Recent concept. Common cause of hip pain in young adults.
Proposed to be one of the causes of arthritis of the hip at younger age.
What are the mechanisms?
Cam impingement (bony bump at the head neck junction damages the labrum and cartilage
Pincer impingement (over-coverage of the acetabular wall – the labrum gets pinched
between the acetabulum and femoral neck and gets damaged)
What are the symptoms?
FAI usually presents in active young adults with slow onset of deep groin pain that
may start after a minor trauma. During the initial stages of the disease, the pain
is intermittent and may be exacerbated by excessive demand on the hip, such as from
athletic activities including deep flexion of the hip or prolonged walking. The pain
also may present after sitting for a prolonged period.
Mechanical symptoms from the hip such as painful locking or giving way are common
presenting feature if labral tear is present.
Whom does it affect?
Cam impingement – more common in young active males (M:F 14:1, age range 21-51, mean
Pincer impingement – More common in middle-aged active females (M:F 1:3, age range
40-57, mean 40)
(TannastM, SiebenrockKA, AndersonSE. Femoroacetabular Impingement:
Radiographic Diagnosis—What the Radiologist Should Know AJR
Often many have mixed type of impingement
What are the clinical signs?
Anterior Impingement test - Hip is flexed to 90 degrees. Hip then passively flexed
further, adducted and internal rotation – Positive if it reproduces the pain similar
to that experienced by the patient.
Posterior impingement (uncommon) – The hip is passively hyperextended by hanging
the leg over the end of the couch while keeping the opposite limb in neutral position.
Pain is reproduced if passive external rotation of the extended leg.
Differential diagnosis of hip pain in young adults
Snapping iliopsoas tendon
Non hip causes like inguinal hernia etc.,
How do we investigate?
Cam impingement: Bump over the anterolateral aspect of the femoral neck. Often obvious
only in the horizontal beam lateral – hence the need to do both AP pelvis Xray and
horizontal beam lateral when impingement syndrome is suspected. Various measurements
like alpha angle etc.,
Pincer impingement: Cross over sign in standardised AP pelvis Xray – due to overcoverage
of the anterior acetabular wall.
MRI arthrogram – evaluates cartilage damage and labral tear. Also may show pathology
like avascular necrosis.
An initial trial of nonsurgical treatment, which may include activity modification
including restriction of athletic activities, and nonsteroidal anti-inflammatory
medications. Physical therapy with an emphasis on improving passive range of motion
or stretching may be counterproductive and exacerbate the symptoms.
1. Through open dislocation of the hip
2. Combined arthroscopy and mini-open approach
3. Arthroscopic treatment
Encouraging early results for symptomatic improvement in recent literature.
Less optimal result when there is large area of cartilage damage or presence of early
Still an evolving concept
No long term studies are available to show that surgical treatment can prevent the
progression of arthritis