A Patient's Guide to Femoroacetabular Impingement Syndrome (FAI Syndrome)

FAI syndrome is a cause of hip and groin pain in active young adults. It is considered a movement problem, where there is early contact of the hip bones during movement. This occurs when there is a variation to the shape of the hip bones. In many individuals this does not give any problems (asymptomatic) but in some this can cause hip pain and stiffness.

The basic anatomy of the hip joint is shown below:

Your hip joint consists of a ball (femoral head) at the top of the thigh bone (femur), which fits into a socket (acetabulum) in your pelvis. There can be variations in the shape of the hip bones, involving the femoral head , the acetabulum or both.

Cam morphology is a cartilage or bony prominence (bump) of varying size, at any location around the femoral head-neck junction, which affects the round shape of the femoral head. This the most common variation in hip shape.

Pincer morphology refers to a deeper hip socket or extra bony prominence on the hip socket (acetabulum) or a change to the orientation of the hip socket.

There can be a combination of both cam and pincer morphology which is called mixed morphology.

Sometimes change variations in the shape of the hip bones causes increased load through the hip cartilage and labrum. This can sometimes result in tears of the labrum.

Primary cam morphology develops in young and active individuals, including athletes and is more common in males.

It likely develops during childhood and adolescence when the skeleton is developing and maturing. During this time the bones continue to grow and change shape. The growth plates, which are at the end of the bones, are affected by the load and rotational forces that the hip is exposed to during sporting activities. Primary cam morphology, a bony bump, is a normal physiological response to physical load. It is not associated with any previous injury or disease.

Conditions such as Legg-Calve Perthes disease and Slipped Capital Femoral Epiphysis can increase the likelihood of variations in the shape of the hip bones. Cam morphology that develops as a result of this, as this is associated with a previous condition, is referred to as secondary cam morphology.

The common symptoms from FAI syndrome are:

• Deep pain in the front of the hip or groin. It can sometimes cause pain in the outer hip and back of the hip and thigh.
• Stiffness of the hip
• Hip pain at end of motion
• Pain on squatting, sitting, lunging
• If the hip is irritable there can be night pain

Clicking, catching, locking and giving-way of the hip can occur in some people.

In most cases your doctor or physiotherapist will suspect FAI syndrome from your symptoms and also from a number of tests on the physical examination of your hip.

For FAI syndrome to be confirmed there needs to be all 3 elements:

• Clinical symptoms
• Clinical signs

The common symptoms from FAI syndrome are:

• Deep pain in the front of the hip or groin. It can sometimes cause pain in the outer hip and back of the hip and thigh.
• Stiffness of the hip
• Hip pain at end of motion
• Pain on squatting, sitting, lunging
• If the hip is irritable there can be night pain

Clicking, catching, locking and giving-way of the hip can occur in some people.         

In most cases your doctor or physiotherapist will suspect FAI syndrome from your symptoms and also from a number of tests on the physical examination of your hip.

For FAI syndrome to be confirmed there needs to be all 3 elements:

• Clinical symptoms

Clinical signs:

• Variations to the shape of the hip bones on imaging

It is common to have changes to the shape of the hip bones with no symptoms.

If a person does not have symptoms, they do not have FAI syndrome, even if they have imaging findings typically seen in FAI syndrome

Recent evidence suggests that both physiotherapy and surgery can be helpful in the management of symptomatic FAI syndrome.

Exercise-based physiotherapy should be the first line treatment for at least 3 months duration.

Treatment consists of:

1. Activity modifications to manage the load to the hip joint and reduce the irritability of your symptoms
2. An exercise programme, tailored to improve the control and strength of the muscles around the trunk, hips and pelvis
3. Exercises to improve function and balance
4. Hip joint movement optimisation
5. Exercises to support a graded return to sport and function
6. Exercises to improve cardio-vascular fitness                                                                                                                                                                                                                                                             If you feel that you are not improving with physiotherapy, it is important to discuss this with your therapist and you will be reviewed by a member of the surgical team. Your surgeon will discuss if surgery is a potential option for you and to discuss the risks and benefits specific to your situation.

Activity Modifications

Each person with FAI syndrome is individual. To reduce your symptoms, it may be appropriate that your therapist will discuss activity modifications regarding your work and leisure activities.  

Your therapist may also discuss weight management, smoking cessation and diet as lifestyle changes to support your health.

For further information, please see the NHS website ‘Live well’ pages.

Understanding what positions aggravate your problem can significantly help your symptoms. Some suggestions are described below:

Sitting

Try and reduce the time spent sitting on low chairs. Aim to sit with the hips higher than the knees, using a wedge cushion may help this.

If you have a desk based job, consider a sitting-standing desk to change your position regularly.

Sleeping

Sleeping with a pillow between your knees can be helpful to support the sore hip if it is irritable.

Another sleeping position that can be helpful is semi prone, halfway between lying on your tummy and your side.

Again, pillows can be used to support the top leg and in front of the trunk to avoid rolling fully onto your tummy and the underside leg can be straightened.

Exercises:

As each person with FAI syndrome is individual, your therapist will advise you on an exercise programme specific to your functional ability and needs.

FAI symptoms can improve over several months with physiotherapy-led exercise and modification of irritable positions and activities.

If surgery is appropriate, this can also improve FAI symptoms, however, to maximise your recovery this should be done together with a physiotherapy-led exercise programme.

In some cases, physiotherapy and surgery do not achieve full, pain free hip movement and function.

Injections

Corticosteroid injection (CSI) can be used to help with FAI symptoms with evidence showing short-term effect on symptoms.

Agricola et al 2012. Cam impingement causes osteoarthritis of the hip: a nationwide prospective cohort study (CHECK). Ann Rheum Dis 2012;0:1–6. doi:10.1136/annrheumdis-2012-201643

Agricola et al 2013. Pincer deformity does not lead to osteoarthritis of the hip whereas acetabular dysplasia does: acetabular coverage and development of osteoarthritis in a nationwide prospective cohort study (CHECK). Osteoarthritis and Cartilage 21 (2013) 1514e1521

Dijkstra et al 2022. Oxford consensus on primary cam morphology and femoroacetabular impingement syndrome: part 1—definitions, terminology, taxonomy and imaging outcomes. Br J Sports Med 2023;57:325–341. doi:10.1136/bjsports-2022-106085