Femoroacetabular Impingement (FAI)

Femoroacetabular impingement (FAI) is a condition in which the bones that form the hip joint do not fit together perfectly, so they make abnormal contact and rub against each other during movement. The most typical complaint is pain felt in the groin that worsens with squatting, twisting, or prolonged sitting. For most people the first line of treatment is not surgery: with activity modification and targeted physiotherapy, many patients experience a meaningful reduction in pain and an improvement in function. ^[1][4]

What is femoroacetabular impingement (FAI)?

The hip is a ball-and-socket joint. The socket is formed by the acetabulum, which is part of the large pelvis bone; the ball is the femoral head, the upper end of the thighbone (femur). According to OrthoInfo, in a healthy hip the femoral head fits perfectly into the acetabulum, and a layer of articular cartilage covering the joint surfaces provides a smooth, low-friction surface for movement. A strong ring of fibrocartilage called the labrum surrounds the socket and acts like a gasket, providing a tight seal and adding stability to the joint. ^[1]

In FAI this fit is disrupted. There are extra bony prominences (bumps) on the femoral head, the acetabular rim, or both. This extra bone causes abnormal contact between the hip bones and prevents the joint from rotating smoothly during activity. Over time this repetitive contact can tear the labrum and wear down the articular cartilage (osteoarthritis). StatPearls describes it as "a pathologic mechanical process in which morphologic abnormalities of the acetabulum and/or femur combined with vigorous hip motion lead to repetitive collisions that damage the soft-tissue structures within the joint." ^[1][3]

An important point is that an abnormal bone shape does not always mean pain. Some people live long, active lives with FAI morphology (bone shape) and never have problems. When pain does develop, it usually signals that damage to the cartilage or labrum has begun. For this reason clinicians increasingly use the term "FAI syndrome": this refers not merely to a different bone shape on imaging, but to the situation where symptoms, clinical findings, and imaging all line up. ^[1][3]

Types of FAI

OrthoInfo and Cleveland Clinic classify hip impingement into three types:

• ·Cam type: The femoral head is not perfectly round; a bump forms at the femoral head-neck junction. Because it cannot rotate smoothly inside the socket, this bump grinds the cartilage inside the acetabulum. Cam morphology is more common in men.
• ·Pincer type: There is extra bone extending out over the normal rim of the acetabulum (the socket). The labrum can be crushed beneath this prominent rim. Pincer morphology is more common in women.
• ·Combined type: Both cam and pincer types are present at the same time, which is quite common in practice.

This distinction is not merely academic; the mechanism by which the impingement occurs influences which movements trigger pain and where rehabilitation should focus. ^[1][2]

What are the symptoms?

According to OrthoInfo, the most common symptoms of FAI are pain, stiffness, and limping. Pain often occurs in the groin area, although it may also occur toward the outside of the hip. Turning, twisting, and squatting may cause a sharp, stabbing pain, while at other times the pain is just a dull ache. ^[1]

Cleveland Clinic notes that FAI pain typically feels like a constant, dull ache in the hip that may spread to the groin, the buttock, and the thighs. Many people describe it as feeling like there is a bruise deep inside the body that someone is constantly pressing on. The pain usually gets worse during physical activity, especially with:

• ·Squatting
• ·Lunging
• ·Jumping
• ·Sitting still for a long time or driving
• ·Lying on the affected side

These activities and positions can make the pain feel sharp or stabbing. In addition, catching, clicking, the hip giving way, stiffness, and reduced range of motion are among the reported complaints. ^[1][2][5]

It is common for symptoms to begin insidiously. A person may at first feel discomfort only after a long game or an intense training session; over time this sensation appears more frequently and earlier. For this reason, recurrent, mechanical groin pain, particularly in young and active people, should not be dismissed.

What causes it and what are the risk factors?

According to OrthoInfo, FAI develops because the hip bones do not form normally during the childhood growing years. It is the deformity of a cam bone spur, a pincer bone spur, or both, that leads to joint damage and pain. When the hip bones are shaped abnormally, there is little that can be done to prevent FAI. Cleveland Clinic adds that most people are born with the unusually shaped joint, while bone spurs can also develop throughout life. ^[1][2]

A critical point to understand is this: exercise does not cause FAI. However, because athletic people work the hip joint more vigorously, they may begin to feel symptoms at an earlier age. Playing sports does not create the impingement; it can only speed up the point at which an existing bone shape begins to produce symptoms. ^[1][2]

Notable risk factors include:

• ·Age: FAI syndrome is an increasingly recognized source of hip pain in young adults. Yale Medicine notes that hip and groin pain is especially common between the ages of 20 and 45. ^[6]
• ·Sex and morphology: Cam type is more common in men, while pincer and combined types are more common in women. ^[2]
• ·History of high-intensity sport: Intense participation in sports involving jumping and rapid changes of direction—such as soccer, ice hockey, and basketball—during the adolescent years when the skeleton is still developing has been associated with the development of cam-type bone shape.
• ·Familial predisposition: A family history of similar hip morphology may increase risk.

FAI is regarded as one of the important causes of hip osteoarthritis in young adults, because repetitive abnormal contact can accelerate cartilage wear over time. ^[3][5]

How is it diagnosed?

Diagnosis is made by evaluating the history, physical examination, and imaging together. The clinician first asks about your general health and your hip complaints; learning when the pain started and which movements or positions improve or worsen the symptoms is valuable for diagnosis. ^[1][2]

The impingement test — FADIR

The best-known part of the physical examination is the impingement test. OrthoInfo describes it this way: the clinician brings your knee up toward your chest and then rotates it inward, toward the opposite shoulder. If this re-creates your hip pain, the test is considered positive for impingement. In the literature this maneuver is known as the FADIR test (Flexion-Adduction-Internal Rotation). The FADIR test has very high sensitivity (its ability to catch the condition); that is, if the test is negative, FAI becomes less likely. By contrast, its specificity is low, so a positive result does not confirm the diagnosis on its own, because other hip problems can also make the test positive. For this reason the test must be interpreted together with the history and imaging. ^[1][5]

Imaging tests

According to Cleveland Clinic and OrthoInfo, the following imaging may be used to clarify the diagnosis:

• ·X-ray: Provides good images of bone and shows the abnormal bone shapes seen in FAI; it can also show signs of arthritis.
• ·Computed tomography (CT): More detailed than a plain X-ray; shows the exact abnormal shape of the hip.
• ·Magnetic resonance imaging (MRI): Shows soft tissue much better; helps identify damage to the labrum and articular cartilage. Injecting contrast dye into the joint (MR arthrography) can make the damage show up more clearly.
• ·Diagnostic local anesthetic injection: The clinician may inject a numbing medicine into the joint; if the pain is temporarily relieved, this supports the hip joint as the source of the problem.

Because FAI morphology is a frequent finding on imaging, a diagnosis is not made simply because the bone shape looks different on a scan; the clinical picture must also match. ^[1][2]

Treatment options

Treatment of FAI progresses from non-surgical (conservative) methods to surgery when necessary. As OrthoInfo and Cleveland Clinic emphasize, the first step is generally not surgery. ^[1][2]

Non-surgical (conservative) treatment:

• ·Activity modification: The clinician may first recommend changing your daily routine and avoiding movements that trigger symptoms (for example, deep squats). The goal is to stay active while temporarily steering clear of impingement positions.
• ·Medications for pain and inflammation: Nonsteroidal anti-inflammatory drugs (NSAIDs) can help reduce pain and inflammation. Cleveland Clinic notes that in resistant cases a corticosteroid injection into the joint may be considered at the clinician's discretion. (Decisions about medications and dosing are made only by your doctor.)
• ·Physiotherapy: Targeted exercises that improve hip range of motion and strengthen the muscles that support the joint can relieve stress on the injured labrum or cartilage. This is at the center of conservative care.

Surgical treatment: If imaging shows joint damage caused by FAI and the pain is not relieved by non-surgical treatment, the clinician may recommend surgery. Many FAI problems can be treated with hip arthroscopy, performed through small incisions with thin instruments; using a camera (arthroscope) placed inside the joint, the surgeon repairs or cleans out the damage to the labrum and cartilage and corrects the impingement by trimming the extra bone on the acetabular rim and shaving down the bump on the femoral head. Some severe cases may require open surgery with a larger incision. OrthoInfo notes that surgery can correct the impingement and prevent future joint damage, but that if treatment has been delayed, existing damage may not be completely repaired. ^[1][2]

Which path is chosen is personalized according to the severity of symptoms, the degree of joint damage, and the person's age, activity level, and goals. One-size-fits-all advice from the internet is not right for everyone.

How can physiotherapy help?

Physiotherapy is a cornerstone of the non-surgical management of FAI syndrome. The Personalised Hip Therapy (PHT) protocol developed in the NHS-supported FASHIoN trial is built on four core components delivered by physiotherapists: a detailed patient assessment; education and advice; help with pain relief; and an individualized, supervised, progressively advanced exercise-based program. This program is typically delivered over 12-26 weeks. ^[4]

The main areas physiotherapy targets in FAI include:

• ·Improving movement quality: Relearning squatting, bending, and sitting mechanics in ways that reduce the positions that trigger impingement.
• ·Strength around the hip: Strengthening the hip abductor and external rotator muscles in particular can improve control of the femoral head within the socket and balance the load on the joint.
• ·Core (trunk) stability: Developing lumbopelvic control helps reduce the stress placed on the hip.
• ·Flexibility and soft tissue: Releasing tight or restricted structures with controlled stretching and manual techniques.
• ·Motor control and balance: Restoring proprioception (the sense of joint position) and a graded return to daily and sporting movements.

Scientific reviews report that in the short term, conservative interventions are effective in reducing pain and improving function in FAI, and that physiotherapy can produce meaningful improvements in both pain and function. Exercises are usually learned first under the guidance of an experienced physiotherapist and can then be continued either in a rehabilitation center or at home. ^[4][5]

At FizyoArt, we help you continue this process in your own home. With our home-based orthopedic rehabilitation services in Istanbul, Ankara, and Antalya, you can carry out an individualized exercise program in your own environment; with home manual therapy in Izmir, you can support soft-tissue and joint-mobility work. The content of the program is always determined according to your assessment findings and your doctor's recommendations.

What can be done at home; who is it suitable for, and who is it not

OrthoInfo notes that when symptoms first occur, it can be helpful to try to identify an activity that may have caused the pain, modify your activities accordingly, rest the hip, and see whether the pain settles. Over-the-counter anti-inflammatory medicines (such as ibuprofen and naproxen) may help relieve pain; however, you should check with your doctor about whether they are appropriate for your own health situation. ^[1]

Things that can usually be done safely at home include:

• ·Temporarily limiting movements that trigger impingement (deep squats, prolonged cross-legged sitting, excessive hip flexion).
• ·Breaking up long periods of sitting; adjusting seat height and time spent seated.
• ·Consistently continuing the pain-free strength and mobility exercises taught by your physiotherapist.
• ·Keeping a pain diary to notice which activities worsen symptoms.

Who is a home program suitable for? A home program is generally suitable for people whose symptoms are mild to moderate, who have no red flags, and who have been assessed and guided by a doctor or physiotherapist. Conservative treatment is a reasonable, evidence-based first step for most patients. ^[4]

Who is it not suitable for, or who needs assessment first? It is not appropriate for people who have never been evaluated and whose diagnosis is not yet clear to start an exercise program on their own, because groin pain can have many other causes. In people with progressively worsening pain, significant locking or catching in the hip, advanced joint damage, or pain that seriously limits daily life, the program must be individualized under professional supervision. Trying to "stretch through" pain or doing aggressive exercises from generic internet videos can make damage worse.

When should you see a doctor?

OrthoInfo emphasizes that if symptoms persist, you should see a doctor to determine the exact cause of the pain and to review treatment options, and that the longer painful symptoms go untreated, the more damage FAI can cause in the hip. Cleveland Clinic recommends seeing a doctor for FAI symptoms that last more than a few weeks, for complaints that make it hard to move, or when treatments such as NSAIDs or physiotherapy that previously worked are no longer effective. ^[1][2]

Seek medical care without delay in the following situations (red flags):

• ·Hip or groin pain that does not improve within a week or two and is getting worse
• ·A clear sense of locking, catching, or the hip giving way
• ·Pain that seriously limits walking, climbing stairs, or using the hip
• ·Treatments that previously helped now losing their effect

Symptoms such as an inability to move the hip at all after significant trauma, numbness or weakness in the leg, fever, or unexplained weight loss may point to different, urgent conditions; in these situations, seek emergency medical evaluation without losing time.

Early evaluation offers the chance of a less invasive treatment option and a more controlled recovery.

Short summary (TL;DR)

• ·What it is: FAI is abnormal friction and pain during movement caused by the abnormal shape of the bones forming the hip joint. It has three types: cam, pincer, and combined. ^[1]
• ·Symptoms: Mostly groin pain, stiffness, and limping; worsened by squatting, twisting, prolonged sitting, and lying on the side; catching or locking may occur. ^[1][2]
• ·Causes: Usually the bones not developing normally during childhood growth. Exercise does not cause FAI but can make symptoms appear earlier. ^[1]
• ·Diagnosis: History + FADIR (impingement) test + X-ray/CT/MRI. A positive test alone does not establish the diagnosis. ^[1][5]
• ·Treatment: Conservative first (activity modification, medication for pain control, physiotherapy); hip arthroscopy when needed. ^[1][2]
• ·Physiotherapy: Individualized, supervised exercise programs lasting 12-26 weeks can reduce pain and improve function. ^[4]
• ·When to see a doctor: Pain that does not improve in a few weeks and is worsening; locking; treatments losing their effect. ^[2]

Frequently Asked Questions

Will femoroacetabular impingement (FAI) go away on its own?

The underlying bone shape in FAI does not change on its own. However, according to Cleveland Clinic, most people can manage their symptoms with non-surgical methods. In other words, even though the bone shape remains, pain and function can improve significantly with appropriate activity modification and physiotherapy. ^[2]

Does exercise or sport cause FAI?

No. OrthoInfo states clearly that exercise does not cause FAI. FAI develops when the bones form abnormally during the growth period. Athletic people may simply feel symptoms earlier because they use the hip more intensively. ^[1]

Is there a link between FAI and osteoarthritis?

Yes. Repetitive abnormal contact can lead to a labral tear and cartilage wear over time. FAI is regarded as one of the important causes of hip osteoarthritis in young adults. For this reason, leaving symptoms untreated for a long time is not recommended. ^[1][3][5]

Does physiotherapy replace surgery?

For many patients, conservative treatment and physiotherapy are the first step and can control symptoms without the need for surgery. However, if imaging shows significant joint damage and the pain is not relieved by non-surgical treatment, surgery may be considered. The decision is personalized according to the clinical picture and your doctor's evaluation. ^[1][2][4]

Which exercises can I do at home?

Home exercises focus on strength around the hip, core stability, flexibility, and movement control. However, these exercises must first be determined by a physiotherapist according to your assessment findings. Generic, unsupervised exercises that trigger pain can make damage worse. ^[4]

Is FAI pain always felt in the groin?

It is most often felt in the groin, but the pain can also spread to the outside of the hip, the buttock, or the thigh. Some people describe a dull ache, while others describe a sharp, stabbing pain with movement. ^[1][2]

Can I return to sport after hip arthroscopy?

Cleveland Clinic notes that FAI surgery has a high success rate and that many people are able to stay active and continue playing sports. You may need to modify certain movements. The timing of return to sport is determined according to the guidance of your surgical team and your physiotherapist. ^[2]

Is FAI the only cause of groin pain in young adults?

No. Groin and hip pain can have many causes, including muscle strain, inguinal hernia, and bursitis. For this reason, rather than self-diagnosing, it is important to be evaluated by a doctor for recurrent, mechanical hip or groin pain. ^[1][6]