Introduction Anterior knee pain (AKP) is known as a very common problem in the sporting popula- tion. 1,5,15,16,30 Many of the patients with anterior knee pain need conservative treatment to be able to return to sport or their daily activities. On the other hand, because of this high inci- dence of anterior knee pain, prevention of this pathology has been an important goal for many sports medicine practitioners for some years. However, before a scientific approach in plan- ning and carrying out prevention and treatment of anterior knee pain can be set up, a thorough understanding of the etiology of anterior knee pain seems essential. This understanding refers to information on why a particular individual develops anterior knee pain and another indi- vidual, exposed to more or less the same exer- cise load, does not. In addition, it seems important to understand why some patients benefit from a treatment program while others do not, or not as well. To answer these impor- tant issues risk factors for the development of anterior knee pain need to be identified. General consensus exists about the fact that myriad factors may contribute to the develop- ment of anterior knee pain. Anterior knee pain can be considered as a multi-risk phenomenon with various risk factors interacting at a given time. 32 Risk factors are traditionally divided into two main categories: intrinsic (or internal) and extrinsic (or external) risk factors. The extrinsic risk factors relate to environmental variables, for example, exercise load, exercise intensity, exercise type, amount of physical activity, equipment, weather conditions, and playing field conditions. In contrast, intrinsic risk fac- tors relate to the individual physical and psy- chological characteristics such as age, joint instability, gender, muscle strength, muscle flexibility, conditioning, and so forth. Focusing on injury prevention requires the use of a dynamic model that accounts for the multifactorial nature of anterior knee pain. One such model is described by Meeuwisse. 32 This model describes how multiple factors interact to produce an injury (Figure 8.1). It can be seen in this model that numerous intrinsic factors theo- retically may predispose an individual to ante- rior knee pain. This model also shows very well the interaction of both intrinsic and extrinsic factors, in the way that the extrinsic risk factors act on the predisposed athlete from outside. Consequently, knowledge of both the intrinsic and extrinsic risk factors of anterior knee pain seems essential in our understanding of the eti- ology, and thus in creating prevention and con- servative treatment programs. The Role of Extrinsic Risk Factors in the Development of Anterior Knee Pain The association between clinical overload (external risk factors) and the development of anterior knee pain is well known. 14,34 Recently, 135 8 Risk Factors and Prevention of Anterior Knee Pain Erik Witvrouw, Damien Van Tiggelen, and Tine Willems