Femoroacetabular Impingement (FAI)

Femoroacetabular impingement (FAI) is a common source of discomfort in the hip and groin region.

Also referred to as hip impingement, FAI occurs when the top of the upper femur (thigh bone) has an abnormal shape, leading to misalignment and friction between the bones in the hip joint. Over time, this repetitive rubbing gradually damages your hip joint.

UPMC offers a range of FAI treatment options, including nonsurgical and minimally invasive surgical approaches. Your doctor will consider your pain level and the amount of cartilage damage when recommending treatment.

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On this page

• What Is Femoralacetabular Impingement (FAI)?
• What Are the Symptoms of FAI?
• How Do You Diagnose FAI?
• How Do You Treat FAI?

What Is Femoroacetabular Impingement (FAI)?

Femoroacetabular impingement (FAI), or hip impingement, is a condition where extra bone grows on the femoral head in the hip joint. As the misshapen femoral ball repeatedly moves, it erodes the cartilage in the hip socket, leading to discomfort and pain.

You'll usually feel discomfort when you bend at the hip or sit for long periods. Prolonged repetitive motion can also damage the cartilage that cushions the hip.

The hip joint consists of:

• The femoral head. The ball at the top of the femur.
• The acetabulum. The socket in the pelvic bone.

Two types of cartilage in the hip are:

• Articular cartilage. Covers the ball and socket for smooth movement.
• The labrum. A ring of soft tissue that provides stability to the hip joint.

How common is a hip impingement?

Around 15% of people with hip pain have FAI. Although precise data on its prevalence is lacking, FAI is a common cause of hip and groin pain, especially among men and women aged 20 to 45.

Some people may not have symptoms, making diagnosing FAI challenging. However, teenagers, active adults, and athletes often discover their condition earlier because they have hip pain during their activities, leading them to seek a diagnosis sooner.

What are the types of FAI?

There are three types of FAI:

• Pincer impingement. Extra bone growth over the normal rim of the hip socket can lead to the wearing away of cartilage over time.
• Cam impingement. In this type, there's too much bone growth on the ball of the femur in the hip joint. This altered shape of the ball prevents smooth rotation and can cause it to impact against the socket.
• Combined/mixed impingement. This is when both pincer and cam impingements are present in the hip joint.

What causes FAI?

The exact causes of FAI aren't fully understood. However, factors such as hip abnormalities that you're born with, family history, and alignment issues may contribute to its development.

What Are FAI Risk Factors and Complications?

Hip impingement risk factors

The risk factors associated with FAI include:

• General risk factors, including age and gender.
• Congenital hip deformities, which are hip abnormalities you're born with.
• Irregular bone growth during childhood.
• Genetic predisposition and family history.
• Pelvic or spinal misalignment.
• Hip range of motion, either reduced or excessive.
• Lifestyle factors, such as poor nutrition, excessive alcohol consumption, drug use, and lack of exercise.

FAI complications

If left untreated, FAI symptoms often get worse. Over time, FAI can lead to osteoarthritis (the breakdown of cartilage around the hip joint) or joint deterioration.

How can I prevent FAI?

In most cases, you can't prevent FAI. But if you have persistent pain in your hip, you can prevent further damage by seeing your doctor.

You can also modify your activities and focus on strengthening your hip and abdominal muscles to reduce the potential for cartilage damage.

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What Are the Signs and Symptoms of FAI?

Symptoms of FAI occur because of damage to cartilage around the hip joint. Pain often begins in the groin area because of its location on the hip.

FAI symptoms might include:

• A feeling of instability or looseness in your hip joint.
• Difficulty or pain while sitting for extended periods.
• Difficulty with activities that require hip movement, such as walking, running, or climbing stairs.
• Hip pain that persists or worsens over time.
• Hip pain that radiates down to your thigh or knee.
• Limited range of motion in your hip joint.
• Swelling or inflammation around your hip joint.
• Weakness in your hip muscles.

When should I see a doctor about my FAI symptoms?

FAI symptoms can vary from person to person, and not everyone with FAI will have all of these symptoms. But if you're experiencing any common FAI symptoms, make an appointment with your doctor.

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How Do You Diagnose FAI?

To diagnose FAI, your doctor will ask about your medical history and do a physical exam. They'll gently raise your knee toward your chest and rotate it inward. If you have any discomfort or pain during this maneuver, it may indicate a hip impingement.

Tests to diagnose FAI

To confirm the diagnosis, your doctor may request imaging tests to assess for FAI and any potential bone abnormalities. These scans will also provide a clear view of any joint damage.

Tests may include:

• CT scan.
• MRI.
• X-ray.

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How Do You Treat FAI?

FAI treatment depends on your pain severity and the extent of cartilage damage.

If you have an FAI diagnosis but don't have symptoms, you may not need treatment. But it's still important to understand your FAI diagnosis, including ways to minimize joint stress and recognize when treatment might be needed.

Nonsurgical Treatment for FAI

When you're first diagnosed with FAI, your doctor might recommend nonsurgical treatment options before considering surgery, including:

• Rest.
• Avoiding activities that worsen your hip discomfort.
• Injections for pain relief.
• Nonsteroidal anti-inflammatory drugs (NSAIDs).
• Physical therapy.
• Exercises that target and strengthen the muscles supporting the hip joint to reduce strain on the damaged cartilage and promote healing.
• Maintaining joint flexibility to alleviate symptoms.

Surgical Treatments for FAI

Orthopaedic surgeons often use minimally invasive surgical techniques called arthroscopic surgery to treat FAI.

During the procedure, your surgeon will:

• Make tiny incisions on the hip.
• Use a small camera — called an arthroscope — to look inside your hip joint.
• Repair the cartilage, clean up the damage, and shave off the excess bone on the ball and socket.

Arthroscopic surgery usually takes about two hours and requires general anesthesia. Most people go home the same day. Following surgery, you'll use crutches for at least a week.

In some cases, arthroscopic FAI surgery isn't possible due to damage to your hip joint. In these cases, your orthopaedic surgeon may choose open surgery, which typically involves a longer hospital recovery, lasting several days.

While rare, as with any surgical procedure, there are potential risks associated with FAI surgery. These may include anesthesia reactions, infections, cartilage or bone injuries, incomplete pain relief, and nerve irritation.

How long does it take to recover from FAI surgery?

Whichever surgical approach your orthopaedic surgeon chooses, physical therapy is an important part of the healing process. It typically takes a minimum of three to four months to fully heal and resume your normal activities after FAI surgery.

How effective is treatment for FAI?

FAI surgery usually relieves pain and prevents further damage to your hip joint and cartilage. However, some damage can't 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 consider a hip replacement.

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