biology

Trendelenburg's sign

Trendelenburg's sign is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Trendelenburg's sign rather than just read about it. In short: Trendelenburg's sign is found in people with weak or paralyzed abductor muscles of the hip, namely gluteus medius and gluteus minimus. It is named after the German surgeon Friedrich Trendelenburg.

Key takeaways

Trendelenburg's sign belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Trendelenburg's sign to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Trendelenburg's sign from memory before moving on to harder problems.

Reference excerpt

Trendelenburg's sign is found in people with weak or paralyzed abductor muscles of the hip, namely gluteus medius and gluteus minimus. It is named after the German surgeon Friedrich Trendelenburg. It is often incorrectly referenced as the Trendelenburg test which is a test for vascular insufficiency in the lower extremities.

Signs and symptoms The Trendelenburg sign is said to be positive if, when standing on one leg (the 'stance leg'), the pelvis severely drops on the side opposite to the stance leg (the 'swing limb'). The muscle weakness is present on the side of the stance leg. If the patient compensates for this weakness by tilting their trunk/thorax to the affected side, then the pelvis will be raised, rather than dropped, on the side opposite to the stance leg. Ergo, in the same situation, the patient's hip may be dropped or raised, dependent upon whether the patient is actively compensating or not. Compensation shifts the center of gravity to the affected side, and also decreases the angle between the hip adductor muscles and femur, both of which decrease the forces needing to be applied by the hip adductor muscles to maintain relevant posture. The gluteus medius is very important during the stance phase of the gait cycle to maintain both hips at the same level. One leg stance accounts for about 60% of the gait cycle, and during the stance phase, there is approximately three times the body weight transmitted to the hip joint. The hip abductors' action accounts for two thirds of that body weight. A Trendelenburg sign can occur when there is presence of a muscular dysfunction (weakness of the gluteus medius or minimus) or when someone is experiencing pain.

Causes A positive Trendelenburg's sign is caused by weakness or ineffective action of the abductor muscles of the lower limb, the gluteus medius muscle and the gluteus minimus muscle.

Damage to the motor nerve supply of the lateral gluteal muscles (gluteus medius muscle and gluteus minimus muscle) Polio involving L5 (foot drop may also be seen because L5 innervates the tibialis anterior muscle). Damage to the superior gluteal nerve. Temporary or permanent weakness of the lateral glutei Tendinitis. Penetrating injury. Infection, abscess – blood borne, post-traumatic or post-surgical. Ineffective action (insufficient leverage) of the lateral glutei Greater trochanteric avulsion. Fracture, (or non-union) of the femoral neck. Coxa vara (the angle between the femoral neck head and shaft is less than 120 degrees). Damage to the hip joint (fulcrum) - Chronic or Developmental Hip Dislocation/Dysplasia Osteonecrosis. Legg-Calve-Perthes disease. Developmental dysplasia. Chronic infection. Uncorrected traumatic dislocation.

See also Gait abnormality Superior gluteal nerve Trendelenburg gait

References

External links Trendelenburg Test at GPNotebook

Illustrations

Worked examples

Example 1 — a first encounter with Trendelenburg's sign

Start with the simplest possible case. Write down what Trendelenburg's sign claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Trendelenburg's sign before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Trendelenburg's sign ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Trendelenburg's sign

In research: Trendelenburg's sign appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Trendelenburg's sign in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Trendelenburg's sign is common in secondary-school and first-year university syllabi. It links to neighbouring topics Athletic training, Eponyms in medicine, Medical sign stubs, so understanding it makes those chapters shorter.
In everyday life: Look for Trendelenburg's sign outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Trendelenburg's sign in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Trendelenburg's sign means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Trendelenburg's sign out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Trendelenburg's sign in simple terms?

Trendelenburg's sign is found in people with weak or paralyzed abductor muscles of the hip, namely gluteus medius and gluteus minimus. It is named after the German surgeon Friedrich Trendelenburg.

Why does Trendelenburg's sign matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Trendelenburg's sign?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Trendelenburg's sign.