Hip Impingement Femoroacetabular Impingement: Symptoms, Types, Causes and Treatment

Femoroacetabular impingement (FAI), commonly known as hip impingement, is increasingly recognized as a key cause of hip pain and early osteoarthritis, especially in young and active individuals. Understanding FAI is essential for anyone experiencing persistent hip discomfort, athletes striving to return to play, or clinicians seeking the best intervention for their patients. In this comprehensive review, we'll walk you through FAI's symptoms, types, causes, and the latest evidence-based treatment options.

Symptoms of Hip Impingement Femoroacetabular Impingement

Hip impingement doesn’t always announce itself loudly at first. For many, the symptoms can be subtle, gradually interfering with daily life or athletic performance. Recognizing these early signs is crucial for timely diagnosis and management.

Symptom	Description	Typical Population	Source(s)
Groin Pain	Deep, aching pain in anterior groin, often worse with sitting or activity	Young adults, athletes	4 5 10
Limited Motion	Reduced hip flexion and internal rotation	Adolescents, adults	2 3 5 7
Activity Pain	Sharp pain during or after sports or prolonged sitting	Active individuals	4 5 10
Mechanical Signs	Clicking, locking, or catching sensations	Various	3 5

Table 1: Key Symptoms

Groin Pain: The Classic Signal

The hallmark of FAI is chronic, deep, or aching pain in the anterior groin. This discomfort often intensifies when sitting for long periods, during high-impact sports, or after vigorous activity. Occasionally, patients report sudden sharp pains, especially with rotational movements of the hip. This pain typically worsens with activity and may radiate to the lateral thigh or buttock in some cases 4 5 10.

Reduced Range of Motion

A distinctive feature of FAI is a gradual loss of hip flexibility, particularly flexion and internal rotation. Patients often notice they can’t move their hip as freely as before. This is especially pronounced in activities like squatting, running, or pivoting 2 3 5 7.

Pain During Activity and Mechanical Symptoms

FAI symptoms often flare up during or after sports, dancing, or other activities involving repetitive hip movement. Some individuals hear or feel a “click,” “catch,” or experience locking in their hip, which may hint at labral injury or cartilage damage 3 5.

Physical Examination Findings

Doctors use specific tests, like the anterior impingement test (flexing the hip to 90 degrees and rotating it inward), which reliably reproduces the pain seen in FAI. A positive test, along with limited motion and imaging findings, is a strong indicator of the condition 2 4 5.

Types of Hip Impingement Femoroacetabular Impingement

FAI isn’t a one-size-fits-all diagnosis. There are distinct types, each with unique anatomical features and patterns of joint damage. Understanding these differences is key to effective management.

Type	Defining Feature	Damage Pattern	Source(s)
Cam	Non-spherical femoral head/neck	Shearing of cartilage, labral detachment	1 3 4 9 7
Pincer	Excessive acetabular coverage	Labral crushing, rim ossification	1 3 4 9 5
Mixed	Combination of cam and pincer anomalies	Combined cartilage and labral damage	2 5 9

Table 2: FAI Types and Features

Cam Type FAI

Cam impingement is characterized by a non-spherical femoral head or a bony bump at the femoral neck. This abnormal shape leads to abnormal contact with the acetabular (hip socket) rim during hip motion, particularly flexion and rotation. The result? Shearing off of the acetabular cartilage and detachment of the labrum from the cartilage, mostly at the anterosuperior part of the hip joint 1 3 4 9.

• More common in young men and athletes 7
• Associated with decreased internal rotation 2 7
• Leads to early cartilage damage

Pincer Type FAI

Pincer impingement occurs when there is excessive coverage of the femoral head by the acetabulum. This can be due to variations like acetabular retroversion or a deep socket. Here, the labrum gets pinched between the rim of the acetabulum and the femoral neck, resulting in labral degeneration, ossification, and a narrow strip of cartilage damage 1 3 4 9 5.

• More prevalent in women and adolescent females 5
• Damage is more circumferential and affects the labrum more than cartilage

Mixed Type FAI

Most patients don’t fit neatly into one category. Mixed FAI—a combination of cam and pincer abnormalities—is actually the most common presentation. Mixed impingement causes both cartilage and labral damage, with symptoms and physical findings of both types 2 5 9.

Causes of Hip Impingement Femoroacetabular Impingement

Why do some people develop FAI while others don’t? The answer lies at the crossroads of anatomy, genetics, activity, and development.

Cause	Mechanism	Risk Factors	Source(s)
Morphology	Abnormal femoral head/neck or acetabulum	Genetics, growth, activity	1 3 4 6 7 9
Repetitive Motion	High-impact or repetitive hip flexion	Sports, dance, athletics	5 10
Genetics	Familial predisposition to abnormal bone shape	Family history	6 7
Development	Growth plate and developmental disorders	Childhood hip disease	6 7

Table 3: Underlying Causes

Anatomical Abnormalities

The root of FAI is structural—abnormal shapes of the hip joint bones. Cam FAI arises from a misshapen femoral head/neck, while pincer comes from acetabular overcoverage. These may be present from adolescence but are often silent until repetitive movements bring about pain and injury 1 3 4 6 7 9.

Activity and Repetitive Motion

FAI is more common in people who participate in activities that demand repetitive hip flexion and rotation, such as soccer, hockey, dancing, and martial arts. These movements can exacerbate underlying anatomical variations, accelerating damage to the cartilage and labrum 5 10.

Genetic and Developmental Factors

There’s increasing evidence that genetics play a role in hip bone shape. FAI is more prevalent in close relatives of affected individuals. Also, developmental disorders affecting the hip during childhood can predispose to impingement in later years 6 7.

Other Contributing Factors

• Decreased femoral version: Altered orientation of the femoral neck can change impingement zones and reduce hip mobility 2.
• Acetabular retroversion: A backward-tilted socket increases the likelihood of pincer impingement 5.

Treatment of Hip Impingement Femoroacetabular Impingement

Management of FAI ranges from conservative approaches to advanced surgical interventions. The choice depends on severity, patient age, activity level, and the degree of joint damage.

Treatment	Purpose/Effect	Best for	Source(s)
Activity Modification	Reduce hip stress, ease pain	Early/mild cases	4 10
Physical Therapy	Improve strength, mobility	Most cases	4 10 11
Medications	Control pain and inflammation	Adjunctive therapy	4 10
Hip Arthroscopy	Reshape bones, repair labrum	Persistent/severe	1 8 11 12 13 14
Open Surgery	Complex or advanced cases	Advanced deformity	1 12 13

Table 4: FAI Treatment Options

Conservative Management

For many, the first steps are non-surgical:

• Activity modification: Avoiding positions and activities that provoke pain.
• Physical therapy: Focused on strengthening core and hip muscles, improving flexibility, and restoring normal movement patterns.
• Medications: Nonsteroidal anti-inflammatory drugs (NSAIDs) for pain relief as needed 4 10 11.

Personalized hip therapy, supervised by a physiotherapist, can significantly improve quality of life, though improvements may be less dramatic than surgery for some patients 11.

Surgical Treatment

When conservative measures fail or if there is significant structural damage, surgery may be recommended.

Hip Arthroscopy

Hip arthroscopy is minimally invasive and is now the most common surgical approach for FAI. Surgeons reshape the femoral head/neck (cam) or acetabular rim (pincer), and repair or refix the labrum as needed 8 13 14.

• Outcomes: Most patients experience significant improvements in pain, function, and return to sport. Complication and reoperation rates are low 8 14.
• Labral repair and capsular closure are increasingly performed, as they are associated with better outcomes and lower rates of conversion to hip replacement 14.
• Return to activity: Over 85% of patients can return to sport after arthroscopy 8.

Open Surgical Approaches

For severe deformities or when arthroscopy isn’t feasible, open surgical hip dislocation allows comprehensive reshaping and labral repair 12 13. Good results are seen in early-stage osteoarthritis, but advanced cartilage damage may require hip replacement 12.

Comparative Effectiveness

Randomized trials show that both hip arthroscopy and physiotherapist-led care improve patient-reported quality of life, but surgery offers a greater magnitude of improvement in the short term 11.

Risks and Complications

Surgical risks are generally low but can include infection, nerve injury, or the need for further surgery. The rate of conversion to total hip arthroplasty (joint replacement) remains under 10% in most series, especially with modern techniques emphasizing soft tissue preservation 14.

Conclusion

Femoroacetabular impingement is a complex, yet increasingly understood, cause of hip pain and dysfunction—especially in younger, active people. Here’s what you need to remember:

• Symptoms: Deep groin pain, reduced hip motion, activity-related pain, and mechanical sensations are common warning signs.
• Types: FAI is categorized as cam, pincer, or mixed, each with distinct anatomical features but often overlapping.
• Causes: The condition stems from structural bone abnormalities, often influenced by genetics, developmental factors, and repetitive motion.
• Treatment: Initial management is conservative, but hip arthroscopy offers excellent outcomes for persistent or severe cases, with an increasing focus on labral preservation and capsular repair.

Key Takeaways:

• Early recognition and intervention can prevent or delay progression to osteoarthritis.
• Most patients achieve significant pain relief and can return to sports after appropriate treatment.
• Both non-surgical and surgical options are effective; treatment should be tailored to individual needs and disease severity.

If you or someone you know is struggling with hip pain, timely evaluation and evidence-based care can make all the difference for long-term hip health.