FAI
The hip is a ball and socket joint. The ball is the top of the thigh bone (femur) called the femoral head and the socket is the part of the pelvis called the acetabulum. Articular cartilage covers both the ball and the socket, serving to reduce friction which allows for smooth joint movement. FAI (femoroacetabular impingement) is a common hip joint disorder in young, active patients caused by a structural problem in the hip, specifically abnormal bone growth, leading to irregular contact between the femoral head and acetabulum. 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, the socket, or both. These irregularities cause 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, Pincer impingement, or both. CAM type impingement is caused by the abnormal shape of the femoral head and neck, which demonstrates a bump at the junction between the head and the neck. Pincer type impingement is caused an abnormal shape of the acetabulum in which the socket demonstrates excessive overhang. In some cases, both types can co-exist.
The friction and pressure caused by the changes seen in FAI can lead to hip joint damage over time, including bone spurs, tearing of the labrum, and hip osteoarthritis. Early diagnosis of hip impingement by a hip impingement specialist is crucial to minimize these long-term effects.
Surrounding the hip socket is a ring of tissue known as the hip labrum. The labrum provides additional stability to the joint. The hip labrum plays an important role in maintaining normal hip function, serving to tighten the seal between the bones adding stability to the joint, which allows for a wide range of motion and helps to maintain the alignment between the bones. When this tissue is damaged by an injury, degenerative change, or FAI, a hip labral tear can occur. 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 observed in FAI may result from a developmental deformity or can be acquired, meaning caused by injury or repetitive movements. Hip deformities and abnormal growth of bone on the ball and/or the socket can alter normal biomechanics, leading to hip labrum injury and accelerated degeneration of the hip joint. FAI may not cause symptoms until the hip is overused through activities that involve repetitive hip motions or the hip is pushed beyond its 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
Physical Exam
After obtaining a complete medical history, including discussion of symptoms and past injuries, a thorough physical exam is performed. The examination evaluates range of motion including flexion, adduction, and rotation to diagnose hip impingement. Hip impingement testing will also be performed during the physical exam. This test involves flexing the hip to bring the knee to the chest while the knee is rotated 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 helps 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 CT scan is usually not necessary but may be ordered in some cases 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 or x-ray guidance. If most of the pain goes away, even temporarily, following the injection, then it confirms that the source of the pain is due to FAI.
At a Glance
Meet Our Team
- Nationally Renowned Orthopedic Surgeons
- Double Board-Certified, Fellowship-Trained
- Previous Medical Staff for the NFL, NBA, MLB, NHL, MLS, PGA and Olympics
Meet Dr. Nima Mehran
Meet Dr. Matt Muffly
