Femoroacetabular Impingement (FAI)

The hip is one of the largest joints in the human body and is a ball-and-socket joint. The ball is the femoral head, which is the upper end of the femur (thighbone). The socket is formed by the acetabulum, which is part of the large pelvis bone. The bone surfaces of the ball and socket are covered with articular cartilage, a smooth, white connective tissue that enables the bones of a joint to easily glide over one another with very little friction allowing easy movement. Large ligaments (tough bands of tissues) connect the ball and the socket in order to stabilize the joint by preventing excessive movement. The acetabular labrum is a ring consisting of fibrous cartilage and dense connective tissues surround the femoral head. The acetabular labrum acts like a gasket or seal to help hold the femoral ball at the top of the thighbone securely with the acetabulum socket.


Femoroacetabular impingement (FAI), also known as hip impingement, is a mechanical condition or structural disorder where the bones of the hip are abnormally shaped. Since they do not fit together perfectly, over time, the hip bones repetitively "bump" or rub against each other and cause damage to the joint, cartilage or the labrum. Femoroacetabular impingement occurs when the femoral head (ball) does not have its full range of motion within the acetabulum (socket). Femoroacetabular impingement can occur in people of all ages, including adolescents and young adults.

There are three main types of femoroacetabular impingements:

Cam Impingement - In cam impingement, the femoral head is not perfectly round, therefore it cannot rotate smoothly within the acetabulum. This is due to excess bone that has formed around the femoral head (bone spur). The bone spur grinds the cartilage inside the acetabulum.

Pincer Impingement - In pincer impingement, extra bone extends out over the normal rim of the acetabulum, crushing the labrum. When the hip is flexed, the neck of the femur bumps against the rim of the socket, resulting in damage to the cartilage and the labrum.

Combined Impingement - In combined impingement, both cam and pincer impingement occur together.


In the early stages of hip impingement, there may be mild or no associated symptoms. Individuals who are experiencing femoroacetabular impingement may have the following symptoms:

  • Pain in the groin area especially after hip flexion
  • Pain in the groin, hip, or lower back during rest and/or activity
  • Stiffness in the groin, hip, or thigh
  • Inability or difficulty flexing the hip beyond a right angle

If symptoms worsen or do not improve with more-conservative treatment such as medication, rest, and physical therapy, it is highly recommended to visit a physician to rule out any other causes and avoid further damage. An early and accurate diagnosis of femoroacetabular impingement is crucial since an untreated hip impingement can lead to significant cartilage damage and osteoarthritis.


Femoroacetabular impingement can be diagnosed with a combination of physical examination and imaging studies. After gathering information about the individual's general health and the extent of his or her hip pain and how it affects their ability to perform day-to-day activities, the physician may conduct the impingement test where the knee is brought up towards the chest and rotated inward towards the opposite shoulder to see if this recreates the hip pain. The physician may order X-rays to check for structural abnormalities in the hip joint, a CT scan to see the exact shape of the hip bones, or an MRI scan to determine the condition of the tissues and bones of the hip. A colored, fluid dye may be injected into the joint space prior to your MRI scan to better define the damage. After a thorough analysis, the physician will recommend the appropriate course of treatment.


Treatment of femoroacetabular impingement will heavily depend on the severity of the individual's conditions. Often, symptoms subside with more-conservative non-operative treatments. However, if that fails, the physician may recommend an arthroscopic hip surgery to remove or repair the torn portions of the labrum.

Rest - It is advised to decrease or completely stop the activity that makes the pain worse. A great way to stay active while allowing the symptoms to subside is to switch to low-impact, cross-training activities such as biking or swimming.

Medication - Over-the-counter medication such as ibuprofen and naproxen usually help reduce pain and swelling. If these are deemed insufficient by your physician, they might prescribe stronger medication to relive pain and reduce inflammation.

Physical Therapy - Physical Therapists will often prescribe specific strengthening and stretching exercises that promote healing and strengthening of the hip joints.

Surgery - If symptoms persist after all non-operative treatments are exhausted, an arthroscopic surgery may be deemed necessary. During the procedure, an arthroscope, which is a small, flexible tube with a camera attached, is inserted into the hip joint. Two or three small incisions, called portals, are made to allow the scope and other surgical instruments to enter through a narrow space between the femoral head (ball) and the acetabulum (socket). Once inside, the physicians will examine the femoral head and acetabulum for any bone overgrowth and either trim or shave the spurs. The physician will also examine the labrum and the articular cartilage surrounding the hip joint to identify any inflammation, loose bodies, etc. and make any necessary repairs removing loose fragments of cartilage or trimming torn portions of the labrum. Once all the repairs are made, the incisions are closed with sutures, steri-strips, or small bandages and the procedure will be completed. In very few cases, people with femoroacetabular impingement may require a total hip replacement depending on the extent of damage and arthritis affecting the hip joint.


Recovery with more-conservative treatment will vary based on the extent of the damage and the severity of the individual's symptoms. Hip arthroscopy often results in a quick recovery process as symptoms often improve immediately following the procedure. Swelling generally subsides within a week and the sutures will either dissolve or be removed in seven to ten days. The time of recovery will depend on the severity of the labral tear. Regardless, a physical therapist will provide instructions on the specific exercises to strengthen the leg and restore hip movement to allow for walking and other activities post operatively. Each patient is unique, so the recovery period will vary depending on the level of activity the individual hopes to return to; this should be discussed with the physician as well as the physical therapist.



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