implies that increased TFA may contribute to greater valgus angulation at the knee during similar weight-bearing tasks.