Femoroacetabular impingement syndrome

FAIS is a motion-related clinical disorder of the hip with a triad of symptoms, clinical signs, and imaging findings. It represents symptomatic premature contact between the proximal femur and the acetabulum.

The pathophysiology of FAIS involves abnormal contact between the femoral head and the acetabulum due to bony abnormalities. This can lead to shearing forces at the acetabular labrum and cartilage during physiological hip motion, potentially causing cartilage wear and eventual osteoarthritis.

The epidemiology of FAIS remains largely unknown. Imaging findings suggestive of the syndrome are also prevalent in asymptomatic individuals, with a higher prevalence observed in athletes.

Risk factors include genetic predisposition, participation in certain sports, and developmental hip disorders, such as hip dysplasia or Perthes disease.

Clinically, patients with FAIS often present with motion- or position-related pain in the hip or groin. Pain may also be felt in the back, buttock, or thigh. They may also describe clicking, catching, locking, stiffness, limited ROM (typically restricted internal rotation in flexion), or giving way. In addition to these symptoms, patients with FAIS may demonstrate altered gait mechanics and hip joint loading.

The prognosis of FAIS can vary widely and is influenced by factors such as the type of FAIS (cam, pincer, or mixed), the extent of cartilage and labral damage, and the timing and type of intervention. Treatment often leads to symptom improvement, allowing patients to resume full activity, including sports. Without treatment, symptoms of FAIS typically worsen over time. Cam morphology is associated with the development of hip osteoarthritis.