Identifying Relationships Among Lower Extremity Alignment Characteristics (Original Research) (Report‪)‬

Lower extremity alignment has been proposed as a risk factor for acute and chronic lower extremity injuries, including patellofemoral syndrome, (1-3) anterior cruciate ligament injuries, (4-7) medial tibial stress syndrome, (8) stress fractures, and plantar fasciitis. (8) It has been suggested that biomechanical changes resulting from abnormal alignment may influence joint loads, mechanical efficiency of muscles, and proprioceptive orientation and feedback from the hip and knee, resulting in altered neuromuscular function and control of the lower extremities. (4,9,10) However, the relationship between anatomical alignment and injury risk remains poorly understood. Most investigators have examined only one alignment factor or a small number of alignment factors. Given the potential interdependence of various alignment faults along the lower kinetic chain, (4-7,11) examining only one or a limited number of alignment factors may not adequately describe the position of the lower extremity, providing insufficient information to identify clinically meaningful relationships. Accounting for the alignment of the entire lower extremity, rather than a single segment, may more accurately describe the relationship between anatomic alignment and the risk of lower extremity injury, because one alignment characteristic may interact with or cause compensations at other bony segments. (4,12) The potential for an interactive effect among alignment characteristics is illustrated by a study (10) evaluating the independent and combined effects of excessive quadriceps angle and navicular drop on neuromuscular timing and amplitude of the lower extremity muscles in response to postural perturbations. Participants classified as having above-average navicular drop and quadriceps angles exhibited very different neuromuscular responses (ie, amplitude and reflex time of the thigh musculature), depending on whether one or both of these alignment characteristics was present. The potential for the interaction of alignment variables to affect dynamic knee function (10) and predict the likelihood of suffering lower extremity injuries (4-6) reinforces the need to take a more comprehensive approach if we are to fully understand the relationships among lower extremity alignment, dynamic lower extremity function, and risk of injury.