FAI (femoroacetabular impingement) is a common hip joint disorder in young, active patients caused by a structural problem, specifically abnormal bone growth, that leads to irregular contact between the acetabulum and the femoral head. The hip is a ball and socket joint. The socket is the part of the hip bone called the acetabulum, and the head of the femur is the ball. Articular cartilage covers both the ball and the socket and functions to reduce friction for smooth joint movement. In a healthy hip, the ball of the femur fits perfectly into the acetabulum. However, in individuals with FAI, there may be irregularities in the shape of either the ball or the socket, or both. These irregularities cause hip joint impingement during activities like walking, running, or bending the hip, which can result in hip impingement symptoms such as groin pain and discomfort.
The location of the hip impingement can be described as either CAM impingement or Pincer impingement, or both. The CAM type is caused by the abnormal shape of the femoral head and neck, while the Pincer-type is caused an abnormal shape of the acetabulum. In some cases, both types can co-exist.
The friction and pressure caused by FAI can lead to further hip joint damage over time, including bone spurs, a labral tear, and hip osteoarthritis. Thus, early hip impingement diagnosis by a hip impingement specialist is crucial.
The hip labrum is a ring of cartilage that surrounds the hip socket, providing stability to the joint. The hip labrum plays an important role in maintaining normal hip function. It functions to tighten the seal between the bones for joint stability, allows for a wide range of motion and helps to maintain the alignment between the bones. A hip labral tear occurs when this cartilage is damaged or torn, often due to a hip injury, degeneration, or FAI. This tear can lead to a range of symptoms, including hip labrum pain (groin pain), clicking or catching sensations, and a decreased range of motion.
The bone abnormality of FAI may be a developmental deformity or acquired, meaning caused by injury or repetitive movements. Hip deformities and the abnormal growth of bone on the ball and/or the socket alter normal biomechanics and lead tohip labrum injury, and accelerated joint degeneration. FAI may not cause problems until the hip is overused through activities that involve repetitive hip motions or pushed beyond the hip’s normal range of motion.
Intermittent deep groin pain or ache (most common)
Pain at the outside of the hip joint
Sharp stabbing pain when twisting, turning or squatting, such as when getting in or out of a car or a chair
A dull ache from prolonged sitting or walking
A sensation of catching, clicking, or locking in the hip joint during movement
Instability of the hip joint
Stiffness and reduced flexibility in the hip joint
Limping
During your consultation with Dr. Jorge Chahla, a Chicago sports medicine surgeon and FAI specialist, your medical history, FAI symptoms, and past injuries will be reviewed.
Physical Exam
Dr. Chahla will conduct a physical examination checking range of motion including flexion, adduction, and rotation to diagnose your hip impingement. The hip impingement test will also be performed during your physical exam. This is a test in which Dr. Chahla will ask you to bring your knee to your chest while Dr. Chahla rotates the knee in toward the opposite shoulder (FADIR [flexion, adduction, and internal rotation]). If the hip impingement test causes pain, you likely have a hip labral tear. A comprehensive physical exam is key to determine the cause of your hip pain.
Imaging
Diagnostic imaging is necessary to definitively diagnose FAI and a hip labral tear. X-rays will reveal abnormally shaped bones, and an MRI will reveal damage to the soft tissue, such as the labrum (a hip labral tear). A CT scan is usually not necessary, but in some cases Dr. Chahla may order one, as it can provide details about the shape of the bones, location of abnormal bone growth, and the rotation of the bones.
Hip Injection
An intra-articular hip injection can help to confirm the diagnosis of hip impingement. This injection will be performed in the office at the time of your office visit under ultrasound guidance. If the majority of your pain goes away, even temporarily, following the injection, then it confirms that the source of the pain is due to FAI.
At a Glance
Dr. Jorge Chahla
Triple fellowship-trained sports medicine surgeon
Performs over 700 surgeries per year
Assistant professor of orthopedic surgery at Rush University
