Foot and Hip Contributions to High Frontal Plane Knee Projection Angle in Athletes: A Classification and Regression Tree Approach

Abstract

Study Design Cross-sectional. Objective To investigate predictors of increased frontal plane knee projection angle (FPKPA) in athletes. Background The underlying mechanisms that lead to increased FPKPA are likely multifactorial and depend on how the musculoskeletal system adapts to the possible interactions between its distal and proximal segments. Bivariate and linear analyses traditionally employed to analyze the occurrence of increased FPKPA are not sufficiently robust to capture complex relationships among predictors. The investigation of nonlinear interactions among biomechanical factors is necessary to further our understanding of the interdependence of lower-limb segments and resultant dynamic knee alignment. Methods The FPKPA was assessed in 101 athletes during a single-leg squat and in 72 athletes at the moment of landing from a jump. The investigated predictors were sex, hip abductor isometric torque, passive range of motion (ROM) of hip internal rotation (IR), and shank-forefoot alignment. Classification and regression trees were used to investigate nonlinear interactions among predictors and their influence on the occurrence of increased FPKPA. Results During single-leg squatting, the occurrence of high FPKPA was predicted by the interaction between hip abductor isometric torque and passive hip IR ROM. At the moment of landing, the shank-forefoot alignment, abductor isometric torque, and passive hip IR ROM were predictors of high FPKPA. In addition, the classification and regression trees established cutoff points that could be used in clinical practice to identify athletes who are at potential risk for excessive FPKPA. Conclusion The models captured nonlinear interactions between hip abductor isometric torque, passive hip IR ROM, and shank-forefoot alignment. J Orthop Sports Phys Ther 2012;42(12):996–1004, Epub 18 September 2012. doi:10.2519/jospt.2012.4041

Complex systems approach for sports injuries: moving from risk factor identification to injury pattern recognition—narrative review and new concept

“…In medicine, the array of recursive partitioning based methods such as classification and regression trees (CART), random forests and boosting, which allow non-linear interactions among predictors, as well as depict and make use of these interactions, have been successful in identifying the subset of risk and predictive factors to explain different outcomes 30 39 40. Bittencourt et al 30 have used CART to predict high frontal plane knee angle (DKV) during landing from a vertical jump 30.…”

“…For example: DKV (high frontal plane knee angle) has been associated with hip abductor weakness 29 30. In a linear view, one could assume that the weaker the hip abductors, the larger the DKV.…”

“…In a linear view, one could assume that the weaker the hip abductors, the larger the DKV. However, evidence has shown a non-linear relationship between hip muscle strength and DKV 30. When participants have high hip internal rotation stiffness (as in the case of hip retroversion), even a high strength level of the hip abductor is not capable of preventing DKV 30.…”

“…However, evidence has shown a non-linear relationship between hip muscle strength and DKV 30. When participants have high hip internal rotation stiffness (as in the case of hip retroversion), even a high strength level of the hip abductor is not capable of preventing DKV 30. There are several examples in the sports literature in which a variable is important but not determinant for injury occurrence 31–33.…”

Clinical assessment of countermovement jump landing kinematics in early adolescence: Sex differences and normative values

“…Cameras were positioned at a height of 1.03 m in the frontal and sagittal planes. Twodimensional analysis has previously been shown to be a valid method of quantifying and measuring lower limb kinematics (Bittencourt et al, 2012;McLean et al, 2005;Norris and Olson, 2011).…”