Abnormal Bone Growth That Causes Friction Within the Hip Joint

Femoroacetabular impingement (FAI) is a condition affecting the femur (thighbone) and acetabulum (hip socket). The top of the femur (femoral head) fits into the acetabulum, forming the ball-and-socket hip joint. FAI occurs when either an abnormal growth on the femoral head or overhanging of the acetabulum causes the two bones to rub against each other in a way that causes pain.

There are two types of FAI: 

  • Cam impingement. In this type, there is a bony deformity on the femoral head that causes it to no longer be round and smooth. Cam impingement is more common in men. 
  • Pincer impingement. With pincer impingement, the acetabulum is not positioned correctly or covers too much of the femoral head.

Though the cause of FAI is not known yet, athletes and younger, active adults are most at risk for the condition. Sports and activities often associated with FAI include soccer, football, baseball, ice hockey, golf, lacrosse, cycling, rowing, deep squatting and ballet.

Symptoms, Diagnosis and Outlook

Femoroacetabular impingement causes pain in the hip or groin, especially when you raise your leg or turn your foot in toward your body. Limitations in range of motion of the hip joint are also a sign of FAI.

Your doctor can diagnose FAI by completing a physical exam and reviewing your medical history. An X-ray scan or a special type of MRI test called an MR arthrogram may also be done to further assess the affected hip.

FAI that is causing pain may be best treated with surgery. Many active adults experience pain relief after surgery. If left untreated, FAI can lead to hip arthritis.

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Penn State Health includes the Milton S. Hershey Medical Center. Hershey Medical Center is ranked as one of the best orthopedic providers in the country by U.S. News & World Report. This honor was earned because our doctors consistently deliver exceptional patient care and outcomes through their commitment to advanced treatments, translational research and provider training.

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As part of Penn State Bone and Joint Institute, our Healthy Hip Program offers state-of-the-art, comprehensive care for hip pain. Here, you have a dedicated team of orthopedic and sports medicine experts with separate hip training working to provide you with individualized care. Subspecialty providers from sports medicine, orthopedic trauma, pediatric orthopedics and radiology support the program, helping to ensure the most accurate diagnoses and best patient outcomes.

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Penn State Bone and Joint Institute is a Blue Distinction Center for Knee and Hip Replacement. This superior designation from BlueCross BlueShield is only given to health care facilities and providers that stand out for their expertise in delivering specialty knee and hip replacement care. Our surgeons perform more than 1,000 joint replacement procedures every year.

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We developed a join replacement education website just for patients undergoing joint arthroplasty. The website takes you step by step through the joint replacement process. From things to consider before choosing surgery to recovery after surgery, you’ll find the information you need to help you feel confident in your decision to undergo joint replacement.

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The doctors and researchers in our Center for Orthopaedic Research and Translational Science at the Milton S. Hershey Medical Center are committed to advancing our field through scientific discovery and education. As the only academic medical center in central Pennsylvania, Hershey Medical Center is a national leader in research, in partnership with Penn State College of Medicine, and on the leading edge of new treatment options, including clinical trials.

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