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CURRENT CONCEPTS

Femoroacetabular Impingement
The physical exam usually demonstrates decreased
internal rotation. The most important finding is the anterior

impingement sign (Fig 1). It is considered positive when it
elicits anterior hip pain during flexion, adduction and internal

rotation. It is also important to clear spine pathology and
inguinal hernia, because these conditions may mimic FAI.

Leandro Ejnisman, MD
Classification
FAI is classified in 3 types: cam, pincer and mixed-type.

Cam impingement refers to the femoral side. The femoral
head-neck junction has a bony “bump”, and this bump

impinges on the acetabular rim as the hip is flexed and
internally rotated. The labral tissue can be detached at the
Additional Author:
Robert F. LaPrade, MD, PhD, USA chondrolabral junction. An acetabular cartilage flap can be
seen adjacent to the labral tear.
ISAKOS Sports Medicine Committee
Pincer impingement refers to bony impingement on

Introduction
the acetabular side. It can be caused by global or focal
overcoverage of the femoral head. Global overcoverage
Femoroacetabular impingement (FAI) is a common cause of occurs in cases of coxa profunda and protrusio acetabuli.
hip pain in the athlete. It is important for a sports medicine
Normally, the acetabular floor is lateral to the ilioischial line.
physician to be able to diagnose and treat this condition In cases of coxa profunda, the acetabular floor is medial to
because a delay in the diagnosis can lead to a longer period
the ilioischial line. In cases of protrusio acetabuli, the femoral
of recovery and return to sport. Moreover, FAI is a cause for head is medial to the ilioischial line. Focal overcoverage
early hip osteoarthritis; and early intervention is indicated in
is seen in cases of acetabular retroversion. In pincer
order to avoid severe chondral damage.
impingement, the labrum is usually degenerated and labral

Clinical Presentation
cysts can be found.

Patients typically present with inguinal pain, which might The most common type of FAI is the mixed-type, representing
present with traumatic or insidious onset. The pain may 75% of patients. Pincer and cam characteristics co-exist in

also be referred to the lateral thigh, inner thigh and buttocks. the same patient. On the femoral side, a high alpha angle
Activities involved in this condition are sports with a rotational is found, and on the acetabular side, overcoverage signs
are present. Surgical findings can demonstrate a bruised
demand on the hip, such as soccer, ice hockey, football,
rugby and skiing. Patients frequently complain about pain or degenerated labrum, which might be detached from the
acetabular rim, suggesting a mixed pattern of labral injury.
during prolonged sitting.

Imaging
Radiographs are of paramount importance in FAI

investigation. Many physicians neglect their use, and
order only a MRI. The x-ray will often evaluate the hip bony

morphology better than the MRI. Proper position during
radiographs is essential because minor pelvic inclination may

alter FAI radiographic findings.

The anteroposterior pelvic x-ray is evaluated. One must
look for signs of pincer impingement. The cross-over sign

is diagnostic of focal overcoverage. The acetabular walls
should cross in the lateral aspect of the acetabulum. When

the cross-over sign is present, the posterior and anterior
wall cross before the lateral aspect of the acetabulum. The
acetabular center-edge angle is measured, as well as the

joint space.

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ISAKOS NEWSLETTER 2014: Volume II 27