Femoroacetabular Impingement (FAI): Signs, Symptoms, and Diagnosis

What are the Signs of FAI?

Femoroacetabular Impingement (FAI) is a condition characterized by abnormal contact between the femoral head/neck and the acetabular rim, leading to hip pain and restricted movement. Recognizing its signs is crucial for timely diagnosis and intervention.

Understanding Femoroacetabular Impingement (FAI)

Femoroacetabular Impingement (FAI) occurs when the bones of the hip joint are abnormally shaped, causing them to rub against each other during movement. This repetitive friction can damage the articular cartilage and the labrum—the cartilage ring that cushions the hip joint—leading to pain, stiffness, and potentially early onset osteoarthritis.

There are three primary types of FAI, often occurring in combination:

• Cam Impingement: An excess of bone around the head and neck of the femur (thigh bone), which grinds against the acetabulum (hip socket) during hip flexion and internal rotation.
• Pincer Impingement: An overgrowth of the acetabular rim, which pinches the femoral head and labrum. This can be localized or generalized (coxa profunda, protrusio acetabuli).
• Mixed Impingement: A combination of both cam and pincer deformities, which is the most common presentation.

Primary Symptoms of FAI

The signs and symptoms of FAI typically develop gradually and may worsen with specific activities.

• Pain: This is the most common symptom.
  • Location: Primarily felt in the groin area, often described as a deep ache. Pain can also radiate to the outer hip (lateral hip), buttock, or even down the thigh.
  • Character: Can range from a dull ache to a sharp, stabbing pain, especially with certain movements.
  • Aggravating Factors: Pain is often provoked by activities involving deep hip flexion, internal rotation, or prolonged sitting. This includes movements like squatting, lunging, pivoting, getting in and out of a car, or even tying shoes.
• Stiffness and Restricted Range of Motion: Individuals with FAI often experience a noticeable reduction in hip flexibility, particularly in movements like hip flexion and internal rotation. This stiffness may be more pronounced after periods of inactivity.
• Clicking, Catching, or Locking Sensations: Mechanical symptoms within the hip joint are common. A clicking or popping sound may be heard or felt during movement. A catching sensation indicates something is momentarily getting "caught" within the joint, while locking implies a temporary inability to move the hip joint. These sensations often suggest associated labral damage.
• Limping: In some cases, especially as the condition progresses or pain becomes more severe, a slight limp may develop as the body attempts to offload the affected hip.

Common Activities That Provoke FAI Symptoms

Certain movements and activities are notorious for exacerbating FAI symptoms due to the increased impingement they cause:

• Prolonged Sitting: Especially in low chairs or car seats, which keep the hip in a flexed position.
• Deep Squatting or Lunging: Common in weightlifting, yoga, or daily activities like gardening.
• Pivoting or Twisting Movements: Activities like golf, martial arts, dance, or sports requiring rapid changes in direction (e.g., soccer, hockey, basketball).
• Getting In and Out of a Car: The combination of hip flexion and rotation can be particularly painful.
• High-Impact Sports: Running, jumping, and other activities that place repetitive stress on the hip joint.

Differentiating FAI from Other Hip Conditions

The symptoms of FAI can overlap with other hip pathologies, making accurate diagnosis critical. Conditions that may present similarly include:

• Labral Tears: While often co-occurring with FAI, a labral tear can also happen independently.
• Hip Osteoarthritis: Degenerative joint disease, which FAI can accelerate.
• Greater Trochanteric Pain Syndrome (Bursitis): Pain on the outside of the hip.
• Adductor Strain: Pain in the inner thigh.
• Referred Pain: Pain originating from the lumbar spine (lower back) or sacroiliac joint can be felt in the hip or groin.

A thorough clinical examination and diagnostic imaging are essential to differentiate FAI from these other conditions and to confirm the diagnosis.

Clinical Examination and Diagnostic Signs

A healthcare professional, such as an orthopedic surgeon or physical therapist, will perform specific tests to evaluate for FAI:

• Physical Examination:
  • Impingement Tests (e.g., FADIR Test): The FADIR (Flexion, Adduction, Internal Rotation) test is highly sensitive for FAI. The hip is flexed to 90 degrees, then adducted (moved across the body) and internally rotated. Pain during this maneuver suggests impingement.
  • FABER Test (Flexion, Abduction, External Rotation): While less specific for impingement, this test assesses hip mobility and can reproduce pain if there is anterior hip pathology.
  • Assessment of hip range of motion, gait, and muscle strength.
• Imaging:
  • X-rays: Used to visualize the bony abnormalities characteristic of cam and pincer impingement, such as the alpha angle (for cam) and acetabular retroversion (for pincer).
  • Magnetic Resonance Imaging (MRI) or MR Arthrography: Provides detailed images of the soft tissues, including the labrum and articular cartilage, to detect tears or damage.
  • Computed Tomography (CT) Scan: Can offer a more precise 3D view of the bony anatomy and deformities.

When to Seek Medical Attention

If you experience persistent hip or groin pain, especially if it is aggravated by the activities described above, and is limiting your daily function or exercise, it is important to consult a healthcare professional. Early diagnosis and management of FAI can help alleviate symptoms, prevent further joint damage, and improve long-term hip health.

Conclusion

Recognizing the signs of Femoroacetabular Impingement—primarily groin pain provoked by deep hip flexion and rotation, accompanied by stiffness or mechanical symptoms—is the first step towards effective management. While these signs are indicative, a definitive diagnosis requires a comprehensive evaluation by an orthopedic specialist, integrating clinical examination findings with advanced imaging. Timely intervention, whether through conservative management or surgical correction, is key to preserving hip function and mitigating the progression of hip osteoarthritis.