Hip Impingement

What is hip impingement?

Hip impingement is a common cause of hip pain among young athletes and physically active adults.

The condition, also known as femoroacetabular impingement (FAI), occurs when one or both of the bones in the hip joint develop abnormally. In a healthy hip, the top of the thigh bone (femoral head) moves freely inside the hip socket (acetabulum). But if one or both bones is misshapen or has excess bone growth on its surface, the bones rub together and cause friction.

Hip impingement typically becomes painful when the friction between bones damages the labrum, the soft tissue that cushions the hip joint. This is called a labral tear. Hip impingement can also damage the cartilage layer in the joint, which eventually leads to osteoarthritis.

Sitting for prolonged periods can cause hip impingement to become painful, as can certain sports. Hockey, gymnastics, rugby, and other sports with a lot of twisting, turning, and squatting can cause hip impingement to progress. Over time, the athlete may find training and competing increasingly painful.

Hip impingement: Here is a look at a healthy hip, a hip with a cam impingement, and a hip with a pincer impingement.

There are three types of hip impingement:

  • Cam impingement occurs when the thigh bone is not perfectly round and rubs against the hip socket during certain types of motion.
  • Pincer impingement occurs when the hip socket (acetabulum) bone is too deep and rubs against the thigh bone (femur).
  • Combined impingement refers to abnormal development or growth on both the femur and the acetabulum.

What are the symptoms of hip impingement?

Some people with a hip shape that may cause impingement may never experience pain or other symptoms. Others, especially people who are active, develop symptoms as early as their teens. If and when symptoms appear, they are usually a sign that the labrum or cartilage has been damaged.

If your child has symptomatic hip impingement, early diagnosis will give them the best chance of a successful recovery and full return to activities, including sports.

Signs and symptoms of hip impingement can include:

  • pain in the groin or hip
  • pain from activity (such as sports or dancing) or prolonged sitting
  • difficulty flexing the hip
  • limping
  • popping or clicking of the hip
  • stiffness in the groin or front of the thigh

What causes hip impingement?

No one knows what causes an abnormal bone shape that may lead to hip impingement. The abnormal bone shape that may cause impingement likely develops as a child’s hip joints develop over time. Doctors and researchers don’t know what causes this to happen. 

Sometimes, hip impingement is caused by other hip conditions, such as slipped capital femoral epiphysis (SCFE) and Legg-Calve-Perthes disease.

Although physically active people often develop symptoms sooner than less active people, exercise does not cause hip impingement.

Meet Louise

Hip impingement and dysplasia forced the track star to give up running. Her surgeon printed a 3-D model of her hip joints to better understand and correct the irregularities causing her pain.


How we care for hip impingement

The Child and Young Adult Hip Preservation Program at Boston Children’s Hospital provides world-class care for patients of all ages. We tailor our care to the needs of teens, starting with a thorough exam. We use MRI techniques developed jointly with the Department of Radiology to diagnose the condition and reduce our patients’ future risk of osteoarthritis. Whenever possible, we take a non-surgical approach to treatment. However, if surgery is called for, our surgeons are pioneers in minimally invasive arthroscopic surgery.

Patient resources

Download our hip impingement fact sheet to learn more about the condition, how it occurs, and how the specialists in our Child and Young Adult Hip Preservation Program approach care.