What does a positive FABER (Flexion, Abduction, and External Rotation) test indicate?

Positive FABER Test Interpretation

A positive FABER (Flexion, Abduction, External Rotation) test indicates hip-related pain and suggests the presence of intra-articular hip pathology, including femoroacetabular impingement (FAI) syndrome, acetabular dysplasia/hip instability, or labral/chondral/ligamentum teres pathology in young and middle-aged active adults. 1

Primary Diagnostic Considerations

When the FABER test is positive, the following conditions should be considered:

Hip-Related Pain Categories

• FAI syndrome - characterized by symptomatic premature contact between the proximal femur and acetabulum, often with cam, pincer, or mixed morphology 1
• Acetabular dysplasia and/or hip instability - structural abnormalities affecting hip stability 1, 2
• Soft tissue pathology without distinct bony morphology - including labral tears, chondral lesions, and ligamentum teres conditions 1

Clinical Performance Characteristics

• The FABER test demonstrates 88% positivity rate in patients with confirmed hip joint pathology 3
• When combined with groin as the main location of pain, sensitivity increases to 0.97 for detecting FAI and labral pathology 4
• A positive FABER distance test (≥4 cm difference between hips) correlates with higher alpha angles (average 74° vs 68°) and has 85% sensitivity for pathological cam-type FAI 5

Diagnostic Algorithm

Initial Clinical Assessment

• Groin pain as primary symptom - most common presentation requiring evaluation 4
• Restricted and painful hip quadrant compared to contralateral side - consistently positive finding 3
• FABER distance measurement - quantify difference between affected and unaffected hip (≥4 cm suggests cam morphology) 5

Mandatory Exclusions

Before attributing symptoms to hip-related pain, exclude:

• Non-musculoskeletal conditions - tumors, infections 1, 2
• Serious hip pathology - stress fractures, slipped capital femoral epiphysis 1
• Competing musculoskeletal sources - lumbar spine pathology, which commonly coexists 1, 2

Imaging Recommendations

First-Line Imaging

• AP pelvis and lateral femoral head-neck radiographs are the recommended initial imaging modality 1, 2
• Plain radiographs assess for bony morphology including alpha angle and center-edge angle measurements 1

Advanced Imaging Indications

• MRI or MRA when three-dimensional morphological assessment is needed or to evaluate intra-articular structures (labrum, cartilage, ligamentum teres) 1, 2
• Critical caveat: Imaging must always be combined with clinical symptoms and signs, never used in isolation 1, 2
• Incidental labral and chondral findings are common in asymptomatic individuals and should not drive treatment decisions alone 1

Important Clinical Pitfalls

Test Limitations

• The FABER test has limited diagnostic utility despite being the only clinical test cautiously recommended for screening hip-related pain 1
• Interrater reliability is moderate (kappa 0.63) with fair agreement levels 6
• The test has good sensitivity but poor specificity, meaning it screens well but doesn't confirm specific diagnoses 1

Diagnostic Accuracy Concerns

• A positive FABER test alone has very limited ability to confirm FAI syndrome by increasing post-test probability 1
• Limited to substantial ability to help confirm acetabular dysplasia/hip instability in low-quality studies 1
• Other clinical special tests (Thomas test, prone instability test) are not recommended due to insufficient evidence for ruling hip disease in or out 1

Clinical Context Requirements

• Hip arthroscopy remains the definitive diagnostic procedure for intra-articular pathology when clinical suspicion is high despite negative imaging 3
• A negative MRI should not preclude arthroscopy if there is high clinical suspicion, as MRI has relatively high false-negative rates despite 100% specificity 3
• The diagnostic approach must be comprehensive and contextual, integrating clinical expertise with evidence-based practice 1