Original research Comparison of landing knee valgus angle between female basketball and football athletes: Possible implications for anterior cruciate ligament and patellofemoral joint injury rates Allan Munro * , Lee Herrington, Paul Comfort School of Health Sciences, University of Salford, UK article info Article history: Received 4 August 2011 Received in revised form 21 November 2011 Accepted 30 January 2012 Keywords: Frontal plane projection angle Knee valgus Risk factors Knee injuries ACL PFPS abstract Objective: To evaluate landing strategies of female football and basketball athletes with relation to possible injury mechanisms and disparity in injury. Design: Descriptive laboratory study. Participants: 52 female football players and 41 female basketball players. Main outcome measures: Frontal plane projection angle (FPPA) was measured during the single leg land (SLL) and drop jump (DJ) screening tasks. Results: 2  2  2 mixed factorial ANOVA showed significant main effects were observed for sport, whilst significant interaction effects were seen between sport and task. Females in both sports exhibited significantly greater FPPA values during the SLL task than the DJ task (p < 0.001). Basketball players demonstrated significantly greater FPPA values during SLL than football players (p < 0.001), whilst no differences were found between sports in the DJ task (p ¼ 0.328). Conclusion: Female basketball players display greater FPPA values during unilateral landing tasks than female football players which may reflect the greater ACL injury occurrence in this population. Injury prevention programs in these athletes should incorporate unilateral deceleration and landing tasks and should consider the specific injury mechanisms in each sport. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction A high prevalence of anterior cruciate ligament (ACL) and patellofemoral joint (PFJ) injuries in football (soccer) and basketball players has been widely reported, with females typically at least two times more likely to suffer an ACL or PFJ injury than males (Agel, Olson, Dick, Arendt, Marshall, & Sikka, 2007; Boling, Padua, Marshall, Guskiewicz, Pyne, & Beutler, 2010; Deitch, Starkey, Walters, & Moseley, 2006). Additionally, ACL and PFJ injuries result in a considerable amount of time-loss from sport participa- tion and increased risk of osteoarthritis (Lohmander, Englund, Dahl, & Roos, 2007; Starkey, 2000; Utting, Davies, & Newman, 2005). Most ACL and PFJ injuries occur during non-contact running, jumping and landing tasks (Agel, Arendt, & Bershadsky, 2005; Boden, Dean, Feagin, & Garrett, 2000; Finestone, Milgrom, Evans, Yanovich, Constantin, & Moran, 2008; Hewett, Torg, & Boden, 2009; Krosshaug et al., 2007) with inadequate neuromuscular control of the lower limb during these manoeuvres considered a likely cause of injury (Dierks, Manal, Hamill, & Davis, 2008; Hewett et al., 2005; Myer, Ford, Foss et al., 2010; Souza & Powers, 2009). Decreased knee flexion and increased knee valgus, tibial rotation, hip adduction and internal rotation during landing and cutting manoeuvres are commonly seen during ACL injury episodes (Boden et al., 2000; Hewett et al., 2009; Koga et al., 2010; Krosshaug et al., 2007; Olsen, Myklebust, Engebretsen, & Bahr, 2004) and can increase strain placed on the ACL (Berns, Hull, & Patterson, 1992; Markolf, Burchfield, Shapiro, Shepard, Finerman, & Slauterbeck, 1995). However, only knee valgus angles, moments and differ- ences between limbs during a drop jump task have been cited as a significant predictor of ACL injury (Hewett et al., 2005). The same changes in lower limb posture can increase loads placed upon the PFJ with decreased knee flexion, increased hip internal rotation and increased knee valgus loads having been linked to development of patellofemoral pain syndrome (PFPS) (Boling, Padua, Marshall, Guskiewicz, Pyne, & Beutler, 2009; Lee, Anzel, Bennett, Pang, & Kim, 1994; Myer, Ford, Foss et al., 2010; Stefanyshyn, Stergiou, Lun, Meeuwisse, & Worobets, 2006). The combination of these movements has been called dynamic knee * Corresponding author. University of Salford, Allerton Building, Frederick Road Campus, Salford M6 6PU, UK. Tel.: þ441612956611. E-mail address: A.G.Munro@edu.salford.ac.uk (A. Munro). Contents lists available at SciVerse ScienceDirect Physical Therapy in Sport journal homepage: www.elsevier.com/ptsp 1466-853X/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.ptsp.2012.01.005 Physical Therapy in Sport 13 (2012) 259e264