CAN TRENDELENBURG’S SIGN BE POSITIVE IF THE HIP IS
NORMAL?
P. N. VASUDEVAN,
K. V. VAIDYALINGAM,
P. BHASKARAN NAIR
From the R. V. Institute of Research in Ilizarov Technology, Kerala, India
In 1895 Trendelenburg described his sign to determine
the integrity of hip function. We found the sign to be
positive in a patient whose hip was clinically and
radiologically normal, and therefore investigated this in
other patients. We confirmed that a medial shift of the
mechanical axis of the leg below the hip may cause a
positive Trendelenburg sign. This has not been
previously described.
J Bone Joint Surg [Br] 1997;79-B:462-6.
Received 9 December 1996; Accepted 11 February 1997
In 1895 Freidrich Trendelenburg described a clinical sign
useful for determining the integrity of the function of hip
abductor muscles, with specific reference to congenital
1
dislocation of the hip and progressive muscular atrophy.
His report appeared when physicians had few aids to
diagnosis: clinical radiography was not yet available, since
2
Roentgen had discovered X-rays only two years earlier.
Most orthopaedic and physiotherapy textbooks describe
the Trendelenburg sign as a diagnostic test of function and
3
dysfunction of the hip. Apley’s System of orthopaedics
gives the following description: “Normally each leg bears
half the body weight. When one leg is lifted the other takes
the entire weight. As a result the trunk has to incline
towards the weight-bearing leg. This is achieved by the hip
abductors; their insertion is fixed and the pull is exerted on
their origin. Consequently the pelvis tilts, rising on the side
not taking weight. When this mechanism fails Trendelenburg’s sign is positive. The pelvis drops instead of rising on
the unsupported side” (Fig. 1).
The Trendelenburg sign becomes positive when there is
abductor weakness, as in poliomyelitis or muscular dystrophies. It is also positive in coxa vara when there is insuffi-
cient room for abduction and the trochanter meets the
3
pelvic wall before the pelvis can tilt sufficiently if the hip
is dislocated and there is no stable fulcrum, and if the
femoral neck is fractured so that the lever system is
destroyed.
We had reason to re-examine the mechanism of the
Trendelenburg sign when a 65-year-old man came to us
with a middle-third tibial fracture malunited for ten years in
37° varus. His complaints were deformity and a limp,
occasionally with knee pain. He was found to have a
Trendelenburg gait but none of the causes listed above
could be confirmed. We disregarded the sign and corrected
his tibial deformity. After this realignment of the tibia we
were surprised that the Trendelenburg gait had disappeared.
We therefore studied similar cases to determine the real
mechanism of a Trendelenburg gait in a patient with normal
hips.
PATIENTS AND METHODS
We selected 17 patients and studied 23 legs. All the patients
had an acquired Trendelenburg gait (Fig. 2). None had
fixed scoliosis, fixed pelvic obliquity, obvious pathology of
the hip, muscle weakness due to poliomyelitis or dystrophy,
any painful conditions which prevented standing on the leg,
P. N. Vasudevan, MS Ortho, DNB Ortho, Senior Orthopaedic Surgeon
K. V. Vaidyalingam, MS Ortho, Senior Orthopaedic Consultant
P. Bhaskaran Nair, MS Ortho, Senior Orthopaedic Consultant and former
Director and Professor of Orthopaedics
R. V. Institute of Research in Ilizarov Technology, R. V. Clinic, West Fort
Road, Palakkad 678 001, Kerala, India.
Correspondence should be sent to Dr P. N. Vasudevan.
©1997 British Editorial Society of Bone and Joint Surgery
0301-620X/97/37495 $2.00
462
Fig. 1
Diagram showing the lever system which acts in abduction of the
hip.
THE JOURNAL OF BONE AND JOINT SURGERY
CAN TRENDELENBURG’S SIGN BE POSITIVE IF THE HIP IS NORMAL?
463
Fig. 3
Tracing from a monopodal weight-bearing radiograph of a patient
with varus deformity of the right knee standing on the right leg and
demonstrating a positive Trendelenburg sign.
Fig. 4
Diagram showing the mechanical
axis of the lower limb and its passage through the tibial spine in a
normal limb.
Fig. 2
Gross varus deformity of both knees, a cause of the
Trendelenburg gait.
or altered function of the hip abductor muscles. Clinical
and radiological examination confirmed this normality and
hip abductor power was MRC grade 5 in all cases. Deformity of the leg was assessed by full-length standing radiographs from hip to heel. Monopodal weight-bearing
radiographs of the pelvis (Fig. 3) were taken if the leg
deformity was only diaphyseal, and full leg-length films if
the deformity was juxta-articular to evaluate its magnitude
when bearing weight.
Definition of mechanical axis. The mechanical axis of the
limb was taken to be a line connecting the centre of the
femoral head to the centre of the ankle mortice. Normally,
this passes through the tibial spine of the knee. We defined
medial or lateral shift of the measured line as medial or
4-7
lateral deviation of the mechanical axis of the limb.
In a normal limb, a line from the centre of the femoral
head to the tip of the greater trochanter (hip orientation
line) is usually at about 90° to the mechanical axis (Fig. 4),
and in the tibia, the mechanical and anatomical axes are the
same. In the femur, the mechanical axis is from the centre
of the femoral head to the centre of the knee, and the
anatomical axis is from the piriformis fossa to the centre of
VOL. 79-B, NO. 3, MAY 1997
4-7
the knee. The two lines subtend about 6° to each other, :
the anatomical axis of the femur at the hip is in 6° of
adduction during normal walking.
RESULTS
Of the 17 patients whom we studied (23 limbs), three had
bowing deformity of both lower limbs (Fig. 5), four had
malunited fractures of the femoral shaft, five had osteoarthritis of the knee with varus deformity (Fig. 2), four had
diaphyseal tibia vara and one had Blount’s disease.
For the planning of surgical correction the magnitude,
464
P. N. VASUDEVAN,
K. V. VAIDYALINGAM,
P. BHASKARAN NAIR
Fig. 6
Diagram showing the relationship of the centre of the femoral head
to the tip of the greater trochanter in adduction and abduction.
Fig. 5
Tracing of a radiograph of the legs of a patient with gross femoral bowing
and proposed osteotomies for correction. By re-establishing the mechanical axis the Trendelenburg sign was abolished.
level and plane of the deformity were assessed by the
4-7
methods described by Paley. In bowing deformities the
angle of the hip orientation line to the ankle mortice was
recorded (measured as Cobb method of scoliosis) as a gross
assessment. All of the patients had medial deviation of the
mechanical axis at the knee with or without ligamentous
laxity.
DISCUSSION
The main plane of knee and ankle movement is in flexion
and extension around a coronal axis. If the axis of fracture
malunion is in the coronal plane these joints and the hip can
compensate so that the gait looks normal. The hip is the
only joint in the lower limb which allows much adduction
and abduction and therefore any varus or valgus deformity
of the leg can be compensated for only at the hip, and to a
minimal extent at the subtalar joints. Any varus or valgus
deformity between the hip and ankle must therefore influence hip mechanics. Varus deformity of the femur, knee, or
tibia requires the hip to adopt an abducted position (valgus
angulation) to maintain a straight mechanical axis of the
limb in walking. The mechanics of hip abduction act as a
type-III lever, with its fulcrum at the centre of the femoral
head: the abductor muscles are inserted below the tip of the
greater trochanter (Fig. 1). When the centre of the head and
the tip of the trochanter are in the same plane, parallel to
the floor, then the insertion is distal to the fulcrum.
If the hip is abducted in compensation for a varus
deformity below the hip, the trochanter rotates proximally
in the coronal plane so that it is above the fulcrum (Fig. 6),
Fig. 7
Diagram showing the ineffective function of normal abductor
muscles when the femur is placed in an abducted position as a
consequence of varus deformity of the limb.
thus effectively shortening and weakening the abductor
muscles. The angle between the hip orientation line and the
mechanical axis of a varus limb will exceed 90° and the 6°
adducted position of the femur in normal walking is lost.
This affects the strength that can be generated by the
abductor muscles although they are normal (Fig. 7).
Depending on the amount of compensation, these patients
will have either a normal gait, a delayed Trendelenburg
2
sign or a Trendelenburg gait. Medial deviation of the
mechanical axis is thus another cause of a Trendelenburg
gait or sign.
We suggest that the Trendelenburg sign should now be
classified as having three possible mechanisms:
THE JOURNAL OF BONE AND JOINT SURGERY
CAN TRENDELENBURG’S SIGN BE POSITIVE IF THE HIP IS NORMAL?
465
Fig. 9
Fig. 8
This girl has Blount’s disease resulting in a positive
Trendelenburg sign. The cause is infrapelvic and the
medial border of the thigh therefore appears to be
abducted.
This man has a classical Trendelenburg sign due to
CDH. Note that the medial border of the thigh is
adducted.
2
1) Suprapelvic. Costopelvic impingement as in scoliosis.
2) Pelvic. This is due to loss of the fulcrum as in developmental dysplasia of the hip; or of the lever mechanism as
in nonunion of the femoral neck; or of power as in poliomyelitis or muscular dystrophy.
3) Infrapelvic. This is caused by medial deviation of the
mechanical axis of the lower limb.
The positive Trendelenburg sign due to infrapelvic causes can be easily differentiated from that due to classical
causes. During normal monopodal weight-bearing the
medial border of the thigh, which is roughly parallel to the
mechanical axis of the femur, is perpendicular. In patients
with pelvic causes of a positive Trendelenburg sign the
thigh is orientated obliquely and inwards (adducted at the
hip) (Fig. 8).
VOL. 79-B, NO. 3, MAY 1997
In patients with a positive Trendelenburg sign due to
infrapelvic causes the medial border of the thigh proximal
to the site of a varus deformity, is orientated obliquely and
outwards, that is, abducted at the hip (Fig. 9). The part of
the limb distal to the deformity is orientated obliquely and
inwards. In patients with proximal varus deformity of the
femur or coxa vara this clinical sign is difficult to assess
because of the bulkiness of the thigh and proximity to the
hip. Such patients will appear to have a classical Trendelenburg sign because only that part of the limb distal to the
varus deformity can be observed.
No benefits in any form have been received or will be received from a
commercial party related directly or indirectly to the subject of this
article.
466
P. N. VASUDEVAN,
K. V. VAIDYALINGAM,
P. BHASKARAN NAIR
REFERENCES
1. Trendelenburg F. Dtsch Med Wochenschr 1895;21:21.
2. Nade PH-S. The significance of Trendelenburg test. J Bone Joint Surg
1985;67-B:5:741-6.
3. Apley G. Apley’s system of orthopaedics and fractures. 6th edition,
ELBS, 1986:243.
4. Paley D. Tetsworth KD. Operative orthopaedics, II Edition. In: Chapman WW, ed. Deformity correction by the Ilizarov technique. JB
Lippincot & Co, 1993:883.
5. Paley D, et al. Deformity planning for frontal and sagittal plane
corrective osteotomies. OCNA 1994;Vol. 25 No. 3.
6. Paley D, Tetsworth K. Mechanical axis deviation of the lower limbs:
preoperative planning of uniapical angular deformities of the tibia and
femur. Clin Orthop 1992;280:48-64.
7. Paley D, Tetsworth K. Mechanical axis deviation of lower limb,
preoperative planning of multiapical frontal plane angular and bowing
deformities of femur and tibia. CORR 1992;280:65.
THE JOURNAL OF BONE AND JOINT SURGERY