The prevalence of radiological FAI is a common finding in asymptomatic active individuals (1). Three types of morphological variations have been described in FAI: Cam, Pincer and mixed. Fortunately, very few develop clinical symptoms and current evidence does not support prophalytic screening for FAI in the asymptomatic population (2). A radiological finding of FAI is not sufficient for the diagnosis of FAI, since it is a clinical diagnosis, based on clinical history, physical examination and relevant imaging.
So, how do you define symptomatic FAI?
A recent consensus meeting defined FAI as “ a clinical entity in which a pathological mechanical process causes hip pain when morphological abnormalities of the acetabulum and/or femur, combined with vigorous hip motion (especially at the extremes), lead to repetitive collisions that damage the soft-tissue structures within the joint itself. ” (3).
Let us examine some contributing factors which have been linked with the aetiology of FAI in the active population.
Genetic Factors
It has been reported that the relative risk of having a cam or pincer deformity in siblings of patients with cam or pincher type FAI is nearly three times (4). Another study had shown that the morphological evidence of FAI was more common in white women as compared to Chinese women (5). Further, the prevalence of cam deformity is higher in men compared with women (6). These studies suggest there could be a genetic influence, leading to the development of FAI.
Developmental Factors
It has been shown that cam-type deformity develops around the age of 10-12 years (7) and does not progress after the closure of the growth plate in the athletic population (8). Therefore, one can assume that cam type deformity is related to skeletal development. Further, there is a link between training intensity and frequency with the radiological signs of FAI. Athletes with excessive participation in high-impact athletic activities such as football, ice hockey and basketball during adolescence when the skeleton is maturing have a higher incidence of FAI (9-11). It is believed that the high shear forces at the antero-superior head-neck junction of the growing hip leads to changes in the shape of the growth plate.