279 Journal of Sport Rehabilitation, 2013, 22, 279-287 © 2013 Human Kinetics, Inc. www.JSR-Journal.com ORIGINAL RESEARCH REPORT Gaudreault and Gauthier are with the School of Rehabilitation, University of Sherbrooke, Sherbrooke, Canada. Fuentes and Mezghani are with the Imagery and Orthopedics Research Laboratory, University of Montreal Hospital Center, Montreal, Canada. Turcot is with the Willy Taillard Kinesiology Labora- tory, Geneva University Hospitals, Geneva, Switzerland. Relationship Between Knee Walking Kinematics and Muscle Flexibility in Runners Nathaly Gaudreault, Alex Fuentes, Neila Mezghani, Virginie O. Gauthier, and Katia Turcot Context: Decreased fexibility in muscles and joints of lower extremities is commonly observed in runners. Understanding the effect of decreased fexibility on knee walking kinematics in runners is important because, over time, altered gait patterns can make runners vulnerable to overuse injuries or degenerative pathologies. Objectives: To compare hamstring and iliotibial-band (ITB) fexibility and knee kinematics in runners and nonrunners. Design: A descriptive, comparative laboratory study. Setting: Hamstring and ITB fexibility were measured with the active knee-extension test and the modifed Ober test, respectively, in both groups of participants. Three-dimensional (3D) walking kinematic data were then recorded at the knee using a motion- tracking system. Participants: 18 runners and 16 nonrunners. Main Outcome Measures: Knee-extension angle (hamstring fexibility) and hip-adduction angle (ITB fexibility). Knee kinematic parameters of interest included knee angle at initial contact, peak knee angles, and knee-angle range in all planes of movement. Results: The runners had a signifcantly less fexible ITB than the nonrunners (hip adduction [–] and adduction [+] angles, 3.1° ± 5.6° vs –6.4° ± 4.5°; P < .001). The runners demonstrated a greater mean tibial external-rotation angle at initial contact (7.3° ± 5.8° vs 2.0° ± 4.0°; P = .01) and a smaller mean peak tibial internal-rotation angle (–1.6° ± 3.0° vs –4.2° ± 3.2°; P = .04) than the nonrunners. Conclusion: This study provides new insight into the relationship between muscle fexibility and 3D knee kinematics in runners. This supports the premise that there is an association between muscle fexibility and transverse-plane knee kinematics in this population. Keywords: gait analysis, sports rehabilitation, iliotibial band For many individuals, long-distance running is the sport of choice. This is supported by a search on Run- ning USA and popular North American marathon Web sites (eg, Boston, Ottawa, and New York), which reveals a signifcant increase in the number of participants in these events over the past several years. For example, since 2000, the number of half-marathon fnishers in the United States has more than tripled (from 482,000 to 1,610,000), an increase of 234%. 1 The health benefts and accessibility of this sport certainly contribute to its grow- ing popularity. Nevertheless, running has been frequently associated with musculoskeletal injuries, 2–4 the majority being related to the knee 4,5 and overuse. 4,6 Decreased flexibility of the tensor fascia latae/ iliotibial band (ITB) complex and hamstrings has been commonly reported in runners. 7,8 Anatomical and sci- entifc evidence support the potential role of decreased fexibility of these soft tissues in the pathomechanics of overuse knee injuries. 7,9 The ITB takes its origin in the fascial components of the tensor fascia latae, the gluteus maximus, and the gluteus medius muscles. 10,11 Distally, ITB fbers connect to the linea aspera via the lateral intermuscular septum, terminating just proximal to the lateral condyle of the femur. 10,11 ITB fbers also attach to the patella and to the lateral tibial tubercle, known as Gerdy’s tubercle. Due to its tibial attachment, ITB tight- ness can interfere with internal/external tibial rotation and abduction/adduction movement of the knee during walk- ing. Merican and Amis 12 studied the effect of increasing ITB tension on knee kinematics. They concluded that as the ITB tension increased, the tibia was more externally rotated. However, Merican and Amis’ data were col- lected on cadavers and during an open-kinetic-chain movement, and their results cannot be generalized to an in vivo gait-analysis context. Studying the relationship between decreased ITB fexibility and tibial rotation is clinically relevant because there is evidence that runners with ITB syndrome present changes in tibial rotation compared with symptom-free runners. 13 As regards the hamstrings, they pass across the hip and knee. As the hip goes into fexion during the terminal swing phase of gait, decreased fexibility of the hamstrings can reduce the range of knee-extension movement observed during that period. It can therefore be hypothesized that a greater knee-fexion angle at initial contact could be observed. The contact force between the patella and the femur starts