🦵 Understanding the Trendelenburg Sign (Normal vs Positive)

The Trendelenburg sign is a classic orthopedic and neurologic clinical test used to evaluate hip abductor muscle function, especially the gluteus medius and gluteus minimus. It plays an important role in diagnosing conditions that affect hip stability and identifying causes of abnormal gait patterns.

This sign is especially valuable because weakness of hip abductors is linked to hip joint disease, nerve injury, muscle disorders, and structural abnormalities.

✅ What Is the Trendelenburg Sign?

The Trendelenburg sign is assessed by asking a person to stand on one leg.

Normal Response

When standing on one leg, the pelvis remains level or slightly rises on the lifted-leg side.
This happens because the hip abductors on the standing leg contract to maintain pelvic stability.

Positive Trendelenburg Sign

A positive sign occurs when the pelvis drops on the opposite (contralateral) side of the lifted leg.
This indicates weakness or dysfunction of the hip abductors on the stance leg.

🧠 Why Does a Positive Trendelenburg Sign Happen?

The hip abductors act like “pelvic stabilizers.” When one foot is lifted, these muscles contract to prevent the pelvis from falling.

If the abductors are weak or nerve supply is impaired:

✅ The pelvis drops on the opposite side
✅ The trunk leans toward the affected side
✅ A Trendelenburg gait may appear during walking

🚶 Trendelenburg Gait (Compensatory Lean)

Many people compensate for hip abductor weakness by leaning their torso toward the weak side.

This reduces the load on the abductors and helps them stay upright—but creates a visible limp.

📋 Trendelenburg Sign Summary Table

Feature	Normal Trendelenburg	Positive Trendelenburg
Pelvic alignment	Pelvis stays level	Pelvis drops on opposite side
Hip abductor strength	Normal	Weak on the stance leg
Trunk position	Upright	Trunk leans toward affected leg
Gait impact	Normal walking pattern	Trendelenburg gait (limping)
Clinical meaning	Stable hip abductors	Suggests hip/nerve/muscle problem

📌 Common Causes of a Positive Trendelenburg Sign

A positive Trendelenburg sign may result from:

✅ 1. Hip Abductor Weakness

• Gluteus medius/minimus injury

• Muscle atrophy

• Prolonged inactivity

✅ 2. Superior Gluteal Nerve Damage

• Trauma or surgery

• Incorrect IM injections

• L5 radiculopathy

✅ 3. Hip Joint Pathology

• Osteoarthritis of the hip

• Hip dysplasia

• Femoral neck fracture

• Legg-Calvé-Perthes disease

✅ 4. Structural Abnormalities

• Congenital hip deformities

• Limb length discrepancy

🩺 How to Perform the Trendelenburg Test

1. Ask the patient to stand upright

2. Have them lift one leg (knee bent)

3. Observe the pelvis for 10–30 seconds

✅ Normal: pelvis remains level
❌ Positive: pelvis drops on lifted-leg side

⭐ Why It Matters Clinically

Trendelenburg testing helps clinicians evaluate:

✅ Hip stability
✅ Neuromuscular integrity
✅ Causes of limping
✅ Rehab progress after injury or surgery

✅ Key Takeaway

A positive Trendelenburg sign indicates weakness of hip abductors on the standing leg and causes:

• Contralateral pelvic drop

• Trunk lean toward affected side

• Limping (Trendelenburg gait)

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