FABER Test: Understanding, Performance, and Interpretation

What is the FABER test?

The FABER test, an acronym for Flexion, Abduction, and External Rotation, is a common orthopedic assessment used to evaluate the hip joint and sacroiliac (SI) joint for pathology, pain, or restricted range of motion.

Understanding the FABER Test

The FABER test, also known as Patrick's test, is a provocative maneuver designed to stress the hip and sacroiliac joints. It is a widely utilized screening tool in physical therapy, sports medicine, and chiropractic practice to help identify potential sources of pain or dysfunction in the hip and pelvic region. Its utility lies in its ability to simultaneously challenge several key structures, providing valuable diagnostic clues.

Purpose and Clinical Relevance The primary purpose of the FABER test is to:

• Assess for hip joint pathology, such as osteoarthritis, femoroacetabular impingement (FAI), labral tears, or capsular tightness.
• Evaluate for sacroiliac joint dysfunction or inflammation.
• Identify iliopsoas or adductor muscle tightness or pathology.

Acronym Breakdown The name FABER precisely describes the sequence of movements the hip joint undergoes during the test:

• Flexion: The hip is flexed.
• ABduction: The hip is moved away from the midline.
• External Rotation: The hip is rotated outwards.

Anatomy and Biomechanics Involved

Performing the FABER test places specific stresses on the anatomical structures around the hip and pelvis. A thorough understanding of these structures is crucial for accurate interpretation.

Key Joints

• Femoroacetabular Joint (Hip Joint): A ball-and-socket joint where the head of the femur articulates with the acetabulum of the pelvis. The FABER position maximally stresses the anterior and superior aspects of the hip capsule and joint surfaces.
• Sacroiliac (SI) Joint: The joint formed between the sacrum and the ilium. The forces generated during the FABER test, particularly with overpressure, can induce movement or stress across this joint.

Muscles Stretched/Involved The FABER position effectively stretches several muscle groups and challenges others:

• Adductor Muscles: (e.g., adductor longus, brevis, magnus, gracilis, pectineus) are stretched as the hip is abducted.
• Hip Flexors: (e.g., iliopsoas) are placed in a shortened, potentially compressed, position.
• External Rotators: (e.g., piriformis, gemelli, obturators, quadratus femoris) are engaged to achieve the external rotation.
• Gluteal Muscles: (e.g., gluteus medius, minimus) are also involved in stabilizing the hip.

Ligaments and Capsule The hip joint capsule, along with its reinforcing ligaments (iliofemoral, pubofemoral, ischiofemoral), are subjected to tension during the FABER maneuver, particularly the anterior and superior portions. The SI joint ligaments are also stressed, especially when overpressure is applied to provoke pain from that region.

How to Perform the FABER Test

Proper execution of the FABER test is critical for reliable results. It should always be performed bilaterally for comparison.

Patient Positioning

• The patient lies supine (on their back) on an examination table.
• Ensure the patient is relaxed and comfortable, with their spine in a neutral position.

Test Execution

1. Figure-4 Position: The examiner passively flexes the hip of the tested leg, abducts it, and externally rotates it so that the ankle of the tested leg rests on the contralateral (opposite) knee, forming a "figure-4" shape.
2. Stabilization: Place one hand on the anterior superior iliac spine (ASIS) of the contralateral hip to stabilize the pelvis and prevent compensatory movement.
3. Overpressure Application: With the other hand, gently apply downward pressure to the medial aspect of the tested knee. The goal is to lower the knee towards the examination table, further abducting and externally rotating the hip.
4. Observation and Assessment: Observe the range of motion and note any reproduction of pain. Compare the range of motion and pain response to the unaffected side.

Important Considerations

• Patience Comfort: Always monitor the patient's comfort level and stop if excessive pain is elicited.
• Controlled Movement: Perform the movement slowly and controlled, avoiding sudden jerks.
• Bilateral Comparison: Always compare findings to the unaffected side, as normal range of motion can vary between individuals.
• End-feel: Note the end-feel of the movement (e.g., soft, firm, empty due to pain).

Interpreting FABER Test Results

The interpretation of the FABER test depends on the location of the pain elicited and the observed range of motion.

Positive Test Indications A positive FABER test typically involves the reproduction of the patient's chief complaint of pain or a significant limitation in range of motion compared to the unaffected side. The location of the pain provides critical clues:

• Anterior Hip Pain (Groin or Front of Hip): This often indicates pathology within the hip joint itself. Possible causes include:
  • Femoroacetabular Impingement (FAI), particularly cam or pincer type.
  • Hip osteoarthritis.
  • Labral tears of the hip.
  • Capsulitis or synovitis.
  • Iliopsoas tendinopathy or bursitis (though this can also present as groin pain).
• Posterior Hip or Sacroiliac (SI) Joint Pain: Pain felt in the buttock or directly over the SI joint suggests SI joint dysfunction or inflammation. This is often due to the rotational stress applied across the SI joint during the test.
• Lateral Hip Pain: Less common, but can indicate trochanteric bursitis or gluteal tendinopathy, though other tests are more specific for these conditions.
• Limited Range of Motion (without significant pain): If the tested knee remains significantly elevated from the examination table compared to the other side, it may indicate:
  • Hip capsular tightness (e.g., post-surgical stiffness, long-standing arthritis).
  • Tightness of hip adductor muscles.
  • Bony blockages (osteophytes) within the hip joint.

Negative Test A negative FABER test means that the patient experiences no pain, and the tested knee can drop to a similar level as the contralateral side, indicating normal or symmetrical hip and SI joint mobility without provocation of symptoms.

Limitations and Considerations

While a valuable screening tool, the FABER test has limitations and should not be used in isolation for diagnosis.

Not Diagnostic Alone The FABER test is a provocative test, meaning it attempts to reproduce symptoms. A positive test indicates that a particular structure or area is likely involved, but it does not provide a definitive diagnosis on its own. It should always be part of a comprehensive orthopedic assessment that includes:

• Detailed patient history.
• Other physical examination tests (e.g., FADIR test, scour test, palpation).
• Neurological screening.
• Imaging studies (X-ray, MRI) if indicated.

Specificity vs. Sensitivity The FABER test has varying levels of sensitivity and specificity for different conditions. For instance, it is generally considered sensitive for hip joint pathology and SI joint dysfunction, meaning it's good at ruling out these conditions if negative, but a positive result needs further investigation to rule in a specific diagnosis.

Patient Factors Results can be influenced by:

• General Flexibility: Highly flexible individuals may have a greater range of motion without pathology.
• Pain Tolerance: Patient's pain threshold can affect their reported discomfort.
• Acute Injury: In cases of acute injury, even light pressure can elicit severe pain, making interpretation challenging.

Conclusion

The FABER test is an indispensable component of the orthopedic physical examination for evaluating the hip and sacroiliac joints. By understanding its biomechanical principles, proper execution, and the nuances of interpreting its results, clinicians can effectively utilize this tool to narrow down potential sources of pain and guide further diagnostic and therapeutic interventions. Remember, the FABER test is a piece of the puzzle; a comprehensive assessment by a qualified healthcare professional is always necessary for an accurate diagnosis and appropriate treatment plan.