Trendelenburg's sign
A sign of hip abductor weakness causing pelvic drop on the swing side.
Trendelenburg's sign is a clinical finding associated with weakness or paralysis of the hip abductor muscles, specifically the gluteus medius and gluteus minimus. It is named after the German surgeon Friedrich Trendelenburg. The sign is often confused with the Trendelenburg test, which evaluates vascular insufficiency in the lower extremities.
Quick Facts
- Differential
- paralyzed abductor muscles
Facts from the source article.
Signs and symptoms
The Trendelenburg sign is considered positive when, during single-leg stance on the affected side, the pelvis drops markedly on the opposite side. This drop occurs because the abductor muscles of the stance leg are weak. Some patients compensate by tilting the trunk toward the affected side, which raises the pelvis on the opposite side instead. Whether the pelvis drops or rises depends on whether compensation is present. Compensation shifts the center of gravity toward the affected side and reduces the angle between the hip adductors and femur, lowering the force required from the adductors to maintain posture. The gluteus medius is crucial during the stance phase of gait, which accounts for about 60% of the gait cycle. During this phase, roughly three times body weight is transmitted to the hip joint, with the hip abductors handling two-thirds of that load. A positive sign may arise from muscular dysfunction, such as weakness of the gluteus medius or minimus, or from pain.
Causes
A positive Trendelenburg sign results from weakness or ineffective action of the gluteus medius and gluteus minimus. Causes include damage to the superior gluteal nerve, polio involving L5 (which may also cause foot drop), tendinitis, penetrating injury, infection (blood-borne, post-traumatic, or post-surgical), and temporary or permanent weakness of the lateral glutei. Ineffective leverage of these muscles can occur due to greater trochanteric avulsion, femoral neck fracture or non-union, coxa vara (femoral neck-shaft angle less than 120 degrees), or hip joint damage such as chronic or developmental hip dislocation, dysplasia, osteonecrosis, Legg-Calve-Perthes disease, or uncorrected traumatic dislocation.
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