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358 THE JOURNAL OF BONE AND JOINT SURGERY
M. Beck, MD
C. F. Dora, MD
R Ganz, MD
Clinic of Orthopaedic Surgery, University of Berne, Inselspital, 3010
Berne, Switzerland.
E. Gautier, MD
Department of Orthopaedic Surgery, Hôpital Cantonal, 1708 Fribourg,
Switzerland.
J. B. Sledge, MD
Department of Orthopaedics, Boston Medical Centre, 818 Harrison Ave-
nue, Dowling, 2 North Boston, Massachusetts 02188, USA.
Correspondence should be sent to Dr M. Beck.
©2000 British Editorial Society of Bone and Joint Surgery
0301-620X/00/310356 $2.00
The anatomy and function of the gluteus
minimus muscle
Martin Beck, John B. Sledge, Emmanuel Gautier, Claudio F. Dora,
Reinhold Ganz
From the University of Berne, Switzerland
I
n order to investigate the functional anatomy of
gluteus minimus we dissected 16 hips in fresh
cadavers. The muscle originates from the external
aspect of the ilium, between the anterior and inferior
gluteal lines, and also at the sciatic notch from the
inside of the pelvis where it protects the superior
gluteal nerve and artery. It inserts anterosuperiorly
into the capsule of the hip and continues to its main
insertion on the greater trochanter.
Based on these anatomical findings, a model was
developed using plastic bones. A study of its
mechanics showed that gluteus minimus acts as a
flexor, an abductor and an internal or external rotator,
depending on the position of the femur and which
part of the muscle is active. It follows that one of its
functions is to stabilise the head of the femur in the
acetabulum by tightening the capsule and applying
pressure on the head. Careful preservation or
reattachment of the tendon of gluteus minimus during
surgery on the hip is strongly recommended.
J Bone Joint Surg [Br] 2000;82-B:358-63.
Received 12 July 1999; Accepted after revision 18 August 1999
Knowledge of the anatomical relationships and function of
gluteus minimus is limited. It is described as a fan-shaped
muscle arising from the external iliac fossa between the
anterior and inferior gluteal lines and covered almost
entirely by gluteus medius.
1-5
Reports of the exact site of
the insertion of the tendon of gluteus minimus vary. Some
describe it as at the anterior surface of the greater trochan-
ter,
2,3
and some to the external side of the anterior rim of
the greater trochanter and the superior aspect of the cap-
sule of the hip. More recently, it has been reported to be at
the ventral triangular area of the greater trochanter.
6,7
The
French literature has it at the tubercule
prétrochantinien.
8
The function of gluteus minimus is also uncertain. Both
minimus and medius have been described as having essen-
tially the same function, primarily abduction, with internal
rotation and flexion being possible, depending on the
position of the femur.
1-3,9
Based on anatomical and electromyographic studies,
Gottschalk, Kourosh and Leveau
10
proposed a different
model of the gluteus complex. They declared that the
primary function of the entire gluteus minimus and the
posterior part of gluteus medius is to stabilise the head of
the femur in the acetabulum during the gait cycle.
Our interest in this muscle was raised by the observa-
tion of a lateral indentation in the head of the femur in
patients with spastic diplegia of the hip (Fig. 1). In the
course of periacetabular osteotomy with an inter-
trochanteric osteotomy, we found gluteus minimus in this
indentation, separated by the capsule. We deduced that this
appearance was due to pressure by gluteus minimus as it
resisted superolateral migration of the head. Notching of
the head has previously been described in patients with
cerebral palsy and was attributed either to a taut liga-
mentum teres,
11
the overlying capsule, spastic abductor
muscles,
12,13
or to the rim of the acetabulum.
14
Materials and Methods
We studied the anatomy of gluteus minimus in 16 hips
from nine cadavers, of which eight were fresh and one
embalmed. There were nine right and seven left hips. The
age at death had varied between 45 and 80 years.
The dissection was carried out with the cadaver in the
lateral position. After removal of the skin and subcuta-
neous tissue, the fascia over gluteus maximus and medius
was incised in the interval between the two muscles.
Gluteus maximus was then detached from the ilium and
reflected posteriorly. Next, gluteus medius was dissected
off gluteus minimus in a distal-to-proximal and posterior-
to-anterior direction. Based on our anatomical findings, a
model of gluteus minimus was developed, attached to
plastic bones of a hemipelvis and proximal femur (Fig. 2).
A prosthetic hip was implanted to provide a normal range
of movement. The joint capsule was simulated using a
broad rubber sheet, glued to the anterosuperior circum-
ference of the acetabulum and to the intertrochanteric line
on the proximal femur. The muscle was divided into four
identical sectors, sector I being the most anterior and
sector IV, the most posterior. Each sector was represented
by a cord 2 mm thick, which was firmly fixed at its
insertion on the greater trochanter and directed through
pulleys on the capsule of the hip and at its origin. The
excursion of each cord was measured independently.
Schanz screws were inserted at right angles into the
greater trochanter to control and measure the degrees of
rotation and flexion. Three measurements were made for
each directional movement, starting with the hip in the
neutral position and the mean value was calculated. The
measurements were taken for flexion, external and internal
rotation in both the extended and flexed position, and for
abduction.
359THE ANATOMY AND FUNCTION OF THE GLUTEUS MINIMUS MUSCLE
VOL. 82-B, N
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Fig. 1a
Fig. 1b
Fig. 1c
A 14-year-old-girl with spastic diplegia. Figure 1a –
Preoperative radiograph with a superolateral inden-
tation of the head of the femur. Figures 1b and 1c
– Intraoperative view of the head (1) after osteot-
omy of the greater trochanter (2). Gluteus minimus
(3) is retracted superiorly, with excellent visual-
isation of the groove (4) in the head. Gluteus mini-
mus (3) is released and lies in the indentation. The
joint capsule is seen (5).
Fig. 2
A model of gluteus minimus. Four different sectors of the muscle are
represented by cords, guided through pulleys, which represent the attach-
ment to the capsule and the origin of the muscle. The excursion is
measured on the scale (left).
Results
The gluteus minimus muscle arises from the external iliac
fossa. From there the fibres converge, crossing the hip
anterolaterally to their insertion on the front of the greater
trochanter. The line of origin begins anteriorly 3 to 5 mm
below the anterior superior iliac spine and runs posteriorly,
parallel to the iliac crest to the iliac tubercule. From there it
follows the anterior gluteal line to the greater sciatic notch
from where the caudal portion of the muscle takes its origin
inside the pelvis (Fig. 3). The posteroinferior border of the
muscle covers the posterosuperior acetabulum and follows
the inferior gluteal line to the anteroinferior iliac spine.
Anteriorly, gluteus minimus arises from the ridge between
the anterosuperior and anteroinferior iliac spines.
The muscle fibres converge from the area of origin to a
tendinous insertion into the capsule of the joint. They
measure about 4 cm in length and blend with a fascia on the
surface of gluteus minimus. This fascia increases in thick-
ness and finally becomes the tendon of gluteus minimus at
its insertion into the capsule. The tendon then continues to
its insertion on a ridge lateral to the anterior triangular area
of the greater trochanter. The capsular insertion is irregular
and measures 10 to 15 mm mediolaterally and 20 to 25 mm
craniocaudally. The insertion on the greater trochanter
shows great variation between an irregular L-shape and a
triangular area on the greater trochanter (Fig. 4). The area
anterior and medial to the insertion may be covered with a
thin layer of fibrocartilage forming the bottom of a bursa
under the tendon of gluteus minimus.
The posterior fibres run in a dorsoventral direction to the
capsule and the anterior fibres in a craniocaudal direction.
They make an angle of approximately 75° with each other.
The anterior craniocaudal fibres follow an almost straight
course while the posterior fibres wind around the greater
trochanter. The relationship between the capsular and tro-
chanteric insertions changes during the arc of hip flexion.
In the neutral position, the posterior fibres alter their direc-
tion between 60° and 80° at the capsular insertion, whereas
the anterior fibres run straight. At 90° of flexion, all fibres
of muscle and tendon run straight from their origin to their
insertion on the trochanter.
There was a fan-shaped appearance to the musculature in
nine hips. In two, an accessory muscle was identified
arising directly from the lateral edge of the iliac crest
between the anterosuperior iliac spine and the iliac tuber-
cule and from the fascia covering gluteus minimus. Dist-
ally, it joined the tendon of gluteus minimus. The branch of
the superior gluteal nerve to the tensor fasciae latae passed
behind this muscle. Five specimens could not be classified
into either group; in these the muscle between the antero-
superior iliac spine and the iliac tubercle originated directly
from the lateral edge of the iliac crest, but was covered by
the fascia of gluteus minimus. As in the cases with the
accessory muscle, the nerve to tensor fasciae latae passed
behind these muscle fibres. In a subsequent dissection of
two specimens we found a sequential innervation of gluteus
minimus with four distinct branches coming from the supe-
rior gluteal nerve.
Muscle function. The model of gluteus minimus (Fig. 2)
allowed us to measure the excursion of the muscle in
standardised directions. On moving the hip from extension
to 100° of flexion in neutral rotation, sectors I and II
shortened, sector III remained unchanged and sector IV
elongated slightly (Fig. 5). With external rotation of the
extended hip, sector I elongated, sector II showed no
change in length of the muscle fibre and sectors III and IV
shortened. With internal rotation the entire muscle elongat-
ed increasingly from anterior to posterior (Fig. 6). With
internal rotation of the flexed hip, sectors I to III shortened
and sector IV showed no change in length. With external
rotation all the muscle fibres elongated (Fig. 7). Abduction
360 M. BECK, J. B. SLEDGE, E. GAUTIER, C. F. DORA, R. GANZ
THE JOURNAL OF BONE AND JOINT SURGERY
Fig. 3
Diagram of gluteus minimus showing the area of origin, excluding the
anteroinferior iliac spine and the reflected head of the rectus from inside
the pelvis at the greater sciatic notch.
Fig. 4
Diagram showing the differing areas of insertion of the tendon of gluteus
minimus on the greater trochanter.
caused increased shortening from sector IV to sector I, with
sector IV showing little change in length (Fig. 8).
Discussion
Generally, the origin of gluteus minimus has been defined
as from the external iliac fossa between the anterior and
inferior gluteal lines.
1-3,5
Platzer, in Pernkopf ’s textbook of
anatomy,
4
describes an origin from inside the pelvis. At the
greater sciatic notch the caudal muscle fibres cover the
bone as they come round, protecting the superior gluteal
artery and nerve from damage.
The presence of an accessory muscle anterior to gluteus
minimus has been described
3,5
and variously termed ‘glu-
361THE ANATOMY AND FUNCTION OF THE GLUTEUS MINIMUS MUSCLE
VOL. 82-B, N
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Fig. 5
Excursion of the muscle fibres during hip flexion from
0° to 100°.
Fig. 6
Excursion of the muscle fibres in extension of the hip in
internal and external rotation.
Fig. 7
Excursion of the muscle fibres in 90° flexion of the hip
in internal and external rotation.
Fig. 8
Excursion of the muscle fibres at abduction.
teus quartus’ or ‘gluteus scansorius’. This specific pattern
was present in two out of our 16 dissections. The function
of this accessory muscle remains unclear. A strong variant
is found in monkeys and is thought to rotate the hip
internally enabling them to climb trees (scansorius from
scandere (Lat), to climb).
3
Correspondingly, we observed
that with increasing hip flexion the anterior part of gluteus
minimus has a stronger action for internal rotation.
The function of gluteus minimus and gluteus medius was
thought to be the same, that is primary abduction of the
hip.
1,3,5
We found that gluteus minimus acts as a flexor and
an abductor of the hip and also as either an internal or
external rotator, depending on which part of the muscle is
active and on the position of the femur relative to the pelvis
(Fig 5). This can be explained by the orientation of the
muscle fibres and the change of direction of the tendon
fibres at the joint capsule. The muscle fibres of sector I
elongate during external rotation and are therefore able to
resist this movement, which may help to prevent anterior
dislocation of the natural or prosthetic hip. During passive
internal rotation all muscle fibres elongate increasingly
from anterior to posterior and are therefore able to resist
internal rotation. This may help to prevent impingement of
the femoral neck against the superomedial acetabular rim
and posterior dislocation of a prosthetic hip. When the
entire muscle is activated simultaneously, which theoret-
ically is possible because of its sequential innervation, the
forces for internal and external rotation are counterba-
lanced. In such a situation the femoral head is pulled into
the acetabulum and stabilised.
In the flexed hip, the musculotendinous fibres run
straight from their origin to the femoral insertion. The
muscle fibres of sectors I to III rotate the hip internally,
whereas the posterior fibres are inactive. During passive
external rotation the entire muscle is stretched and is
therefore able to resist external rotation.
We conclude that one of the primary functions of gluteus
minimus is to stabilise the head of the femur in its socket.
This has already been suggested from electomyographic
and anatomical studies,
10
and more recently by an MRI
investigation of the abductors.
15
The stabilising action
seems to be more important in the extended hip, because of
the stronger counterbalancing activity of the muscle. Tight-
ening the joint capsule, a function which does not depend
on the position of the hip, also adds stability. Furthermore,
the tendon serves as a physical barrier against superolateral
migration of the head since it passes over it (Fig. 9). This
plays an important role in a hip which lacks geometrical
stability, for example a dysplastic joint in which the head
may sublux anterolaterally. A lateral flattening, or even
indentation, of the head can be observed in such cases,
especially in spastic hips.
The limitation of the model of gluteus minimus is that
only passive excursions of the muscle fibres are measured.
We attribute shortening to contraction and elongation to the
ability to resist movement. Our study cannot, however,
imitate the activation and co-ordination of the different
parts of the muscle in real life.
Recurrent dislocation after total hip arthroplasty has been
attributed to inadequate myofascial tension.
16-18
To
enhance stability, anterior and distal advancement of the
greater trochanter has been recommended to increase the
tension in gluteus medius and minimus.
16,17
The capacity
of a trochanteric osteotomy to prevent dislocation of the hip
by restoring the correct tension to the soft-tissue sleeve
17
may be improved by including the insertion of minimus to
the trochanter. Care should be taken to identify the insertion
of gluteus minimus during the approach to the hip and to
restore its anatomy at closure.
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.
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363THE ANATOMY AND FUNCTION OF THE GLUTEUS MINIMUS MUSCLE
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