What is Femoroacetabular Impingement (FAI)?
The hip is the largest ball and socket joint in the body. It is formed by an articulation of the femoral head within the acetabulum and is stabilized by the larbum (which helps deepen the socket) and surrounding ligaments (iliofemoral, pubofemoral and ischiofemoral ligaments).
Femoroacetabular impingement (FAI) is characterized by bony maladaptation that results in anterior hip pain or discomfort when hip is flexed (i.e. sitting) or extended (i.e. hip extension in end of stance phase).
There are 3 different anatomical presentations found in individuals with FAI:
1) Cam: bony overgrowth on femoral neck, usually on anterior/superior aspect, causing impingement symptoms when there is flexion and internal rotation at the hip
- This overgrowth can initially develop as a protective mechanism in response to repetitive loading, especially in boys who start sport at an early age. A study found that 64% of boys who began sport before the age of 12 years developed some sort of cam morphology (Tak et al., 2015).
2) Pincer: extended or deepened acetabular rim overhanging anteriorly over femoral head and is more commonly found in females.
3) Mixed: bony articular adaptations that involve both characteristics, femoral neck and acetabular.
Although many cases of bony morphology in the hip are asymptomatic, the earlier in life that an individual begins a pattern of continuous repetitive loading, the greater the risk of developing painful FAI and other hip pathologies later on in life.
Conditions that may be related
- Hip OA
- Labral pathology
- Synovitis
- Hip tendinopathy
- Kinetic chain effects (i.e. secondary knee pathology)
Common symptoms / signs
- Deep, localized anterior hip pain – worse with loaded activities in flexion and extension
- Aggravated by hip flexion movements (sitting cross legged, stairs, kicking) and repetitive hip extension movements (such as end stance gait, kicking)
- Difficulty with tasks requiring single leg balance
- X-ray: Dunn 45º view
o alpha angle >60 º = positive cam deformity
How is it treated?
Currently, there is a lack of consistent literature outlining best management. The Warwick agreement (an international consensus on diagnosis and management of FAI) suggests that treatments for FAI include conservative treatment (education, lifestyle and activity modification), physiotherapy (neuromuscular control, improving ROM, strengthening, balance and movement retraining) and surgery. While surgery is an option to remove lesions and repair labrums, studies have shown that there is no significant long term benefit of surgery over physiotherapy (Mansell et al., 2018).
Considering that cam morpohology is a protective adaptation that results from poor positioning and hip control, conservative treatment using physiotherapy should aim to treat physical assessment findings and impairments. Findings often include reduced hip muscle strength, reduced hip motor control, decreased balance and impairments in trunk function.
Exercise interventions should aim to activate and strengthen deep stabilizers of the hip, particularly the posterior muscles (i.e. glute minimus/medius, obturator internus, quadratus femoris and the gemelli) which aid in external rotation, extension and abduction at the hip. This will help to draw the femoral head more posteriorly into the acetabulum, reducing impingement to the anterior aspect of the femoral neck that results in pain and discomfort.
Some examples of exercises:
- Isometric external rotation in prone
- Side lie hip abduction (<45deg for glute medius)
- Standing hip abduction
- Glute bridge (DL à SL)
- SL knee drives
- Bulgarian split squat
- Bird dog
Risk factors of this condition?
- Past history of paediatric hip conditions (such as SUFE or Perthes disease)
- Family history of congenital hip conditions
- Sport at young age
Other causes?
- Fracture of femur
- Avascular necrosis of femoral head
- Hip dysplasia
- Hip OA
- Labral pathology
- Inguinal pathology
- Adductor tendinopathy
- Pubic stress response
References
Griffin, D. R., Dickenson, E. J., O’donnell, J., Awan, T., Beck, M., Clohisy, J. C., … & Bennell, K. L. (2016). The Warwick Agreement on femoroacetabular impingement syndrome (FAI syndrome): an international consensus statement. British journal of sports medicine, 50(19), 1169-1176.
Mansell, N. S., Rhon, D. I., Meyer, J., Slevin, J. M., & Marchant, B. G. (2018). Arthroscopic surgery or physical therapy for patients with femoroacetabular impingement syndrome: a randomized controlled trial with 2-year follow-up. The American journal of sports medicine, 46(6), 1306-1314.
Tak, I., Weir, A., Langhout, R., Waarsing, J. H., Stubbe, J., & Kerkhoffs, G. (2015). The relationship between the frequency of football practice during skeletal growth and the presence of a cam deformity in adult elite football players. British journal of sports medicine, 49(9), 630-634.