Journal of Applied Biomechanics, 2013, 29, 141-146 © 2013 Human Kinetics, Inc. An Official Journal of ISB www.JAB-Journal.com ORIGINAL RESEARCH 141 Pedro Rodrigues (Corresponding Author) and Trampas Ten- Broek are with the Biomechanics Laboratory, University of Massachusetts, Amherst, MA, and with New Balance Sports Research Laboratory, Lawrence, MA. Joseph Hamill is with the Biomechanics Laboratory, University of Massachusetts, Amherst, MA. Runners With Anterior Knee Pain Use a Greater Percentage of Their Available Pronation Range of Motion Pedro Rodrigues, 1,2 Trampas TenBroek, 1,2 and Joseph Hamill 1 1 University of Massachusetts; 2 New Balance Sports Research Laboratory “Excessive” pronation is often implicated as a risk factor for anterior knee pain (AKP). The amount deemed excessive is typically calculated using the means and standard deviations reported in the literature. However, when using this method, few studies fnd an association between pronation and AKP. An alternative method of defning excessive pronation is to use the joints’ available range of motion (ROM). The purposes of this study were to (1) evaluate pronation in the context of the joints’ ROM and (2) compare this method to traditional pronation variables in healthy and injured runners. Thirty-six runners (19 healthy, 17 AKP) had their passive pronation ROM measured using a custom-built device and a motion capture system. Dynamic pronation angles during running were captured and compared with the available ROM. In addition, traditional pronation vari- ables were evaluated. No signifcant differences in traditional pronation variables were noted between healthy and injured runners. In contrast, injured runners used signifcantly more of their available ROM, maintaining a 4.21° eversion buffer, whereas healthy runners maintained a 7.25° buffer (P = .03, ES = 0.77). Defning excessive pronation in the context of the joints’ available ROM may be a better method of defning excessive pronation and distinguishing those at risk for injury. Keywords: running, injury, patellofemoral Running is a popular form of exercise, with some 33.2 million Americans using it regularly as a part of their ftness routine. 1 Unfortunately, with all the health benefts that come from a regular running routine also come the increased risk of orthopedic injury. In fact, it has been shown that up to 24% of runners will sustain an injury severe enough to cause them to stop running for seven or more days. 2 Of these injuries, the knee is the most frequently injured region of the body, with anterior knee pain (AKP) being a prevalent diagnosis. 3–6 As with any overuse injury, several factors contribute to the development of AKP, such as training errors, bio- mechanical faults, and anatomical abnormalities. 7 Two biomechanical factors that are frequently implicated in the development of AKP are “excessive” and/or “pro- longed” pronation. 8,9 In this injury paradigm, excessive and/or prolonged pronation are thought to keep the tibia internally rotated as the knee begins to extend, thus disrupting the “screw home mechanism.” 8,9 To preserve this screw home mechanism, the femur is believed to compensate by internally rotating more than the tibia and therefore achieving the required knee external rota- tion needed for the knee to extend. However, while this compensation at the femur is thought to preserve the arthrokinematics at the tibiofemoral joint, it disrupts those of the patellofemoral joint, placing increased stress on its articular cartilage and surrounding soft tissue. 10 While clinically this injury paradigm is widely accepted, research studies have not supported the associa- tion between excessive and/or prolonged pronation and AKP. Prospective and retrospective epidemiology studies have found no association between static and dynamic measures of pronation and the risk of developing AKP in military recruits entering basic training and recreational runners. 2,11–14 Similarly, biomechanical studies do not consistently fnd differences in pronation related variables such as peak eversion, peak tibial internal rotation (TIR), and peak knee internal rotation (KIR) in those with and without AKP. 13,15–17 Collectively, these fndings bring in to question this injury paradigm. While epidemiological and biomechanical studies have not supported the association between AKP and pronation related variables, orthotic studies have painted a different picture. When specifcally focusing on pain and function as outcome measures, these studies consistently fnd orthotics to reduce pain and improve function. 18–20 In fact, Amell et al 18 and Saxena et al 19 both reported that over 70% of participants with AKP reported amelioration in their symptoms following an orthotic intervention. Therefore, orthotic studies provide some