The tensor fascia latae, or TFL, is a well-known hip muscle among
healthcare professionals and rehabilitation specialists. Because of its
function, this muscle may be responsible for pain and dysfunction in the lower
extremities, pelvis and spine. Research studies conclude however, that this
muscle is poorly understood and needs further examination. Furthermore, the
majority of research which has been already conducted have in fact simplified
the accurate anatomy of, not only the TFL, but also its anatomical relationship
to the iliotibial band, or ITB.
The TFL, or tensor fascia latae, is a complex muscle which is intricately
arrangement anatomically with the ITB, or iliotibial band, and it performs
various essential functions, such as allowing hip mobility as well as transmitting
fascial tension through the fascia latae located in the thigh and the
iliotibial band. The TFL also provides postural support during one-legged
stance and limits the tensile stress on the femur caused by the combination of
bodyweight, ground reaction force and how these create individual bending
forces against the femur.
Anatomy of the Tensor Fascia Latae and the ITB
When one discusses the anatomy of the TFL, the anatomy of the ITB should
also be discussed as these serve a conjoined role in order to function. A study
conducted to compare the TFL and ITB in humans to other primates and mammals
determined that human beings are the only mammals to have a defined ITB. The
study also further regarded the anatomy and function of both the tensor fascia
latae and the iliotibial band. Additional studies via cadaveric and
biomechanical modelling research added a substantial amount of knowledge about
this often misunderstood muscle, the TFL, and its relationship to the ITB.
The general agreement is that the tensor
fascia latae begins on the iliac crest which starts just lateral to the origin
of the sartorious, or ASIS, and extends posteriorly along the iliac crest to combine
several types of tissue into the iliac crest and onto the gluteal fascia. It’s
been highlighted that the muscle provides multiple functions and contains
anatomically distinct heads: the anteromedial, or AM, and the posterolateral,
or PM, head.
Available research describes that the muscle
has both a bony insertion onto the femur and a fascial insertion onto the
iliotibial band, or more specifically, onto the region of the middle
longitudinal layer of the fascia latae of the thigh, the iliotibial band.
Early studies perceived the ITB to be a ligament that connected the
ilium with the knee in order to help maintain the balance of the body while in
motion or when standing. Later studies demonstrated that human beings are the
only mammals to own a distinct fascial lateral band down the thigh, indicating
that the ITB may play a role in bipedal balance and stance.
Other studies demonstrated that the fascia latae of the thigh contains a
multifaceted array of layers which all attach. The middle longitudinal layer,
or MLL, of the fascia latae is a thick, connective tissue that originates on
the iliac crest and extends downwards into various insertions. A large part of
the MLL blends with the inner transverse layer of the fascia latae and is
introduced directly onto the femur. The middle longitudinal layer also has
superficial fibres that extend all the way down and insert into the knee.
Anteriorly at the hip, the MLL surrounds the TFL to ensure the muscle is
effectively joined between the superficial and deep middle longitudinal layer.
It also contains fibres which directly combines the superficial fibres of the gluteus
maximus The MLL is joined in part to the gluteus maximus and in part to the
TFL. As well as being enveloped by the middle longitudinal layer, some of the
distal fibres of both heads of the TFL then insert into the MLL. The anteromedial
fibres of the TFL fuse with the MLL and course down the thigh to introduce onto
the lateral patella retinaculum. This is believed to influence the position of
the patella in relation to the femoral trochlear groove.
Nevertheless, none of these tissues cross the knee joint, therefore they
have no effect on motion at the tibia. According to research, the primary
function of the muscles and tissues appears to be at the hip. Some of the
fibres of the posterolateral tensor fascia latae together with the tissues of
the gluteus maximus, contribute function for the MLL and attach all the way
down onto the lateral tubercle of the tibia. These do cross the knee joint and may
ultimately help stabilize the pelvis and the lower extremities.
Essentially, the MLL travels down the thigh and heavily combines with the
inner transverse layer of the fascia latae as it is largely developed and dense
within the upper third of the thigh. These transverse fibres run obliquely to
anchor strongly to the femur, making up the deep and thick intermuscular septum
of the femur. The septum effectively forms an osteo-fascial wall between the
anterior quadriceps muscle group and the posterior hamstring muscle group.
Fibres from the inner transverse layer also allow the superior fibres of
the gluteus maximus to develop an ascending tendon. The part of the tensor
fascia latae that did not combine with the middle longitudinal layer of the
tissue also combines with this rising tendon to insert directly onto the
intermuscular septum and the femur. In other words, the majority of the TFL
indirectly inserts onto the femur via the ascending gluteal tendon and
indirectly via the blending of the MLL to the thick transverse layer.
Further down the thigh, the iliotibial band continues as a thickened
section of the fascia latae, creating the fascial barrier between the anterior
quadriceps and the posterior hamstrings. It then completely envelops the thigh,
holding to the distal lateral femoral shaft through strong obliquely directed
fibrous strands and follows the patellar retinaculum. Because these fibrous tissues
divide the ITB into a proximal tendinous portion and a distal ligamentous
portion, it’s been concluded that the tensor fascia latae has very little
involvement in the mobility of the tibia and knee and its primary function is
directed at the hip.
Function of the Tensor Fascia Latae
Anteromedial fibres (AM)
The main function of the anteromedial fibres is to flex the hip during
open kinetic chain movements, such as hip flexion over the swing phase of gait,
as confirmed through EMG and electrical stimulation experiments. The muscle is
restricted upon heel strike which suggests that the muscle is required to be
inactive to allow hip extension to occur during stance phase. The muscle is
most active during the acceleration phase of running which also demonstrates
its main role as a powerful hip flexor.
During pure open kinetic-chain movement, the AM fibres are most active
in hip flexion movements as well as in abduction movements. It becomes
restricted though, if the hip is externally rotated whilst abducting. This
should be an important consideration when a healthcare professional is
recommending specific hip rehabilitation exercises for the gluteal muscles and
other hip external rotators.
Posterolateral fibres (PL)
The posterolateral fibres are most active during the stance phase of
gait. This suggests that the muscle acts as a major hip stabilizer during
single leg stance as it activates its role as a hip abductor. In this process,
the superior portion of the gluteus maximus is also active during walking
phase. Considering that the PL head has fibres that join the tendon from the
superior gluteus maximus, this proposes that the posterolateral fibres and
superior gluteus maximus cooperate to control the stability of the pelvis
during stance phase.
Both the tensor fascia latae and gluteus maximus apply their role as a
hip muscle through the contribution they have with the MLL, the deep transverse
layer of the fascia latae and the intermuscular septum. They effectively insert
onto the femur through this complex system of fascia and are considered muscles
which begin at the pelvis which are introduced onto the femur. In pure open
kinetic chain movements, the PL, or posterolateral fibres, are active in all
hip internal rotation movements and in abduction movements. Similar to the AM fibres,
the PL fibres remain restricted if the hip is abducting whilst in external
rotation.
Function of the TFL at the Knee
A majority of the comprehensive studies examining the role of TFL in
relation to the movements of the knee and the stability of the patella find it
challenging to identify a direct function for the TFL in knee function. It
almost certainly does not contribute to knee extension, flexion or rotation. As
a result, all previous descriptions of the TFL being a synergistic knee
extender with the quadriceps or an externally rotator of the tibia can almost
certainly be rejected. It’s also been concluded that the TFL does not play an
active role in pulling the patella laterally. The most likely role the TFL has
in knee patella stability is indirectly, through maintaining the tension in the
fascia latae and the distal portion of the ITB that combines with the patella
retinaculum.
The TFL as a Fascial Tensioner
Several studies have demonstrated that the tensor fascia latae also
functions to maintain fascia tension during movement. This is primarily due to
a complex arrangement of fascial planes of various thicknesses which have
development over the thigh. It has a loose anterior and posterior layer which
cover the quadriceps and hamstrings. The loose anterior superficial layer of
the TFL would gather during knee extension movements if there did not exist
some manner of tensioning system for the fascia to maintain the fascial
envelope. In the same manner, the posterior fascia latae would most likely
gather during knee flexion movements.
Based on their anatomical arrangement with the fascia latae, the muscles
which can maintain this fascial tension during knee movements include the TFL
anteriorly and the superior gluteus maximus posteriorly. The TFL must then
become slightly active during knee extensions to progressively shorten the
fascia upwards whilst the knee is extended, to prevent the anterior fascia from
creasing and twisting. Similarly, the gluteus maximus can maintain fascial
tension during knee flexion movements.
The Tensile Force of the Femur
One of the most extraordinary roles assigned to the ITB is the role it
has in reducing the bending and tensile force on the lateral femur. Humans walk
on two feet, which means that during a section of the gait cycle, they are in a
one-leg stance. This can create large lateral femur tensile forces and medial
femur compression forces which, if not properly monitored, could develop a
varus effect of the femur and essentially bend the femur.
During a study, researchers investigated the function of the ITB and
concluded that the varus bending forces on the femur could be partially
relieved by tensioning the iliotibial band. Other studies analyzed the stresses
on the femur caused by the varus force on the bone and also found that by
increasing the tension in the ITB, the lateral tension force and the medial
compression force on the femur would both ultimately limited. The study also
suggests that the TFL and gluteus maximus may add further tension to the ITB
and lessen this lateral tension force on the femur. Figure
2: Ober test
TFL Complications
For all the TFL issues that affect many individuals, almost nothing
exists in the literature that highlights the role this muscle has in
dysfunction. All theories and ideas are based on clinical reasoning and
assumptions. The most interesting observation regarding TFL complications is
the role it has in causing hip internal rotation/flexion during the stance
phase of gait.
Frequently, many individuals who report lower limb injuries caused by
overuse or low back and sacroiliac joint pain are commonly diagnosed with an
exaggerated hip flexion/internal rotation position during the functional
movements of a single extremity. The stance suggests an internally rotated and
flexed position.
This complication then develops what is known as a valgus collapse at
the joint of the knee, directly affecting the Q angle of the knee. With an
increase in the Q angle, the patella often tends to drag laterally and compress
against the lateral femoral condyle. This may then lead to patellofemoral pain
at the knee. This is believed to occur because the TFL maintains the stability
of the pelvis during one-leg stance by beginning its abduction role. The tensor
fascia latae may also display its hip flexion/internal rotation role. The
gluteus maximus, and other hip external rotators, should provide and equal
opposite external rotation/extension role.
The gluteus medius and minimus primarily function on the hip joint by contributing
a compressive and stabilizing role. These work little to assist in maintaining
a stable pelvic position. Instead, this role is assigned to the tensor fascial
latae and gluteus maximus.
The TFL is a significant muscle in pelvic dysfunction because it has the
greatest mechanical advantage to influence the pelvis and hip joint. It is the
most anterior muscle at the front of the hip, as a result, it’s believed to
have the greatest leverage advantage to encourage a flexion posture or an
anterior tilt of the ilium. Observing the hip from the front, the tensor fascia
latae is also the most lateral muscle on the hip. Therefore, it has the
greatest leverage to affect abduction of the hip. This explains how such a
small muscle can have such a large influence.
Furthermore, because the complex structures surrounding the lower back,
buttocks, hip/pelvis and leg can become directly affected causing pain,
irritation and inflammation as a result of TFL complications, other structures
of the body can be greatly affected as well. The sciatic nerve is the largest
single nerve found in the body and it runs through, the lower back, buttocks
and leg. The nerve is tightly surrounded by muscles and other tissues. When
these surrounding tissues are altered, the sciatic nerve can be easily compressed,
causing symptoms of sciatica. Sciatica is described as a set of symptoms rather
than a single condition. The most common symptoms of sciatica include: lower
back/buttock/hip/leg pain, burning and tingling sensations, and numbness.
While the following tests can be used to determine the presence of TFL
complications, a proper diagnosis can help differentiate whether the individual
is experiencing sciatica as a result of tensor fascia latae dysfunction or due
to another serious complication. Chiropractors are healthcare professionals who
specialize in musculoskeletal and nervous system injuries and conditions.
Chiropractic care offers a form of alternative treatment which uses spinal
adjustments and manual manipulations to carefully diagnose a variety of
injuries or conditions and decrease or eliminate the symptoms of sciatica which
may also be associated with TFL. In addition, an individual may follow through
with chiropractic treatment to also find relief from their tensor fascia latae
dysfunction after determining its presence with the next set of tests.
Chiropractic for Sciatica Symptoms
Assessing TFL Issues
To properly assess the tightness in the TFL, utilizing an Ober Test or a
Thomas test can help.
Ober test
Start position
The individual must be positioned on their side with the unaffected side
facing down. The pelvis and spine should be in neutral alignment with the
bottom leg flexed for support. The uppermost leg is extended above the
horizontal. The hip is then laterally rotated and extended, as long as no
lumbar extension occurs.
Movement
The individual must actively flatten their waist towards the floor and
hold their leg in slight abduction and lateral rotation. The individual will
then be instructed to slowly and carefully lower their leg towards the floor
until the tensor fascia latae and the iliotibial band hangs on the greater
trochanter and cannot lower any further. The key to an accurate test is to not
allow the pelvis to move, either into a lateral tilt, anterior tilt or
rotation. As the leg lowers, the hip should not flex or medially rotate. It’s
essential for the individual to maintain the laterally rotated position of the
hip. Ideally, the leg should lower into at least 10 to 15-degree adduction
without losing the proximal control of the pelvis or hip. The tensor fascia
latae and iliotibial band may lack elasticity if the leg does not adduct
sufficiently.
Thomas test
On a plinth, the individual should lie supine with the untested leg held
in hip flexion. The tested leg is then forced into extension and adduction. If
the tested leg is unable to attain a horizontal alignment and is held in
flexion and/or abduction, this is indicative of tightness in the tensor fascia
latae.
Managing TFL Issues
To manage the overactive or tight tensor fascia latae, 2 important
criteria must be met. First, it must be stretched and then, it must be massaged
and manipulated. The most effective stretch for the TFL is the knee-down hip
flexor stretch.
To stretch the left TFL, first, the individual should kneel on the left
knee with the right leg at 90-degrees hip flexion and knee flexion. Second, the
individual must push their left hip forward until the slack is taken up. Third,
by placing the hands on the right thigh, the individual will follow by twisting
the trunk around to the right whilst the pelvis remains facing forward,
inducing an external rotation of the hip to add to the rotation component of
the stretch. Then, if the individual has any slack left, they must push their
left leg outwards. Finally, the individual must isometrically contract the
right hamstring by attempting to drag the left heel backwards. To stretch the
right TFL, the same procedures should be followed but using the opposite leg.
To self-massage or trigger the TFL, the individual should lie on their
side and place a trigger ball/Muscle Mate/Posture Pro under the tensor fascia
latae in order to apply gentle pressure. The hip, knee and ankle should remain
in a straight line with the body. This can be performed as a rolling type
movement or as sustained pressure to relieve the trigger points within the
muscle, ultimately helping to reduce the painful symptoms associated with TFL
dysfunction, among other serious complications which may need medical attention
as soon as possible.
By Dr. Alex Jimenez
