Femoroacetabular impingement (FAI)

Figure 2: Hip pain - FAI - Physio Frenchs Forest, Physio Macquarie Park

Femoroacetabular impingement (or FAI) is a classification of hip pain, caused by the unusual contact of the pelvis and the femur (the large bone of the upper leg), where they meet at the hip joint. 

Relevant Anatomy:

The hip joint is a very deep and stable ball and socket joint. The ball (the femur) fits snuggly into the socket (the pelvis), and is held in place by a number of strong ligaments, as well as a thick joint capsule, for extra security. A ring of fibrocartilage, called the labrum, also runs around the rim of the socket (or acetabulum), providing a deeper and more secure socket for the femur to articulate in. 

Clinical Presentation:

A patient suffering from FAI Syndrome will likely present with:

• Stiffness or pain in the hip, groin (or both regions simultaneously) 

• Pain that is aggravated by climbing stairs, sitting for prolonged periods of time, or exercises such as squats

• Restricted range of motion at the hip joint 

• Catching, locking or giving way of the hip joint reported by the patient

A number of potential causes have been listed in the literature, including:

• Genetic factors

• Repetitive hip flexion or rotation, especially during a person’s developmental years

• Previous childhood hip conditions, such as hip dysplasia or Perthes Disease

• Incorrect healing of previous femoral fractures

• Retroversion and anteversion of the hip

Figure 2: Hip pain - FAI - Physio Frenchs Forest, Physio Macquarie Park

Mechanism of Injury:

Femoroacetabular Impingement is created by changes in the shapes of the bones at the hip joint, causing an atypical contact between the femur and the pelvis. There are three classifications of these bony changes:

1. CAM Morphology - due to bony growth, the ball of the femur widens and becomes flatter, affecting the way the femur articulates in the acetabulum (or socket of the pelvis). This presentation is more common in males.

2. Pincer Morphology - again due to bony growth, the socket of the hip extends further around the femur than normal, causing the two bones to contact much earlier through range of motion than normal. This presentation is more common in females. 

3. Combination Morphology - a combination of the above two presentations is seen on imaging, such as x-ray. 

It is important to mention that findings similar to those listed above are found in up to 30% of the general population, even in patients with no hip pain. Therefore, a trio of presenting symptoms, clinical signs and findings on imaging must all be present for a diagnosis of FAI Syndrome to be confirmed. 

What is the treatment of FAI?

Conservative/Physiotherapy:

• Education for the patient: We outline the likely causes of action and outcomes. This includes the fact that after 2 years, there are no significant differences in outcome measures between surgical and conservative approaches. We advise exercises and activities to avoid that may be the cause of the hip irritation. These exercises include deep squats, lunges, and ensuring the feet are point in the right direction with squats.

• A progressive, unique exercise program is prescribed to the patient, focussing on improving strength and neuromuscular control at the hip joint, and of the surrounding areas. Particularly patients should look at increasing the stregnth of the glutues medius muscle. This muscle due to its unique anatomy will help stabilise the hip in the ball and socket joint. Exercises include clams, hip abduction, crab walks and single leg exercises.

• Any patient looking to return to a particular sport or activity is also recommended to undergo sport-specific strengthening drills, to ensure they are ready to undergo the demands of their chosen activity. 

• Surgical interventions for FAI are not common, and the literature is weak, and in certain cases the symptom relief is only short-term. Arthroscopy (a minimally invasive surgery, using small incisions) is the most common surgical technique used to treat FAI. Arthroscopy consists of reshaping the ball and socket of the hip joint, as well as repairing or removing any damaged segments of the cartilage around the hip joint. 

See our expert Physiotherapy team at Frenchs Forest and Macquarie Park!