Femoroacetabular Impingement

Other names for femoroacetabular impingement

• Femoroacetabular impingement syndrome
• FAI (Femoroacetabular Impingement)
• Cam or pinch hip

What is a femoroacetabular impingement?

Femoroacetabular impingement is abnormal contact between the head of the femur (thigh bone) and the rim of the acetabulum (hip socket). This friction causes irritation during certain movements, resulting in pain and limited mobility.

To understand this properly, imagine the hip joint as a ball that fits into a socket. The ball is the head of the femur. The socket is the acetabulum. Normally, this ball slides freely in the socket when you move. With a femoroacetabular impingement, there is a bony bump that prevents this smooth sliding.

This condition affects approximately 3% of adults aged 20 to 50. It is particularly common among athletes and active individuals.

If the conflict is not treated, repeated irritation can damage the cartilage and labrum (the ring of tissue surrounding the acetabulum). This increases the risk of developing hip osteoarthritis in the long term.

What are the types of femoroacetabular impingement?

There are three types of femoroacetabular impingement, depending on the location of the bone abnormality. The mixed type, which combines the two basic forms, accounts for 86% of cases.

Cam type is caused by a bump or excess bone at the junction between the head and neck of the femur. This bump prevents the femoral head from rotating freely in the acetabulum. It rubs against the rim during flexion and rotation movements.

Cam type is more common in young men, affecting 9 to 25% of them.

The pincer type is caused by excess bone coverage at the acetabulum. The rim of the "bowl" is too pronounced and pinches the femoral neck during certain movements.

The Pincer type is more common in middle-aged women, affecting approximately 19.6% of them.

The vast majority of people (86%) have a combination of both types. The treatment remains the same regardless of the type of conflict.

What causes femoroacetabular impingement?

Femoroacetabular impingement is mainly caused by the natural shape of your bones. The anatomy of your hip, determined during your growth, influences how the joint moves.

Some people develop a bone formation that causes friction during specific movements. This is not something you have "caused" through your activities.

However, certain factors can aggravate the situation:

• Repetitive hip movements with inadequate mechanics
• Too rapid an increase in training volume
• Sports requiring extreme hip range of motion

The good news is that even though the shape of your bones cannot change, physical therapy treatments can significantly improve your symptoms.

What are the risk factors?

Certain groups of people are more likely to develop femoroacetabular impingement. High-impact sports practiced intensively during adolescence are particularly associated with this condition.

• Ice hockey
• Soccer
• Basketball
• Dance (especially ballet)
• Martial arts

Repetitive hip flexion and rotation movements during bone growth can influence the development of bone shape.

Children who have had certain hip conditions are at greater risk:

• Hip dysplasia
• Congenital hip dislocation
• Legg-Calvé-Perthes disease

These conditions can affect the normal development of the hip joint.

What are the symptoms of femoroacetabular impingement?

The main symptom is groin pain, present in 83% of cases. This pain worsens during activities that involve hip flexion.

• Mainly in the groin (front of the hip)
• May radiate to the buttock
• May be felt on the side of the hip
• Sometimes in the thigh

• Running
• Walk with long strides
• Do squats (especially deep squats)
• Climbing stairs or hiking uphill
• Sitting for long periods of time (at work, in the car)
• Standing up from a seated position

• Stiffness and decreased hip mobility
• Sensations of cracking, clicking, or popping during certain movements
• Occasional jamming
• Difficulty putting on stockings or shoes

Some people with abnormalities visible on imaging have no symptoms. If you have no pain, you do not need treatment.

How is femoroacetabular impingement diagnosed?

The diagnosis is based on your symptom history and a clinical examination. The FADIR test (flexion-adduction-internal rotation) is particularly useful for reproducing your pain.

• Questions about the location and circumstances of your pain
• Assessing your hip mobility
• Specific tests to reproduce the conflict
• Assessment of stabilizing muscle strength

X-rays can confirm the diagnosis by showing the shape of the bones. Your healthcare provider can measure:

• The alpha angle (shape of the femur)
• The center-edge angle (acetabular coverage)

An MRI may be requested to assess the condition of the labrum and cartilage if surgery is being considered.

When should you see a physical therapist?

Consult a physical therapist if you experience the symptoms described above or if your doctor has already ruled out other possible causes of your hip pain.

You do not need to see a doctor before consulting a physical therapist. If your condition requires medical attention, your physical therapist will be able to advise you and refer you to a doctor.

• You have groin pain that has persisted for more than 2 weeks.
• Pain limits your sports or daily activities
• You have difficulty sitting down or standing up
• You feel a sense of blockage in your hip

Conservative treatment (physical therapy and exercises) is the recommended first line of treatment. Surgery is rarely necessary and is only considered after conservative treatment has failed.

What are the physiotherapy treatments?

Physiotherapy treatment aims to reduce irritation and improve muscle control of the hip. Studies show that 70% of patients can be treated successfully without surgery.

Your physical therapist will conduct a comprehensive assessment to identify the factors contributing to your conflict:

• Your joint mobility
• The gliding of your nerves
• The quality of your movements
• Your muscle strength and stability
• Your movement patterns during your activities

Based on the results of the assessment, your physical therapist will be able to:

• Mobilize your hip to reduce pain and improve movement
• Give you exercises to strengthen your gluteal muscles and hip stabilizers
• Teaching you neuromuscular control exercises to improve the quality of your movements
• Helping you temporarily modify activities that irritate your hip
• Providing you with advice on your posture and everyday movements

A typical rehabilitation program lasts approximately 12 weeks, with 6 to 10 sessions with your physical therapist. Studies show that improvements are sustained over the long term, even after 5 years of follow-up.

What to do at home?

Temporarily reduce movements that increase your pain and avoid positions that compress the hip. Here are some practical tips:

• Swimming (all styles)
• Bicycle or stationary bike (well-adjusted seat)
• Elliptical trainer
• Moderate walking on flat terrain

• Standing with your hips swaying (putting your weight on one hip)
• Sit with your legs crossed
• Do deep squats
• Forcefully bring the knee toward the chest

If you are unable to sleep on your back, place a pillow between your thighs when lying on your side. This will keep your hips aligned.

• Incorporate walking breaks into your runs
• Temporarily reduce the intensity and volume of your training.
• Do glute strengthening exercises regularly.
• Avoid movements that reproduce your pain.

If you see no improvement after 10 to 14 days of modifying your activities, consult a physical therapist.

How long does it take to heal?

Most people see significant improvement within 8 to 12 weeks with appropriate physical therapy treatment. Continuing with the exercises is important for long-term success.

• How long have you had symptoms (more recent = faster)
• Your adherence to the recommended exercises
• Your level of physical activity
• The severity of your conflict

Studies show that the improvements achieved with physical therapy are maintained even after 5 years. The secret is to continue your strengthening exercises even after your symptoms have disappeared.

Surgery (hip arthroscopy) is only considered if conservative treatment has not worked after at least 2 months of consistent effort. The vast majority of people will not need surgery.

Sources

• Paris Physical Therapy Institute. Femoroacetabular impingement. Prevalence study in Canada.
• Kuhns BD, et al. Femoroacetabular Impingement. StatPearls [Internet]. 2024.
• Clinical source: Physioactif.
• Cleveland Clinic. Hip Impingement (Femoroacetabular Impingement or FAI).
• Agricola R, et al. The Prevalence of Cam and Pincer Morphology and Its Association With Development of Hip Osteoarthritis. J Orthop Sports Phys Ther. 2018;48(4):230-238.
• Kemp JL, et al. Optimizing Conservative Treatment for Femoroacetabular Impingement Syndrome: A Scoping Review. Applied Sciences. 2025;15(5):2821.
• Femoroacetabular Impingement: Critical Analysis Review of Current Nonoperative Treatments. PMC. 2024.
• Griffin DR, et al. The FASHIoN trial: personalized hip therapy. Lancet. 2018.
• British Hip Society. Conservative Treatment for Femoro-Acetabular Impingement Syndrome. Guidelines 2024.