Editor: Vicente Sanchis-Alfonso, MD, PhD
The term patellofemoral pain refers to pain perceived in the anterior aspect of the knee following exclusion of other objective causes of anterior knee pain. Anterior knee pain is the most common knee complaint seen in adolescents and young adults, in both the athletic and nonathletic population, although its incidence is higher in the athletic population. The prevalence is around 9% in young active adults. It accounts for 5.4% of total pathology and as much as a quarter of all knee problems treated at a sports injury clinic. Females are particularly predisposed to it. Anatomic factors such as increased pelvic width and resulting excessive lateral thrust on the patella, and postural and sociological factors such as wearing high heels and sitting with legs adducted can influence the incidence and severity of this condition in women. Anterior knee pain is a nemesis to both the patient and the treating physician, creating chronic disability, limitation from participation in sports, sick leave, and generally diminished quality of life.
Melzack and Casey proposed structuring pain in three dimensions: (1) sensory-discriminative - it refers purely to the sensitive magnitude of pain, with which we can determine three related elements: its location, its intensity and its quality; (2) affective-motivational - it refers to the emotional properties that accompany the painful feeling such as fear (or anxiety), sadness (or depression), rage or anger that facilitate or predispose for a response such as aversion, escape, avoidance or fight; and (3) cognitive-evaluative - it refers to beliefs, thoughts, attitudes and coping strategies regarding pain, the consequences of the experience of pain and the possible design of a conscious plan to handle the situation. These categories interact with one another and influence each other, and can only be understood as a whole.
Traditionally pain has been related to the disability that the person with a lesion suffers. This correlation is very strong in acute pain. For example, a patient with an acute patellar dislocation experiences acute pain limiting his mobility and disabling him for his ordinary activities. However, chronic pain, as occurs in patellofemoral pain patients, and disability are independent variables with a poor correlation. Anterior knee pain patients show different degrees of disability in their everyday life, regardless of how intense the pain is.
Moreover, no significant correlation between severity of structural alterations of the patellofemoral joint and disability and pain have been observed in all the cases. For instance, patients with important anatomic alterations (patellofemoral malalignment, severe patellar chondropathy) may be painless, while patients with minimal structural changes can be very symptomatic (pain or disability).
For more than a century the treatment of musculoskeletal conditions has been based on a biomedical disease model that establishes direct relationships between tissue damage, pain, and disability. Therefore, the doctor´s task would be to repair the damage and clear the pain, making the functional impairment and disability disappear. This model has worked well for conditions such as patellar instability. However, for some conditions that develop with chronic pain, such as anterior knee pain or patellofemoral pain, this classical model is not enough to establish an adequate understanding of the pain and impairment process associated with the disease. In these cases, a biopsychosocial model that integrates patients´ biological, psychological and social elements would be more useful.
It has recently been suggested that fear avoidance (kinesophobia) and catastrophizing ideas are related to pain chronification and disability in other musculoskeletal conditions such as lumbar pain. It is possible that these factors are partially responsible for disability and pain chronification in patellofemoral pain patients as well. This possibility has not been studied in the literature. The biopsychosocial model may allow the development of more adequate therapeutic strategies than the biomedical model in the case of patellofemoral pain.
So, we are going to analyze anterior knee pain from a biologic, structural-biomechanical, and psycho-social perspective.
Vicente Sanchis-Alfonso, MD, PhD
Towards a Better Understanding of Anterior Knee Pain: Donīt Forget to Look Up
Pathophysiology of Anterior Knee Pain
(The full text is available from the Springer website at http://www.springer.com/medicine/orthopedics/book/978-3-642-05423-5?changeHeader)