What is the Trendelenburg sign?

What is the Trendelenburg Sign?

The Trendelenburg sign is a clinical test used to assess hip abductor muscle function, specifically the gluteus medius and minimus muscles, where a positive test indicates weakness or dysfunction of these muscles when the patient stands on one leg and the pelvis drops on the contralateral (non-stance) side. 1

Clinical Performance of the Test

The test is performed by asking the patient to stand on one leg for approximately 30 seconds while the examiner observes the position of the pelvis and trunk in the coronal plane 2:

• Patient stands on the affected limb while lifting the opposite leg off the ground 1
• Normal response (negative test): The pelvis on the non-stance side remains level or elevates slightly 1
• Abnormal response (positive test): The pelvis drops on the non-stance side, indicating weakness of the hip abductors on the stance side 1, 2

Biomechanical Criteria and Measurement

Objective assessment requires evaluation of both pelvic tilt angle and trunk alignment, with specific kinematic cutoffs established through motion analysis 2:

• Baseline pelvic-on-femoral (P-O-F) position averages 83° ± 3° in healthy individuals 3
• A change of at least 4° in P-O-F position represents a meaningful clinical change beyond measurement error 3
• Hip abductor muscle activity increases when the pelvis is elevated and decreases when it drops during single-leg stance 4

Clinical Application in Hip Pathology

The Trendelenburg sign is used to identify hip abductor tendon pathology, particularly after total hip arthroplasty 5:

• In post-THA patients with positive Trendelenburg signs, ultrasound detected abductor tendon tears in 50% of cases (4 of 8 patients) 5
• Patients with negative Trendelenburg tests had tears in only 12% of cases (3 of 26 patients) 5
• Abductor muscle weakness or detachment commonly occurs after THA using an anterolateral approach 5

Important Pitfalls and Limitations

Several factors can produce false-positive or false-negative results 1:

False-Positive Results:

• Pain limiting patient effort 1
• Lack of patient cooperation 1
• Impingement between rib cage and iliac crest 1

False-Negative Results:

• Compensatory trunk lean toward the stance side 1, 4
• Use of muscles above and below the pelvis for compensation 1
• Patient leaning beyond the hip on the standing side 1

Diagnostic Accuracy

The Trendelenburg test has limited sensitivity for early hip joint osteoarthritis 6:

• Sensitivity for identifying hip OA: 0.55 6
• Specificity: 0.70 6
• Positive likelihood ratio: 1.83 6
• The test is not useful for identifying subjects in early stages of hip joint OA 6

Modified Testing Methodology

To improve reliability, the test should be performed with minimum trunk sway and severe flexion on the non-test side 4:

• Assessment should focus on whether the patient can maintain single-leg stance when forced to elevate the pelvis, not simply on pelvic drop 4
• The test requires standardized evaluation of both pelvis and trunk coronal plane alignment during the 30-second stance period 2