Femoroacetabular Impingement (FAI)

Femoroacetabular impingement, or FAI, is a condition where the bones of the hip are abnormally shaped. Because they do not fit together perfectly, the hip bones rub against each other and cause damage to the joint. The damage can occur to the articular cartilage (the smooth white surface of the ball or socket) and/or the labral cartilage (the soft tissue of the socket). (FAI is also referred to as femoral acetabular impingement and femoral-acetabular impingement.)

FAI can lead to pain, labral tears and decreased range of motion. 

There are several types of femoroacetabular impingement, and the University of Michigan Health System treats them all:

  • Cam impingement - Because the head and the neck are not perfectly aligned, motions such as deep flexion and internal rotation can erode cartilage from the ends of the bone or tear the labrum. This can result in pain and wear of the hip joint. It is called cam impingement because the femoral head and neck has a bony bump that projects out like the cam used in rotating machinery.
  • Pincer impingement  - Pincer impingement is characterized by overhanging bone on the edge of the acetabulum. This type of impingement got its name from the pinching (pincer) of the labrum between the femoral neck and head and the excess bone of the acetabulum. This can result in labral tears and eventually lead to pain and wear of the hip joint.
  • Combined - Patients can have both cam and pincer impingement at the same time. 

Our experts at the University of Michigan Department of Orthopaedic Surgery are extremely knowledgeable in treating femoroacetabular impingement. As one of the oldest and most well-regarded orthopaedic units in the country, we have successfully diagnosed and treated hundreds of patients with FAI and can offer you a wide range of the latest non-surgical and surgical options for your particular condition.

As part of the U-M Comprehensive Musculoskeletal Center, we work throughout the University of Michigan Health System with every area that will be involved in the special care that is needed for bones and joints in order to develop the best treatment plan for you. 

FAI Symptoms

Typical symptoms include:

  • Deep groin pain with certain activities
  • "Catching," locking, grinding sensation in the hip or groin
  • Pain with prolonged sitting
  • Pinching type pain when flexing hip past 90 degrees
  • Occasional pain radiating to thigh, knee or buttock
  • Pain with exercise or sports

Diagnosis of FAI

At the University of Michigan, we will:

  • Take your medical history and ask you about your pattern of symptoms
  • Conduct a physical exam
  • Review any previous X-rays or additional information forwarded to us by your referring physician, if there is one

We may also order:

  • X-ray (2-dimensional view of the bone) -  This is a non-invasive tool used to evaluate the hip joint.
  • MR arthrogram - This involves an injection of a contrast material into the joint to evaluate soft tissue, cartilage defects and labral tears. This is more sensitive than a standard MRI for evaluation of labral tears.
  • CT scan – This may be ordered if surgery is being considered for your FAI.

FAI Treatment

Non-surgical Treatment for FAI 

Based upon our findings, your U-M physician may recommend:

  • Weight loss, if you're over your ideal body weight
  • Activity modification
  • Physical therapy
  • NSAIDs (non-steroidal anti-inflammatory drugs) for pain
  • Injections - These injections are used for both diagnostic and therapeutic reasons. They may be done at the time of the MR arthrogram. The typical injection is both an anesthetic and a steroid. They may provide pain relief for weeks to months. These are typically done in Radiology under fluoroscopic or ultrasound assistance.

Surgical Treatment for FAI

Whether you will need surgical treatment depends to a large degree on the type of FAI you have, the amount of deformity and the presence of arthritic change. Here are some surgical options:

  • Arthroscopy (scope) - This is performed through small incisions in the skin to allow a camera to see the structures within the hip. This can address the labrum, the femoral head deformity and/or an abnormally shaped acetabulum. This is typically performed by a U-M surgeon who specializes in sports injuries and/or has formal training in hip arthroscopy. Patients with pre-existing hip arthritis are typically NOT candidates for hip arthroscopy. The labrum can either be debrided (trimmed) or repaired. This is determined by the quality of the labrum and the size of tear along with the type of deformity.
  • Open surgical dislocation - The blood supply to the hip is preserved while dislocating the ball from the socket. The procedure allows increased exposure to correct the deformities of the ball or socket. Surgical dislocation of the hip is performed by U-M surgeons with advanced training in surgical dislocation for a variety of types of FAI with the absence of advanced arthritis.
  • Osteochondroplasty - Excess bone on the femoral neck, or acetabulum, is removed in order to re-establish a round femoral head (ball) and a normally-shaped socket. After surgery, patients may be limited on how much weight they can bear to protect from fracturing the hip. An osteochondroplasty can be performed either through an arthroscope (camera) or through open surgery.
  • Total hip replacement - Total hip replacement is performed by a University of Michigan surgeon who specializes in hip replacement. This operative procedure removes the femoral head, neck and damaged cartilage. The bone is then replaced with metal, plastic or ceramic bearing surfaces. This procedure is offered when the femoroacetabular impingement has led to extensive cartilage damage on the femoral head (ball) and the acetabulum (socket). This is an open procedure with an incision; it is not performed under arthroscopy (scope). This is the definitive treatment for FAI, labral tears and hip dysplasia (shallow socket) when arthritis has occurred. Total hip replacement can be either a first-choice procedure or a salvage procedure when a previous scope or open dislocation has failed. It has extremely durable results at and beyond 20 years and is being performed in young patients through less invasive techniques, which allow for earlier recovery.

Contact Us / Make an Appointment

  • MedSport, 877-877-9333, or 734-930-7400
  • Orthopaedics, 734-936-5780

Selecting a health care provider is a very important decision. Because we are highly experienced in successfully treating hip conditions such as FAI, we would like to help you explore your options. Visit our Contact Us page to see a list of Musculoskeletal Call Centers. Our staff will be glad to talk with you about how we can help.