Femoroacetabular Impingement
What Is Femoroacetabular Impingement (FAI)?
Femoroacetabular impingement (FAI) is abnormal contact between the femoral head (the ball) and the rim of the acetabulum (the socket) during movement, caused by small differences in the shape of the bones that form the hip. This contact pinches the labrum and cartilage at the rim of the joint, particularly in movements that flex and internally rotate the hip.
Over time this repeated impingement can lead to a labral tear and cartilage damage and, if left untreated, can set the stage for early hip arthritis. FAI is most often seen in young, active people. For general information about hip problems you can review the hip page.
Types of FAI: Cam, Pincer and Combined
- Cam type: the junction of the femoral head and neck is not perfectly round; it cannot rotate smoothly within the acetabulum and grinds against the cartilage at the rim. It is seen more often in young male athletes.
- Pincer type: there is extra bone at the rim of the acetabulum; this rim crushes the labrum against the femoral neck.
- Combined type: cam and pincer deformities occur together, and this is the form most commonly seen in practice.
Causes and Risk Factors
The bone shape that leads to FAI usually develops during skeletal growth. Exercise does not cause FAI, but people who play intense sport may notice the symptoms earlier.
- The hip bones developing this shape during the growth years (especially for the cam type).
- High-demand sports in adolescence that repeatedly load the hip (football, hockey, martial arts).
- A family history of FAI or early hip problems, and its appearance after some developmental hip conditions.
Symptoms
Symptoms usually begin insidiously and are triggered by particular movements. The pain is felt mostly in the groin; patients sometimes describe its location by cupping a hand around the side of the hip in a C shape.
- Pain in the groin that can spread to the side of the hip and the thigh.
- Pain that increases with flexing and internally rotating the hip, and with squatting, twisting and pivoting.
- Stiffness after prolonged sitting and pain on standing up.
- In some patients, a sense of catching or locking and restricted movement.
Conditions That Can Be Confused With FAI
Groin and hip pain has many causes, and examination and imaging tell them apart. In hip dysplasia the problem is not impingement but a shallow acetabulum that undercovers the femoral head; the two sometimes occur together and their treatment approaches differ.
A labral tear usually accompanies FAI and is rarely the primary problem on its own. Athletic groin pain, strains of the abdominal and groin muscles, hip bursitis and pain referred from the lower back produce similar symptoms, so the diagnosis is made not by symptoms alone but by imaging that shows the structure of the hip.
Diagnosis: Examination and Imaging
Diagnosis begins with the history and physical examination. Several tests are used together to assess the location of the pain, the movements that provoke it and the range of motion.
- Impingement test: groin pain when the knee is drawn to the chest and the hip is internally rotated suggests FAI.
- X-ray: the bone shape of the femoral head-neck and the acetabular rim is assessed; cam and pincer findings can be seen.
- MRI (MR arthrography when needed): the most valuable study for showing the state of the labrum and cartilage.
- As an aid to diagnosis, a local anaesthetic injection into the joint can help tell whether the pain is coming from the hip.
Non-Surgical Treatment
Treatment usually begins with non-surgical measures. The aim is to reduce the mechanics that provoke the pain and to improve the support of the muscles around the hip.
- Activity modification: temporarily limiting the movements that deeply flex and rotate the hip and provoke pain.
- Physiotherapy: a programme that strengthens the hip and trunk (core) muscles and improves movement control.
- Short-term anti-inflammatory medication under medical advice to manage pain and inflammation.
Intra-articular injections can help with diagnosis and temporary relief in selected cases, but they do not change the bone shape that causes the impingement. If symptoms persist despite non-surgical treatment, surgery is considered.
Exercise and Rehabilitation
The aim of physiotherapy is to support the joint with the muscles around the hip and to correct the movement patterns that increase impingement. The programme is individualised to the patient's symptoms, and movements that force painful deep flexion and rotation are avoided.
- Strengthening the hip abductors and the muscles at the back of the hip to improve pelvic control during walking and squatting.
- Core stabilisation work targeting the trunk and abdominal muscles.
- Range-of-motion and flexibility exercises in directions that do not pinch the hip.
- Reviewing and adjusting sport-specific movement technique.
Surgical Treatment: Arthroscopy
Surgery comes onto the agenda in patients whose symptoms persist despite non-surgical treatment and in whom imaging shows a structural problem with labral and cartilage damage. In most cases today hip arthroscopy is preferred.
In arthroscopy the joint is entered through small incisions with a camera and instruments; the excess bone is trimmed to reshape the femoral head-neck and the acetabular rim (osteoplasty), and the torn labrum is repaired or refixed. In advanced or complex deformities open surgery may be needed in selected cases. The aim of surgery is to reduce symptoms and slow the progression of joint damage; if the damage is advanced it may not be fully resolved by surgery and hip arthritis can develop.
Recovery and Return to Sport
In the early period after arthroscopy, weight-bearing is restricted with crutches and gradual range-of-motion work is carried out. Physiotherapy begins early to restore muscle strength and movement control.
Return to sport is guided by criteria such as pain-free movement, the recovery of muscle strength and controlled movement quality rather than by a fixed date. Recovery time varies with the procedure performed and any accompanying repairs.
When Should You See a Doctor?
Having hip pain assessed early widens the treatment options while the labrum and cartilage are still preserved.
- Your groin pain has lasted for several weeks and increases with squatting, twisting or prolonged sitting.
- You feel catching, locking or a marked restriction of movement in the hip.
- You play active sport and hip pain is affecting your performance and daily life.
To have your hip assessed you can contact Assoc. Prof. Serkan Sürücü, and you can also review the other conditions covered within hip surgery.