Trendelenburg Test

What It Tests

The Trendelenburg test assesses the strength and integrity of the hip abductor mechanism - primarily the gluteus medius and gluteus minimus muscles, acting on a stable fulcrum between the pelvis and femur.

How to Perform

Ask the patient to stand on the unaffected limb first - the buttock on the affected side automatically rises (normal).
Ask the patient to stand on the affected limb - watch the pelvis from behind.
Observe the iliac crests and gluteal folds for any drop.

The examiner should stand behind the patient to best visualize pelvic tilt.

Interpreting the Result

Finding	Interpretation
Normal (negative): Standing on one leg causes pelvis to rise on the opposite (swing) side	Abductors functioning normally
Positive: Pelvis drops/sags on the unsupported (swing) side	Abductor mechanism failure on the stance side

Remember the mnemonic: the pelvis drops away from (opposite to) the weak side.

Clinical Photos

Left panel: standing on normal (N) leg - pelvis on diseased (D) side rises normally. Right panel: standing on diseased (D) leg - pelvis drops on normal (N) side = positive test.

Trendelenburg test - diagrammatic representation showing pelvic tilt

Diagrammatic cross-section showing pelvic tilt in the two positions - D = diseased side, N = normal side.

Causes of a Positive Trendelenburg Sign

The test reflects failure of the osseomuscular mechanism between pelvis and femur. It becomes positive in four broad categories:

Weak abductors - poliomyelitis, muscular dystrophies, motor neurone disease, superior gluteal nerve damage
Unstable fulcrum - congenital or pathological dislocation of the hip (muscles cannot act without a stable pivot)
Broken lever system - fracture neck of femur, coxa vara, Perthes' disease
Pain inhibition - any arthritis of the hip causing the patient to avoid loading the affected side

Nerve Involved

A positive sign most commonly reflects damage to the superior gluteal nerve (L4, L5, S1), which supplies gluteus medius, gluteus minimus, and tensor fasciae latae. Causes include:

Pelvic fractures
Space-occupying lesions in the greater sciatic foramen
Hip surgery with disruption/atrophy of the gluteus medius/minimus tendon insertion on the greater trochanter

Gait Consequence: The Duchenne Limp / Waddling Gait

When the abductors fail, the pelvis drops toward the swing side during the stance phase. The patient compensates by lurching the trunk toward the affected side (Duchenne limp) - this shifts the centre of gravity over the stance limb and reduces the pelvic drop. With bilateral small gluteal weakness, this produces a characteristic waddling gait.

Unilateral weakness = Trendelenburg sign + Duchenne limp
Bilateral weakness = waddling (gluteal) gait

Brodie-Trendelenburg Test (Vascular - Different Test)

Note there is also a separate Brodie-Trendelenburg test used in vascular surgery to assess sapheno-femoral valve incompetence in varicose veins. The leg is elevated to drain varicosities, a tourniquet is applied at the suspected incompetent feeding vein, and the patient stands. If varices remain empty with the tourniquet in place but fill immediately on release, the site of incompetence has been correctly identified. This is an entirely different test despite sharing the Trendelenburg name.

Sources: S Das - A Manual on Clinical Surgery 13th Ed, p. 240 | Gray's Anatomy for Students | THIEME Atlas of Anatomy - General Anatomy and Musculoskeletal System | Pye's Surgical Handicraft 22nd Ed | Gray's Anatomy for Students

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