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The aim of the Trendelenburg’stest is to assess the strength of the hip abductors, specifically the gluteus medius and minimus.1
The test is named after FriedrichTrendelenburg, who described the test in 1895.
Hip abductors assessed in Trendelenburg’s test 2
The hip abductors which are assessed with Trendelenburg’s test are shown in the table below.
Gluteal surface of the ilium
Greater trochanter of the femur
All fibres: abduct the hip
Anterior fibres: flex and medially rotate the hip
Posterior fibres: extend and laterally rotate the hip
Superior gluteal nerve
Gluteal surface of the ilium
Greater trochanter of the femur
Abduct, medially rotate and flex the hip
Superior gluteal nerve
Gait cycle in brief
The gait cycle is the sequence of events between the time one foot touches the ground and the time the same foot returns to the same position. Events of the gait cycle include heel strike; foot flat; push off (heel off + toe-off) and the stance and swing phases.1
During the foot flat phase of the gait cycle, the contralateral leg is lifted to do the heel strike. While the contralateral leg is in the air and the ipsilateral leg is on the floor (mid-stance/single leg stance), the position of the hip during this stage is important to observe when assessing the strength of the hip abductors (because all the weight of the body is being borne on one leg).
If the hip abductors aren’t strong enough, or there’s pain inhibition, the patient can’t counterbalance the weight of the upper body on the affected limb. As a result, the pelvis will sag towards the floor while standing on the affected limb, as opposed to being lifted.
When would you perform Trendelenburg’s test?
When a patient complains of a limp, or hip pain or as part of a normal physical examination assessing gait.
If the patient is comfortable to stand alone, stand behind the patient. Alternatively stand in front of the patient, with their forearms positioned on yours to support them.
Ask the patient to lift each foot in turn off the ground.
When the patient lifts their right foot, the left hip abductors are being tested.
When the patient lifts their left foot, the right hip abductors are being tested.
Position your hands on the patient’s iliac crests (make sure to clearly explain each of the steps and gain consent prior to doing this).
Observe carefully if the hip on the unsupported side lifts or droops.
If the patient is using your arms for support, you will feel them pressing down on one of your arms if their hip abductors are unable to support their weight.
Abductors should be sufficiently strong to keep the pelvis level during a single leg stance, but it is normal to see a slight elevation of the pelvis on the unsupported site (this is due to the abductor muscles contracting – see Figure 1).3
A positive Trendelenburg’s sign (pathological) involves sagging of the pelvis on the unsupported side due to the abductor muscles failing to stabilise the hip towards the weight-bearing femur (see Figure 2).
Trendelenburg’s gait involves excessive up-down motion of the pelvis whilst walking.
It occurs as a result of compensatory mechanisms due to the drooping pelvis.3
Unilateral positive Trendelenburg’s sign produces a lurchinggait.
Bilaterally positive Trendelenburg’s sign produces a waddlinggait.
Imagine a chair…when you remove a leg what happens? The chair will normally fall towards the side that had the leg removed. The human body is the same, the centre of gravity passes midway through the body and through the pubic symphysis.
When standing on one leg, the centre of gravity, much like the chair, shifts to the unsupported leg.
We don’t fall because the hip abductors pull the pelvis towards the femur of the weight-bearing leg.
Lever mechanics of the hip joint
The operation of most skeletal muscles involves leverage – using a lever to move an object.
A lever is a rigidbar that moves on a fixedpoint called the fulcrum when a force is applied to it.
In the human body, the joints are fulcrums, and the bones act as levers.
Forces can be exerted across levers in the form of load and effort.
Musclecontraction provides the effort that is applied at the muscle’s insertion point on the bone.
The load is the bone itself, along with the overlying tissues.
There are 3 types of levers and they differ depending on where the fulcrum, load and effort are positioned relative to each other.6
The hip, in this case, is a class 3 lever. This means that the effort (force exerted by hip abductors) is positionedbetween the fulcrum (hip joint) and the load (upper body weight), acrossa lever (the neck of the femur) – see Figure 3.
In order to keep the structure absolutely level, the forces of effort and load applied across their distances from the fulcrum must be balanced and cancel each other out (Figure 4).
Applying this to the hip joint (Figure 5), as the distance between the hip joint and the hip abductors is half of the distance between the hip joint and the centre of gravity (pubic symphysis), it so follows that the effort exerted by the hip abductors must be twice the force exerted by the upper body weight.
Causes of Trendelenburg’s sign
Any problems that affect the hip can cause a positive Trendelenburg’ssign (Figure 6). As upper body weight cannot be changed or affected, this leaves conditions affecting the hip joint or femur (skeletalabnormalities) and hip abductors (neuromuscularabnormalities).8
Examples of skeletal abnormalities which can result in Trendelenburg’s sign:7,8,9
Developmental dysplasia of the hip (DDH) – a spectrum of disorders that cause spontaneous dislocation of the hip
Coxa vara – the angle between the femoral neck and femoral shaft is less than 120°
Slipped capital femoral epiphysis (SCFE) – the femoral metaphysis slides in relation to the epiphysis
Legg-Calve-Perthes disease – a childhood hip disorder marked by femoral head necrosis
Chronic subluxation/dislocation of the hip – resulting in hip instability
Greater trochanter fracture (acute or non-united) – insertion of the gluteus medius and minimus are compromised
Examples of neuromuscular abnormalities which can result in Trendelenburg’s sign:7,8,9
Superior gluteal nerve injury – often iatrogenic following total hip replacement/hemiarthroplasty or due to trauma
L5 radiculopathy – the superior gluteal nerve is formed from L4, L5 and S1 spinal roots; often accompanied by foot drop
Gluteus medius and minimus weakness or damage (e.g. tears or tendonitis)
Poliomyelitis – causing paralysis of the hip abductors
Muscular dystrophy and other neuromuscular disorders
Pain inhibition leading to gluteal weakness (e.g. osteoarthritis of the hip)
Limitations of the test
A positive Trendelenburg’s sign may be concealed in early stages of osteonecrosis and pelvic drop can occur in healthy individuals with normalhipabductormechanism but inadequatefunction.8
Falsepositives can occur with lack of understanding/compliance, significant hip pain, and scoliosis (the costal margin may impinge on the iliac crest).
Falsenegatives may occur when patients compensate by shifting their torso (and centre of gravity) over the weight-bearing hip, so be vigilant for upper body movements.9
The goal is to identify the underlying cause of the abnormal gait. A thorough history and clinical examination are essential before further investigations are considered.
X-ray of the local joints (e.g. knee, hip, lumbar spine)
Consider ultrasound, CT or MRI
Baseline blood tests may be performed to screen for evidence of system diseases (e.g. inflammatory arthropathies)
Nerve conduction studies
It is useful to be able to differentiate Trendelenburg gait from other common gait patternsincluding:3,4
Antalgic gait: occurs due to pain upon weight-bearing, causing the patient to only briefly step on the painful side
Short-leg gait: caused by a discrepancy in length between the two legs; a consistent dip of the pelvis on the shorter side is observed
Trendelenburg’s test assesses the strength of the hipabductors.
It is performed as part of a routinegaitexamination or when a patient complains of a limp or hippain.
A positive Trendelenburg’s sign (pathological) involves sagging of the pelvis on the unsupported side due to the abductor muscles failing to stabilise the hip towards the weight-bearing femur.
If a positive sign is present, Trendelenburg’s gait may also be observed.
Causes of a positive Trendelenburg’s sign include skeletal and neuromuscularabnormalities affecting the hip and hip abductors respectively.
Trendelenburg’s gait should be differentiated from antalgicgait (due to pain) and short-leg gait (due to differences in leg length).
Miss Margaret Brooks
University Hospitals of Birmingham NHS Foundation Trust
The Orthopaedic Physical Examination 2nd ed, Elsevier, 2005
Trail Guide to the Body 3rd ed, Books of Discovery, 2005
Hamblen and Simpson. Adams’s Outline of Orthopaedics 14th ed, Churchill Livingstone Elsevier, 2010
Solomon, Warwick and Nayagam. Apley and Solomon’s Concise System of Orthopaedics and Trauma, 4thed, Taylor & Francis Group, 2014
Duckworth and Blundell. Lecture Notes: Orthopaedics and Fractures 4th ed, Wiley-Blackwell, 2010
Marieb and Hoehn. Human Anatomy and Physiology, 7th ed, Benjamin Cummings, 2011
Azar, Beaty and Canale. Campbell’s Operative Orthopaedics13th ed, Elsevier, .2017
Gandbhir VN, Rayi A. Trendelenburg Gait, StatPearls Publishing; 2020 Jan – [NCBI]
Hardcastle and Nade. The Significance of the Trendelenburg Test (JBJS Br, 67-B no 5. 1985)
Figure 1 and 2: Illustrated by Leyla Noury, Sketchbook, 2020
Figures 3 to 6: Illustrated by Leyla Noury, Paint, 2020