Is Femoroacetabular Impingement Congenital or Acquired?
Femoroacetabular impingement (FAI) is primarily an acquired condition that develops during skeletal growth, particularly during adolescence, rather than being truly congenital. The current evidence strongly suggests that FAI morphology develops through repetitive mechanical stress during critical periods of bone development, especially in athletes participating in high-impact sports 1, 2.
The Developmental Pathway
Acquired During Growth (Most Common)
The most compelling evidence points to cam-type deformities developing through repetitive injury to the proximal femoral physis during adolescence 1. This mechanism explains why:
- High-volume impact activities during skeletal maturity are strongly correlated with cam morphology development
- Elite athletes in football, ice hockey, basketball, and soccer show significantly higher prevalence of FAI 1
- The condition manifests during the critical period of physeal closure when the growth plate is most vulnerable to mechanical stress 2
Mixed Etiology
While genetic factors have been studied, there is no conclusive evidence that FAI is transmitted genetically 1. The etiology appears multifactorial:
- Environmental factors (sports participation, repetitive loading) play the dominant role
- Biomechanical influences from lumbar spine, pelvis, and femoral alignment contribute to dynamic impingement 2
- Some genetic susceptibility may exist, but this is not the primary driver 1, 2
Clinical Implications
Understanding FAI Syndrome
According to the 2020 International Hip-related Pain Research Network consensus, FAI syndrome is defined as a motion-related clinical disorder resulting from repetitive mechanical loading between the femoral head and acetabular rim 3. This loading pattern:
- Contributes to acetabular labral damage
- Causes chondrolabral findings
- Leads to early osteoarthritis 3
The Three Types
FAI presents in three morphological patterns 4:
- Cam type: Aspherical femoral head (acquired through repetitive stress)
- Pincer type: Acetabular overcoverage (may have developmental component)
- Mixed type: Combination of both
Key Clinical Pitfalls
Do not assume FAI is present from birth. The morphological changes typically develop during:
- Adolescent growth spurts
- Periods of intense athletic training
- The window of physeal closure (ages 10-16 typically)
Recognize that imaging findings alone do not equal disease. The 2020 consensus emphasizes that incidental intra-articular findings are common in asymptomatic individuals and diagnosis should never be made on imaging alone 3. FAI syndrome requires the triad of symptoms, clinical signs, AND imaging findings 3.
Prevention Considerations
Since FAI is primarily acquired during development, monitoring adolescent athletes participating in high-impact sports during skeletal maturity may identify at-risk individuals 1, 2. However, specific preventive strategies remain under investigation 5.
The molecular similarities between FAI cartilage and osteoarthritic cartilage suggest that once established, the condition follows a degenerative pathway 2, making early identification during the developmental phase potentially valuable for long-term joint preservation.