Femoroacetabular Impingement (FAI)
Femoroacetabular impingement, commonly called FAI or hip impingement, is a condition in which the bones of the hip joint do not fit together normally. The hip is a ball-and-socket joint. The ball is the top portion of the femur, also known as the thighbone, and the socket is part of the pelvis called the acetabulum. In a healthy hip, these structures move smoothly against one another, allowing a person to walk, run, bend, squat, and rotate the leg without pain.
With FAI, there is abnormal contact between the ball and socket during movement. Over time, repeated friction can damage the cartilage and soft tissues inside the hip joint, including the labrum, which is a ring of cartilage that helps stabilize the hip. As the condition progresses, the hip can become increasingly painful and stiff, especially during physical activity or prolonged sitting.
FAI is common in athletes and active individuals, but it can also affect people who are not highly active. Many individuals may have mild changes in the shape of the hip bones without symptoms, while others develop significant discomfort that interferes with daily life.
There are three main types of FAI. Cam impingement occurs when the ball portion of the hip is not perfectly round. Because of this abnormal shape, the ball cannot move smoothly inside the socket. Pincer impingement occurs when the socket covers too much of the ball portion of the hip, leading to pinching during movement. Some individuals have a combination of both cam and pincer impingement, which is known as mixed-type FAI.
FAI develops because of subtle abnormalities in the shape of the hip joint. In many cases, these changes develop during growth and adolescence. The exact reason why some people develop abnormal hip bone shapes is not fully understood, but genetics and activity levels during skeletal development may play a role.
Athletes who participate in sports involving repetitive hip motion, such as hockey, soccer, football, dance, martial arts, and basketball, may have a higher likelihood of developing FAI-related changes. Repetitive stress on the growing hip joint may contribute to abnormal bone formation around the hip.
Not everyone with these structural changes develops symptoms. Some people live their entire lives without knowing they have FAI. Symptoms typically occur when the abnormal bone contact begins damaging the labrum or cartilage within the hip joint.
Over time, repeated impingement can lead to inflammation, cartilage wear, labral tears, and eventually arthritis of the hip. Early recognition of the condition may help reduce long-term joint damage.
Previous hip injuries, certain childhood hip disorders, and anatomical variations can also contribute to the development of FAI. In some patients, there is no clear cause beyond the natural shape of the hip bones.
The most common symptom of FAI is pain in the front of the hip or groin area. Many people describe a deep ache or pinching sensation within the hip joint. The pain often develops gradually and may initially occur only during certain activities.
Activities that commonly trigger symptoms include sitting for long periods, squatting, twisting, pivoting, running, climbing stairs, or getting in and out of a car. Athletes may notice decreased performance, loss of flexibility, or pain during cutting and rotational movements.
Some individuals feel pain on the outside of the hip, buttock, or thigh rather than directly in the groin. The discomfort may come and go at first but often becomes more persistent over time.
Hip stiffness is another common symptom. Patients may notice reduced range of motion, especially when rotating the hip inward or bringing the knee toward the chest. Simple movements such as tying shoes or sitting cross-legged may become difficult.
Some people experience clicking, catching, locking, or popping sensations within the hip. These symptoms can occur when the labrum becomes damaged or irritated. In more advanced cases, prolonged walking or standing may become uncomfortable.
Symptoms can vary significantly from person to person. Some individuals experience mild soreness after exercise, while others develop chronic pain that limits daily activities and exercise routines.
Diagnosing FAI begins with a detailed medical history and physical examination. An OrthoIllinois orthopedist will ask about the location of the pain, activities that worsen symptoms, previous injuries, and limitations in movement or sports participation.
During the physical examination, they evaluate hip motion, strength, flexibility, and areas of tenderness. Certain movements are commonly used to reproduce the patient’s symptoms. One of the most common examination maneuvers involves flexing the hip and rotating it inward to determine whether impingement pain occurs.
Imaging studies are an important part of confirming the diagnosis. X-rays are typically the first imaging test performed because they allow physicians to evaluate the shape of the hip bones and identify cam or pincer deformities. X-rays can also reveal signs of arthritis or joint narrowing.
Magnetic resonance imaging, commonly known as MRI, may be ordered to evaluate the soft tissues within the hip. An MRI can help identify labral tears, cartilage damage, inflammation, or other injuries associated with FAI. In some cases, contrast dye is injected into the hip joint before the MRI to provide more detailed images of the labrum and cartilage.
Occasionally, CT scans may be used to provide a more detailed understanding of the hip’s bony anatomy, particularly when surgical planning is being considered.
Because hip pain can result from many different conditions, proper evaluation is important. Conditions such as muscle strains, hip arthritis, sports hernias, lower back problems, and tendon injuries can sometimes mimic the symptoms of FAI. A thorough assessment helps ensure an accurate diagnosis and appropriate treatment plan.
When you or a loved one suffers with hip pain, contact OrthoIllinois to schedule a consultation to evaluate the hip and discuss your condition. OrthoIllinois is a premier orthopedic care provider in Northern Illinois.
