Femoral Acetabular Impingement

What is Femoroacetabular Impingement?

Most recently FAI has been recognized as a cause of hip pain. FAI can be a source of hip pain at any age. FAI occurs when the femoral head and acetabulum have an abnormal contact, resulting in damage to the labrum/and or acticular cartilage, as well as limited range of motion in the hip joint. FAI is commonly classified into 3 forms. They are known as Cam impingement deformity, Pincer impingement deformity, or mixed impingement deformity resulting in a combination of the two. These are clearly seen in the photos below.

In a Cam impingement there is an abnormal contour of the femoral head-neck junction, resulting in impingement against the acetabulum.

Pincer impingement is caused by an acetabular abnormality, typically anterior, resulting in overcoverage of the femoral head. This could be an isolated bony protrustion or a degree of acetabular retroversion.

A Mixed type of FAI is a combination of both Cam and Pincer impingement deformities. This type of deformity has been associated with progressive joint degeneration.

Etiology of FAI

Femoroacetabular impingement is linked to childhood hip disorders such as Legg-Calve-Perthes Disease, Slipped Capitol Femoral Epiphysis, hip dysplasia, septic hip, and fractures. The majority of FAI cases are of unclear etiology, with some theories of physical stresses placed on the femoral head and /or acetabulum during development may contribute to the onset of FAI.

Diagnosis of FAI

Diagnosing of FAI starts from a good subjective history. Typically patients will complaints of hip-groin or back pain. Other complaints may include “ I can’t do that or move into that position.” Plain film X-rays are most commonly used to view the bony changes of the femoral head and acetabulum. A MRI or MR-arthrogram may also be used in diagnosing secondary injuries such as chondral lesions and/or labral tears. Most patients with FAI are capable to completing their daily tasks, but have difficulty and pain with high demand/impact type sports and/or activities. Typically there is no rest or night pain. Pt. will reports a lack of ROM in the hip, and demonstrate a “C” sign. Flexion, internal rotation and adduction are the most limited ranges of motion affected.

Differential Diagnosis

Patients with FAI are often misdiagnosed early on and potentially treated for a variety of diagnosis such as back pain, hip pain, groin pain, bursitis, piriformis syndrome, apophysitis, iliopsoas tendonitis, and “growing pain.”

Treatment of FAI

FAI can be managed surgically, although non-operative care can also be successful. The surgical approach will alter the bony changes, while the non-surgical approach can normalize soft tissue length, joint capsule mobility, strength, and education of overall joint preservation techniques. The success of conservative care of FAI is largely dependent of the patients willingness to modify their sport/activity. Surgical treatment is aimed at alterating the bony changes as well as the secondary injuries such as the chondral lesions and labral tears. Post-operative rehabilitation is dependent on the procedure performed. Typically, recovery from most FAI surgical procedures is 3-6 months, with the expectation that the patient is then able to return to full, unrestricted activity/sport.


FAI is a diagnosis that we are seeing more of each year, from a combination of better awareness, diagnostics, and its presentation. It is often misdiagnosed early on, and this can affect the management of these patients. Early diagnosis is important for how we treat these patients and the critical long term health of their hip joint. The ultimate goal is to allow for active healthy living.

By |2017-05-22T20:31:04+00:00March 18th, 2014|Hip, Orthopedic Disorders and Treatment|Comments Off on Femoral Acetabular Impingement