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Femoroacetabular Impingement (FAI)

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What is Femoroacetabular Impingement?

Femoroacetabular impingement, or FAI, is a condition where extra bone grows in the area of your hip joint. As a result, your bones can touch and pinch one another, especially when the hip is bent. 

Two parts, of the hip include:  

  • The ball — called the femoral head — which is at the upper end of your femur (thigh bone).
  • The socket — called the acetabulum — which is part of your pelvic bone.

The two types of cartilage are:

  • Articular cartilage covers the ball and socket and allows the hip joint to move smoothly.
  • The labrum is an "O ring" of soft tissue that goes around the socket forms a tight seal around the hip to stabilize the hip joint.

FAI leads to the ball and socket impacting one another. 

FAI can cause hip pain, especially when the hip is brought toward the chest during sports or sitting for long periods. Over time, this can damage the cartilage that cushions the hip.

It's thought that about 15% of people with hip pain have FAI. Some people don't have symptoms and it often goes undiagnosed.

There's no clear data on how many people have FAI.

Types of FAI

There are three types of FAI:

  • Pincer impingement happens because extra bone extends out over the normal rim of the hip socket which can wear away the cartilage.
  • Cam impingement happens when extra bone grows on the ball of the hip joint. Since the ball of the hip is no longer round, it can't rotate smoothly and can hit against the socket.
  • Combined/mixed impingement means that both the pincer and cam types are present.

Femoroacetabular impingement causes

Hip deformities at birth or bone growth during childhood can cause FAI.

It affects both males and females.

Over time, and with repeated motion, bone deformities may start to damage the cartilage and cause pain.

It's not clear what triggers the changes, in the shape of the ball or socket, but the following may play a role:

  • Genes or family history.
  • The way the spine and pelvis align.
  • The range of motion of the hips.

FAI is most common in teens, young active adults, and athletes.

Physical activity doesn't cause FAI. Rather, active people are more likely to notice hip pain sooner than others.

FAI complications

If left untreated, symptoms often get worse.

Over time, FAI can lead to osteoarthritis (the breakdown of cartilage around the hip joint), or joint deterioration. This can be painful and limit the ability to be active.

If you're noticing persistent pain in your hip joint, you may have some damage to the cartilage. It's important to inform your doctor for evaluation and possible treatment to keep your hip healthy.

How to prevent FAI

Most of the time, you can't prevent FAI.

You can adapt your activities and keep the hip and abdominal muscles strong to help slow the damage to your cartilage.

Why choose UPMC Orthopaedic Care for FAI?

U.S. News and World Report ranks us as one of the best orthopaedic programs in the nation.

Here are just a few of the reasons why:

  • Experts in sports medicine. As experts in preventing and treating sports-related injuries, we know the problems athletes face. We know you want to stay active and keep playing the sport you love. We use the most advanced treatments and therapies to make that happen.
  • Interconnected services. We offer one place for all your orthopaedic needs. Our doctors, nurses, and physical therapists provide complete care — from diagnosis through recovery and rehab. We coordinate all of your care, so all you have to focus on is getting better.
  • Many ways to rehab. We have more than 70 locations throughout the region where you can go for outpatient rehab.
  • Unmatched in research. We are leaders in the western Pa. region for NIH-funded orthopaedic research and clinical trials. We're always seeking better ways to diagnose and treat conditions such as FAI.
  • Specialty programs. With specialists in each type of orthopaedic injury and condition, we have the experts to cater to your specific needs. The Hip Preservation Program at UPMC Orthopaedic Care specializes in hip problems from the mild to the severe, including FAI.

Femoroacetabular Impingement Symptoms and Diagnosis

Many people don't have any symptoms of FAI, but others may notice:

  • Hip pain that gets worse with physical activity or after long periods of sitting.
  • Catching or locking in the groin area.
  • Groin pain that wraps around the back of your hip.
  • Stiffness or less range of motion in your hip(s).
  • Popping or clicking
  • Limping.

If you have mild pain, you can try:

  • Changing your workouts, especially if there are certain activities that trigger discomfort.
  • Resting your hip.
  • Taking ibuprofen or an NSAID pain reliever.

If the pain doesn't go away, or it gets worse, you should call your doctor.

Diagnosing FAI

During your appointment, your doctor will:

  • Ask about your health history and symptoms.
  • Look at your posture.
  • Watch how you walk.

The doctor will also perform range of motion, strength, and impingement tests to check how your joint moves and whether it causes pain.

During an impingement test, doctors:

  • Bring your knee up toward your chest.
  • Rotate it toward your opposite shoulder.

If you have pain during the test, you may have FAI.

Your doctor may also do other tests to diagnose FAI, such as:

  • X-rays to view your bones.
  • MRI to see if you have cartilage damage.
  • CT scan to see the exact shape of your hip.
  • A numbing shot to the joint. If the numbing medication relieves your pain, it can help diagnose FAI.

Femoroacetabular Impingement Treatment

Treatments for FAI will vary based on how severe your pain is, and whether there is damage to your cartilage.

UPMC's orthopaedic team will work with you to reduce your pain, restore motion to the hip, and stop FAI from getting worse.

If you have FAI but don't have symptoms, treatment is not needed. You should learn more about FAI, so you know ways to reduce joint strain and when to seek treatment.

Non-surgical treatments for FAI

If you have FAI symptoms, the following treatments might help:

  • Rest.
  • Adjusting activities to put less stress on the joint.
  • NSAID pain relievers.
  • Physical therapy.

If non-surgical treatments don't help, or if tests show you have joint damage, you may need FAI surgery.

Surgery to treat FAI

FAI surgery is often minimally invasive where your surgeon:

  • Makes tiny incisions on the hip.
  • Uses a small camera — called an arthroscope — to look inside your hip joint.
  • May repair the cartilage and/or clean up damage and shave off excess bone on the ball and/or socket.

Arthroscopic surgery usually takes 1.5 to 2 hours and requires general anesthesia.

Though you'll spend some time in the recovery room, most people go home the same day.

You'll need to use crutches for at least one week after your surgery.

If arthroscopic FAI surgery isn't an option, you may need an open surgery. This is a longer procedure, with several days of recovery in the hospital.

As with all surgeries, there are rare but more serious risks such as:

  • A reaction to the anesthesia.
  • Infection.
  • Injury to the cartilage or bone.
  • Incomplete pain relief.
  • Nerve irritation.

After either type of surgery, you'll do physical therapy. It will take at least 3 to 4 months to fully heal and return to your normal routine.


FAI surgery usually relieves pain and prevents further damage to your hip joint and cartilage. However, some damage cannot be repaired and further damage may still happen in the future.

In some cases, if FAI has caused severe joint damage and you don't improve significantly after arthroscopic surgery, you may think about a hip replacement.