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Femoroacetabular Impingement (FAI)

What is FAI?

The hip is a ball-and-socket joint lined by cartilage, and normally moves freely. Femoroacetabular impingement (FAI) is due to impingement or abnormal contact between the ball (femoral head) and socket (acetabulum). This is commonly the result of either an abnormally shaped ball (cam lesion) or socket (pincer lesion), or both (mixed cam and pincer). When the abnormally shaped ball or socket comes into contact with other structures (‘impinges’), it can result in damage to the cartilage along the rim of the socket (the labrum) or to the cartilage lining the socket (the articular cartilage). Tears of the hip ligament (known as the ligamentum teres) may also result.

  • Cam and Pincer Impingement
    Cam and Pincer Impingement
  • Mechanism of Cam impingement
    Mechanism of Cam impingement
  • Mechanism of Pincer impingement
    Mechanism of Pincer impingement


What are the Symptoms of FAI?

Most patients complain of pain in the groin, but pain may also radiate to your lower back, buttock or knees. The pain is often made worse with activity (including sports) and in positions where the ball and socket impinge, such as sitting in low chairs, getting up from chairs, climbing stairs, driving, and putting on shoes and socks.

Some patients also have mechanical symptoms of ‘clunking’ and ‘clicking’ in the hip.

Femoroacetabular Impingement (FAI)

How is FAI Diagnosed?

A well-trained doctor or other paramedical professional will suspect FAI based on your symptoms and a thorough examination of your hip. The diagnosis will often be confirmed by additional tests such as X-ray, CT scan with 3D reconstruction and MRI. Not all of these tests are required to confirm the diagnosis.

MRIs are helpful for looking at the soft tissues around the hip. Labral tears and any cartilaginous damage are visualised well; however, ligamentum teres tears are often difficult to visualise.

CT scans with 3D reconstruction allow a thorough view of the bony morphology of the ball and socket joint of your hip. This is helpful for planning the surgery.

What are the Causes of FAI?

The abnormally-shaped ball and socket develops as you grow. Recent research suggests a genetic link. It is quite common to have abnormal bony morphology of the hip joint. FAI develops only when the ball and socket impinges, causing damage to the joint. It is important to see your doctor early if you have hip or groin pain to diagnose this condition.

Other developmental conditions such as: Perthes, slipped upper femoral epiphyses, hip dysplasia, deep hip socket (protrusio) and coxa profunda can cause secondary impingement. This too can be diagnosed by your doctor.

Is FAI Dangerous?

FAI is not life-threatening, but it can severely impact your quality of life and function. It can affect anyone: elite athletes and the active individual, manual labourers and office workers. Untreated in the short term, FAI causes ongoing pain and disability. Untreated in the long term, cartilage damage becomes permanent and may ultimately result in the hip joint wearing out prematurely and developing osteoarthritis.

What is the Treatment?

Analgesics such as Paracetamol and anti-inflammatories can help relieve symptoms. Avoidance of the ‘impingement position’ is encouraged. Injections into the hip joint can help relieve severe symptoms temporarily. Unfortunately however, none of these modalities treat the underlying cause. Femoroacetabular impingement (FAI) is best treated with hip arthroscopy (or key-hole surgery).

All aspects of FAI can be treated successfully via hip arthroscopy:

  • Abnormal ball (cam lesion): The abnormal bone is removed and reshaped to prevent further impingement and to protect the hip from further damage. This also improves your range of motion.
  • Abnormal socket (pincer lesion): The abnormal bone is removed to prevent further impingement and to protect the hip from further damage.
  • Labral tears: These can be repaired and stabilised. Specialised anchors are used to re-attach the torn labrum.
  • Articular cartilage damage: If caught early, articular cartilage damage can be repaired and stabilised. Otherwise, unstable flaps can be removed and the underlying bone prepared to encourage new cartilage to form, a process known as micro-fracture.
  • Ligament teres tears: These can be trimmed, tightened and stabilised. Any inflamed tissue is removed.
  • Bone cysts: These can be removed or filled with a bone graft.

Participating and completing a tailored exercise program before (i.e., pre-hab) and after surgery (i.e., rehab) with a trained physiotherapist will achieve the best result for you after surgery.


When can I walk after femoroacetabular impingement (FAI) surgery?

Full weight-bearing and walking is allowed immediately. Initially, this will be aided by crutches. Most people will walk independently by 10-14 days postoperatively.

When can I drive after femoroacetabular impingement (FAI) surgery?

You should not drive for 48 hours after an anaesthetic. After 48 hours, your ability to drive will depend on the side you had your operation, left or right, and the type of vehicle you drive, manual or automatic. If you had a left hip procedure and drive an automatic, you can drive whenever you feel comfortable. Otherwise, it is reasonable to drive when you are confident with walking and can fully weight-bear on your affected side.

When can I work after femoroacetabular impingement (FAI) surgery?

Your return to work will vary depending on the procedure performed and type of work you are engaged in. Most people can return to office work within 2 weeks. Labour-intensive work however, may require you to take 4-6 weeks before returning to full duties.

When can I play after femoroacetabular impingement (FAI) surgery?

Low impact activities, such as cycling and swimming, can be commenced from week 4. If your procedure involves bone removal, high impact activities, such as running and jumping, they are best avoided for 6 weeks post-surgery. Sport-specific re-training can commence from week 6, with the aim to return to elite level sports 3 months post-surgery.

How long will I take to heal after femoroacetabular impingement (FAI) surgery?

The wounds take 7-10 days to heal. Most patients improve dramatically in the first 6 weeks. Occasionally, there are periods where the hip may become sore and then settle again. This is part of the normal healing process. It takes three months for your hip to fully recover from hip arthroscopy. Continued improvements may be gained up to 1 year post-surgery.

How much pain will I experience after femoroacetabular impingement (FAI) surgery?

Your experience of pain will vary depending on the procedure performed and the amount of pre-existing damage in the hip. Most patients are pleasantly surprised at how little pain they have after the procedure. Local anaesthetic is injected before and after the procedure to minimise any pain you may feel.

Will FAI return after femoroacetabular impingement (FAI) surgery?

The symptoms of FAI occur when impingement occurs between the ball and socket of your hip. Once the abnormal growth of bone in your hip joint has been removed, it is unlikely to grow back. The risk of ongoing damage to the hip is now low as the cause of FAI has been removed.

What are the risks of hip arthroscopy for the treatment of FAI?

Complications are not common but can occur. Prior to making any decision to have surgery, it is important that you understand the potential risks so that you can make an informed decision on the advantages and disadvantages of surgery. The following list is by no means exhaustive, so it is important to discuss your concerns with your your surgeon.

Some patients occasionally report numbness or tingling in the groin or inner thigh. This usually resolves with time. It is quite normal to experience some swelling and discomfort in the leg, thigh and buttock region. This is expected and will also resolve with time. It is important to avoid high impact activities during the early phase of recovery to minimise the risk of fracture.

Other general surgical risks include risk of infection, bleeding, and clots in the leg (DVT) or lung postoperatively.

Apart from the surgical risks, medical (including allergies) and anaesthetic complications can occur, and these can affect your general well-being and health.

FAORTHA FRACSInternational Society for Hip Arthroscopy


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