What is Femoroacetabular Impingement (FAI)?

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From the Guidelines

Femoroacetabular impingement (FAI) is a condition where abnormal bone growths around the hip joint cause painful friction during movement, leading to damage of the labrum and articular cartilage, and is typically characterized by groin pain, stiffness, and limited range of motion 1.

Definition and Classification

FAI occurs when either the femoral head has extra bone that makes it less round (cam-type), or when the acetabulum has overgrowth that extends too far over the femoral head (pincer-type), or a combination of both 1.

Diagnostic Criteria

The diagnostic utility of clinical and diagnostic imaging examination in isolation is limited, and a comprehensive examination of patient symptoms, clinical signs, and diagnostic imaging is recommended 1.

Key Features

Some key features of FAI include:

  • Pain in the groin or front of the hip, especially during activities that require hip flexion like sitting, squatting, or athletic movements
  • Stiffness, limited range of motion, and a catching or locking sensation
  • Abnormal contact between the proximal femur and the acetabulum, leading to damage of the labrum and articular cartilage 1

Treatment

Treatment begins with conservative measures including activity modification, physical therapy focusing on core strengthening and hip mobility, and anti-inflammatory medications like ibuprofen or naproxen 1.

Surgical Options

If these fail to provide relief, surgical options include arthroscopic procedures to reshape the bones and repair damaged cartilage 1.

Quality of Life

Without treatment, FAI can lead to early osteoarthritis of the hip, significantly impacting quality of life, function, work capacity, and family life 1.

From the Research

Definition and Characteristics of Femoroacetabular Impingement (FAI)

  • Femoroacetabular impingement (FAI) is a chronic hip condition caused by femoral head and acetabular malformations resulting in abnormal contact across the joint 2.
  • FAI is characterized by premature contact of the femur and acetabulum during hip motion, leading to labral, cartilaginous, and tissue damage that predispose patients to early osteoarthritis (OA) 3, 2.
  • Morphologic variations of FAI present as either aspherical femoral deformity (cam femoroacetabular impingement) or overcoverage (pincer femoroacetabular impingement) or both 3, 2.

Symptoms and Diagnosis of FAI

  • Patients with FAI often describe discomfort with hip flexion, adduction, and internal rotation 3.
  • Slow-onset, persistent groin pain is the most frequent initial presenting symptom 2.
  • On physical examination, patients will typically have a positive FADIR test (flexion, adduction, internal rotation), also known as a positive impingement sign 2.
  • The primary imaging modality for diagnosing FAI is a plain radiograph of the pelvis, which can be used to measure the alpha angle and the lateral center edge angle used to quantify severity 2.

Treatment and Management of FAI

  • Conservative treatment is typically considered first-line treatment for mild to moderate FAI syndrome 2.
  • The use of hip arthroscopy to treat FAI has risen substantially over the last 15 years 3.
  • Sports medicine professionals often help patients with FAI explore nonoperative exercise strategies and direct rehabilitation exercises for those who pursue surgery 3.
  • Hyaluronic acid injections have been shown to be safe and effective in the treatment of mild femoroacetabular impingement, with significant pain reduction and function improvement 4.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Femoroacetabular impingement: is hyaluronic acid effective?

Knee surgery, sports traumatology, arthroscopy : official journal of the ESSKA, 2014

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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