Femoroacetabular impingement, more commonly called hip impingement, is a condition where the ball of your hip (femoral head) pinches the socket (acetabulum). A combination of genes and activity-related factors likely plays a role in its development.

Hip impingements are common. Experts estimate they affect 10% to 15% of adults. Despite their prevalence, the term “femoroacetabular impingement” wasn’t coined until 2003. Health professionals now know that hip impingements are one of the leading causes of early osteoarthritis.

Read on to learn more about hip impingements, including the different types, typical symptoms, and treatment options.

Experts generally define hip impingement as irregular contact between the ball and the socket of your hip joint. A structural change in either of these parts of your hip causes the condition. A combination of genes and activity-related factors likely play a role in its development.

Doctors tend to diagnose hip impingement in young, healthy people. Athletes may develop symptoms more often and younger than people in the general population due to vigorous exercise.

People of Caucasian background seem to have hip anatomy that predisposes them to hip impingements more than people of other backgrounds.

Some research suggests people who have a sibling with hip impingement have twice the risk of developing an impingement versus a person in the general population.

There are three types of hip impingements. Doctors classify them based on which structure is affected.

Pincer impingement

In a pincer impingement, an extra piece of bone extends over the edge of your hip socket. This bone can cause your femur to rub against the layer of cartilage that lines the outside of your hip socket, called your labrum. This can cause degeneration.

Pincer impingements seem to be more common in women.

In a 2015 review of studies, researchers found the prevalence of pincer impingement among 2,114 people without hip symptoms was 67%.

Cam impingement

A cam impingement develops when the head of your femur isn’t perfectly round and doesn’t move smoothly inside your hip socket. Over time, this can cause a bump to form on your femur head that grinds down your hip’s labrum.

In the same 2015 review, researchers found cam impingement in 37% of people without hip symptoms.

Incidence was higher (54.8%) in athletes without hip symptoms. A 2016 study identified soccer and martial arts as the most common activities in athletes with hip symptoms.

Combined impingement

A combined (or mixed) impingement is when you have features of both other types of impingements. Studies have reported the incidence of combined impingement to be between 13.7% and 44.5%.

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Illustrated by Jason Hoffman

Hip impingements often don’t cause any symptoms. When symptoms develop, it usually means there’s damage to the cartilage or labrum in the joint. You may experience:

  • hip pain or groin pain that worsens with physical activity or sitting, often with referred pain in the buttocks, thighs, or knees
  • stiffness
  • limping
  • clicking, catching, or locking of the joint
  • decreased range of motion, especially when:
    • bringing your knee toward your chest
    • rotating the front of your knee to the midline of your body

Over time, continuous rubbing of the cartilage in the joint can lead to a labral tear or the early development of hip osteoarthritis.

Hip impingement vs. hip flexor strain

A hip flexor strain is an injury of the muscle that pulls your thigh toward your chest. Symptoms can be similar to those of hip impingement, but the underlying cause is muscular as opposed to structural.

A trained health professional such as a physiotherapist can help you figure out which hip condition you have.

The diagnostic process starts with a doctor, physiotherapist, or other qualified professional considering your medical history and family history. They’ll also perform a physical exam.

During the physical exam, the health professional will likely perform the FADDIR test, which stands for flexion, adduction, and internal rotation. During this test:

  1. You will lie on your back. The practitioner will raise your affected leg so that your knee and hip are at 90 degrees.
  2. They will push your thigh across the midline of your body.
  3. Next they will move your foot and lower leg away from the midline of your body. Pain in the groin area is indicative of hip impingement.

A 2022 review found that the negative FADDIR test results (meaning you don’t have a hip impingement) were accurate 60% to 100% of the time.

Imaging can help a health professional confirm a diagnosis.

They’ll first obtain X-rays. These can help your doctor see the impingement. They may also help detect other hip conditions like arthritis and hip dysplasia, which is when the socket doesn’t fully cover the head of the femur.

Computed tomography (CT) scans can give your doctor a more detailed look at your hip. Magnetic resonance imaging can also identify labrum and cartilage tears.

Mild cases of hip impingement usually don’t need surgery. Conservative treatment options include:

If conservative methods fail to provide pain relief, a doctor may recommend surgery — which is usually performed with an arthroscope. During this procedure, they’ll make a small incision in your hip and use a long tube with special tools to fix the cause of your impingement.

Exercises to treat hip impingement

It’s essential to seek a proper diagnosis and treatment plan from a trained medical professional before starting an exercise routine. Many conditions can cause symptoms similar to hip impingement but may need different treatment.

Some of the types of exercises a healthcare professional may recommend are:

A 2020 review of studies found that a supervised physiotherapy routine, focused on active strengthening exercises and building core strength, can be more effective than unsupervised programs without those qualities.

Here are some frequently asked questions about hip impingements.

Can hip impingement heal on its own?

The actual impingement won’t heal on its own, but conservative treatments like activity modification might be all you need to relieve symptoms.

What activities or exercises should I avoid if I have hip impingement?

It’s a good idea to avoid activities that cause discomfort. You may find that squatting, prolonged sitting, or sudden twisting of your hip causes sharp pain.

Can back pain be a sign of hip impingement?

Hip impingement often causes pain localized to the groin. But it can also cause pain in areas like your outer hip, thigh, lower back, or buttocks.

Can hip impingement cause knee pain?

Some people with hip impingement experience referred pain in their knee. Referred pain means the pain comes from somewhere other than where you feel it.

Many people with hip impingements also have limited internal rotation, which may increase ACL injury risk. Your ACL is one of the main ligaments of your knee.

Hip impingement is when the ball and socket of your hip joint don’t fit together properly due to a structural difference. It’s a common condition prevalent among active people and athletes.

It’s important to visit a medical professional for a proper diagnosis and treatment plan. Without proper management, hip impingement can lead to degeneration of the cartilage in your hip and put you at risk of developing osteoarthritis.