FAI Impingement

Clinical Physical Therapy Guide: Femoroacetabular Impingement (FAI)

Femoroacetabular Impingement (FAI) is a common, yet often underdiagnosed, condition characterized by abnormal contact between the femoral head/neck junction and the acetabular rim. This mechanical conflict leads to repetitive microtrauma to the articular cartilage and labrum, resulting in hip pain, stiffness, and potentially predisposing individuals to early onset osteoarthritis. As physical therapists, understanding the nuances of FAI is crucial for effective diagnosis, conservative management, and post-operative rehabilitation.

1. Overview of FAI Impingement

FAI is categorized into three primary types: Cam, Pincer, and Mixed. Each type involves a specific morphological abnormality contributing to the impingement:

• Cam Impingement: An abnormal shape of the femoral head and neck junction causes the femoral head to abnormally buttress against the acetabular rim, particularly during hip flexion and internal rotation. Common in active young males.
• Pincer Impingement: Characterized by an abnormality of the acetabulum, specifically an over-coverage of the femoral head by the acetabular rim. More prevalent in middle-aged women.
• Mixed Impingement: The most common presentation, combining features of both Cam and Pincer morphologies.

Patients typically present with deep anterior groin pain, often described as a "C-sign." Other symptoms include buttock pain, hip stiffness, clicking, locking, and pain exacerbated by prolonged sitting, walking, or activities involving hip flexion, adduction, and internal rotation (e.g., squatting, driving, sports activities). Early and accurate diagnosis, often confirmed with imaging, is vital to guide appropriate intervention and prevent progressive joint damage.

2. Functional Anatomy of the Hip Joint

The hip joint is a highly stable ball-and-socket joint, designed for both mobility and weight-bearing. Understanding hip anatomy is fundamental for FAI mechanics and rehabilitation.

• Bony Structures:
  • Femur: The femoral head articulates with the acetabulum. The femoral neck connects the head to the shaft. Abnormalities here contribute to Cam impingement.
  • Acetabulum: A concave socket providing coverage for the femoral head. Its shape and orientation are crucial; over-coverage or retroversion can lead to Pincer impingement. The acetabular labrum, a fibrocartilaginous ring, deepens the socket and provides stability.
• Muscular Support:
  • Hip Flexors: Iliopsoas, rectus femoris, sartorius. Tightness can exacerbate impingement.
  • Hip Extensors: Gluteus maximus, hamstrings. Critical for power and pelvic control.
  • Hip Abductors: Gluteus medius, gluteus minimus, tensor fasciae latae (TFL). Essential for frontal plane stability, preventing Trendelenburg, and femoral head centration. Weakness often contributes to poor biomechanics.
  • Hip Adductors: Adductor longus, brevis, magnus, pectineus, gracilis. Imbalances can affect pelvic alignment.
  • Deep External Rotators: Piriformis, gemelli, obturators, quadratus femoris. Contribute to dynamic stability and femoral head position.
• Ligaments: Strong capsular ligaments (iliofemoral, pubofemoral, ischiofemoral) provide static stability, limiting excessive motion.

Biomechanically, FAI occurs when certain hip movements, particularly combinations of flexion, adduction, and internal rotation, cause abnormal femoral-acetabular contact. Optimal lumbopelvic rhythm, core stability, and coordinated muscle activity are paramount. Dysfunction can alter hip kinematics and increase joint stress.

3. Four Phases of Rehabilitation for FAI Impingement

A structured, progressive rehabilitation program is the cornerstone of conservative FAI management, whether used as a primary treatment or post-operatively. The following four phases guide the patient from acute pain to full functional recovery.

Phase 1: Acute Pain Management & Protection (Weeks 0-2/4)

Goal: Reduce pain and inflammation, protect the healing joint (if post-op), restore basic pain-free range of motion (ROM), and initiate core/hip activation without impingement.

• Interventions:
  • Activity Modification: Educate patient on avoiding provocative movements (e.g., deep squats, prolonged sitting, crossing legs). Relative rest.
  • Pain Management: Modalities (ice, heat, electrical stimulation) as needed. Manual therapy for surrounding muscle spasm.
  • Gentle ROM: Pain-free hip flexion (limited), abduction, external rotation (e.g., supine heel slides).
  • Isometric Strengthening: Glute sets, quad sets, adductor squeezes, gentle TA bracing.
  • Neuromuscular Control: Pelvic tilts, supine hip marching.
  • Patient Education: Body mechanics for daily activities, joint protection strategies.
• Progression Criteria: Minimal pain, improved basic ROM, independent HEP, no impingement during controlled movements.

Phase 2: Restoration of Foundational Strength & Mobility (Weeks 2/4 - 6/8)

Goal: Improve pain-free hip ROM, enhance hip and core strength, re-educate optimal movement patterns, and address muscle imbalances.

• Interventions:
  • Continued ROM: Progress pain-free hip flexion and internal rotation within limits, focusing on controlled, non-impinging motion. Emphasize hip capsule mobility.
  • Hip Strengthening:
    • Glute Med/Min: Side-lying hip abduction, clam shells (banded), standing hip abduction, single-leg balance.
    • Glute Max: Glute bridges (double/single leg), quadruped hip extension.
    • Core Stability: Plank variations, bird-dog, dead bug, pallof presses.
    • Adductors/Deep Rotators: Adductor squeezes, seated hip external rotation with band.
  • Neuromuscular Control: Step-downs, mini-squats (controlled depth), lunges (small range), single-leg balance with reaches.
  • Soft Tissue Mobilization: Release tight hip flexors, TFL, piriformis, adductors.
• Progression Criteria: Good pain control, pain-free exercises, stable core, improved single-leg control, symmetrical strength, near full non-impinging ROM.

Phase 3: Advanced Strength, Power & Return to Activity (Weeks 6/8 - 12+)

Goal: Restore full functional strength, power, agility, and prepare the patient for demanding sport-specific or occupational activities while maintaining joint protection.

• Interventions:
  • Progressive Resistance Training:
    • Compound Movements: Squats (box, goblet, front), lunges (all planes), step-ups, modified deadlifts, hip thrusts.
    • Plyometrics (low-impact): Box jumps, pogo hops, skipping, medicine ball throws.
    • Single-Leg Progression: Single-leg RDLs, modified pistol squats, single-leg hops.
  • Agility & Sport-Specific Drills: Cone drills, shuttle runs, cutting drills, sport-specific movement patterns.
  • Advanced Core: Rotational planks, medicine ball chops, anti-rotation.
  • Endurance Training: Gradually increase duration/intensity of cardiovascular activities (e.g., cycling, elliptical, running progression).
• Progression Criteria: Pain-free with all functional/sport movements, symmetrical strength/power, excellent dynamic stability, good endurance, psychological readiness for return to activities.

Phase 4: Maintenance & Prevention (Ongoing)

Goal: Maintain long-term gains, prevent recurrence of symptoms, optimize performance, and integrate self-management strategies into daily life.

• Interventions:
  • Continued Strength & Conditioning: Regular strength training (2-3x/week) for hip, core, glutes.
  • Flexibility & Mobility: Ongoing stretching and mobility work to maintain pain-free ROM.
  • Activity Monitoring: Self-awareness of impingement-provoking activities and adjustment.
  • Cross-Training: Incorporate varied activities to maintain overall fitness without overloading the hip.
  • Education: Long-term injury prevention, proper warm-up/cool-down, nutrition, hydration.
  • Periodic Check-ins: Consider occasional PT follow-ups for re-assessment.
• Progression Criteria: Consistent adherence, symptom-free participation, ability to self-manage flare-ups.

4. Research and Clinical Evidence for FAI Management

FAI understanding has evolved. Research strongly supports conservative PT as first-line treatment for most symptomatic FAI. Structured rehab, focusing on hip/core strengthening, movement re-education, and activity modification, significantly reduces pain and improves function.

When conservative care fails, hip arthroscopy shows good outcomes. Post-operative rehab is critical, following a phased approach similar to conservative care but with initial protection. Research explores optimal post-op recovery parameters.

Long-term studies on FAI's role in hip osteoarthritis are ongoing. FAI is a risk factor, but the long-term impact of interventions on OA progression is under investigation. Individualized treatment, tailored to morphology, symptoms, and goals, is crucial. PTs play a pivotal role in evidence-based practice and guiding recovery.