Trendelenburg gait

Pathophysiology: The gluteus medius and minimus, innervated by the superior gluteal nerve (L4-S1), stabilize the pelvis during single-leg stance by contracting on the weight-bearing side to prevent the contralateral hip from dropping. When these muscles are weak or denervated, the pelvis drops on the side opposite the affected hip during the stance phase (positive Trendelenburg sign), and patients compensate by leaning their trunk toward the affected (weak) side to shift the center of gravity, producing a characteristic waddling gait when walking.

Etiologies: Superior gluteal nerve injury (classic causes include iatrogenic injury during hip surgery, especially total hip arthroplasty via the anterolateral/Hardinge approach, or intramuscular injections given too medially in the upper outer quadrant of the buttock), L5 radiculopathy, polio, muscular dystrophy (e.g., Duchenne), hip dysplasia, and avascular necrosis of the femoral head.

Clinical testing: The Trendelenburg test is performed by having the patient stand on one leg; a positive test shows the pelvis dropping on the side of the raised (unsupported) leg, indicating weakness of the hip abductors on the side of the leg bearing weight (the standing leg). Importantly, the test identifies weakness on the side of the stance leg, not the side where the pelvis drops.

Clinical significance: Important for localizing superior gluteal nerve lesions and differentiating from other causes of gait abnormality (e.g., antalgic gait, foot drop, ataxic gait). High-yield for both anatomy (superior gluteal nerve course through greater sciatic foramen below piriformis) and surgical complications of hip procedures.