What is Femoroacetabular Impingement (FAI)?

FAI is essentially a mismatch between the shape of the ball and socket of the hip joint, causing the two to make contact when they shouldn’t. The abnormal contact causes damage to the ball (femoral head), the socket (acetabulum), and the labrum (a ring of rubber-like cartilage that lines the socket). The abnormal contact, called impingement, also causes pain in the hip joint.

What causes FAI?

FAI is caused by a misshapen ball, socket, or both.

Pincer Lesion: A misshapen socket is called a “pincer lesion.” The socket must cover the ball in just the right amount to provide stability and allow enough motion. If the socket is too deep, if it points the wrong direction, or if it covers too much of the ball, the ball will collide with the edge of the socket, even within a normal range of motion.

Cam Lesion: A misshapen ball is called a “cam lesion.” In order for the ball to move through a large range of motion, it must be a sphere, and it must have a large diameter which then narrows quickly into a skinny shaft (neck) so that it won’t impinge on the edge of the socket. This difference in diameter allows the ball to move freely. If the neck is too broad, and the difference between the diameter of the head and neck is too small, they will impinge on the edge of the socket.

Combined: Many people will have both a cam and pincer lesion.

Labral tear: The labrum is a rubber-like ring of cartilage attached to the circular edge of the hip socket. It creates a fluid-tight seal around the edge of the socket, maintaining a frictionless environment between the ball and socket and providing some stability to the joint. When the ball and socket impinge, the labrum gets crushed and torn. Sometimes the labrum tears in the center of its own tissue, but it is more common for it to tear away from the bony edge of the socket. Either type of tear causes pain and loss of labral function. This endangers the cartilage within the joint, leading to early onset arthritis.

I’m only a teenager. Why do I have FAI?

Most likely you are a young, very competitive athlete. You work your joint more vigorously than other people your age, and the constant abnormal contact causes early symptoms. This is what we call an overuse injury. Months and years of pushing this joint to its limit has taken its toll.

What does FAI feel like?

FAI usually feels like a sharp pain deep in the groin area or in the front of the hip. It worsens with athletic activities, or with prolonged sitting. As symptoms progress, the muscles surrounding the hip will fatigue and become very sore. This can feel sharp or dull, and can be located at the side of the hip, in the lower back or buttocks. You may also experience popping, painful or not. Sometimes the pain will even happen with normal activities like walking or going up and down the stairs.

What should I do?

Pay close attention to the activities that cause the most pain. If you can avoid those activities, you should. As mentioned above, most of you are athletes, and you love playing your sport. You don’t want to quit. That’s okay, we would feel the same way. But be careful, the longer you play with pain, you could be causing significant damage to the inside of the hip.

Over the counter medications, such as ibuprofen and naproxen, can help. Use them as directed. Ice, heat, and massage may also help the symptoms. None of these things treat the underlying cause, but they can help you in the short term to feel better.

It still hurts. Whom should I talk to?

You need to see a pediatric orthopedic surgeon who sub-specializes in the treatment of FAI. We will ask you several questions to better understand your pain.

Exam of the hip: our clinicians will examine your hip, knees, and back to determine the source of your pain. I will put your hip through a range of motion and perform tests to see where the pain is coming from. The impingement test is a way to maneuver the hip that will help us understand if FAI is a likely cause of your pain.

X-rays: An x-ray of your pelvis will be reviewed, with an additional x-ray which shows the profile of the hip. This is the BEST way to evaluate the shape of the ball and socket.

MRI (magnetic resonance imaging): If your history, exam, and x-rays indicate you have FAI, an MRI of the hip may be ordered to further assess the extent of the damage. This test is the best way to look at the labrum to see if it is torn and damaged. The MRI requires an injection of fluid into the hip. This helps us in two ways. First, it is the best way to see the labrum. Second, a numbing medication is put into the hip as part of the fluid. The medication works for an hour or two. If your pain significantly improves during that time, we can conclude you pain is indeed coming from the hip joint.

What can I do about my FAI?

Non-surgical treatment: Non-surgical treatment consists of the options mentioned above in the section “What should I do?” In addition, you will visit a physical therapist. The therapist will help you strengthen the large muscles around the hip. This may relieve some of the stress on the injured labrum and cartilage, resulting in decreased pain.

Surgical treatment: If your history, physical exam, x-rays, and MRI all support the diagnosis of FAI, and non-surgical management fails, you may be a candidate for surgery. The surgery will address all deformity, and will repair the labrum.

There are two goals with surgery. In the short term, the goal is pain relief and return to sports. In the long term, there is some evidence that surgery could prolong the life of your hip. This is done by repair the damage to the labrum and cartilage.

The recommended surgery will depend on the exact type of FAI you have. The three main surgical options include: hip arthroscopy, surgical dislocation of the hip, and periacetabular osteotomy (re-orientation of the socket within the pelvis).

  • Hip arthroscopy: with hip arthroscopy, I can treat cam lesions, pincer lesions, combined lesions, and labral tears. During the surgery, two small incisions are made around the hip. Through these incisions, we place a camera and the tools needed to reshape the ball and socket. We can also repair the labrum using special stitches that anchor the labrum back to the bone.
  • Surgical dislocation of the hip: In cases of severe deformity on the ball side of the joint, hip arthroscopy may not be able to fix the problem. Surgical dislocation of the hip is a safer way to expose and correct larger deformities. It can treat the same issues as the hip arthroscopy, including cam and pincer lesions, and labral tears.
  • Periacetabular osteotomy: In cases of severe deformity on the socket side of the joint, the entire socket will need to be re-oriented. Again, this is a more invasive surgical procedure compared to hip arthroscopy. Because of this, we are very careful to ensure that we select the most appropriate surgery to address your specific hip problem.

At Rocky Mountain Pediatric Orthopedics, we have extensive experience with evaluating hip pain, determining its cause, and selecting the appropriate treatment as well as extensive experience with the three surgeries outlined above.

Our clinicians will take the time needed to explain all of this to you in our office visits, and to answer all of your questions and concerns. We understand surgery is a big deal. If you need it, we will take whatever time it takes to walk you through the process.