Risk factors and prevention of anterior knee pain

Anterior knee pain (AKP) is known as a very common problem in the sporting population. ^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 incidence 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 planning 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 individual, exposed to more or less the same exercise 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 important 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 development 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 factors relate to the individual physical and psychological 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 theoretically may predispose an individual to anterior 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 etiology, and thus in creating prevention and conservative treatment programs.