Ligament

DEFINITION:
a short band of tough, flexible fibrous
connective tissue which connects two bones
or cartilages at a joint or supporting an organ.

• HISTOLOGY:
• At the microscopic level, ligaments are much more
complex, being composed of cells called fibroblasts which
are surrounded by matrix.
• The cells are responsible for matrix synthesis and they are
relatively few in number and represent a small percentage
of the total ligament volume.
• Although these cells may appear physically and functionally
isolated, recent studies have indicated that normal
ligament cells may communicate by means of prominent
cytoplasmic extensions that extend for long distances and
connect to cytoplasmic extensions from adjacent cells, thus
forming an elaborate 3-dimensional architecture.

• Gap junctions have also been detected in
association with these cell connections raising
the possibility of cell-to-cell communication and
the potential to coordinate cellular and metabolic
responses throughout the tissue.
• Ligament microstructure can be visualized using
polarized light that reveals collagen bundles
aligned along the long axis of the ligament and
displaying an underlying "waviness" or crimp
along the length.
• Crimp is thought to play a biomechanical role,
possibly relating to the ligaments loading state
with increased loading likely resulting in some
areas of the ligament uncrimping, allowing the
ligament to elongate without sustaining damage

STRUCTURE:
Extracellular components consist of:
water
Type I collagen (70% of dry weight)
elastin
higher elastin content than tendons
lipids
proteoglycans
epiligament coat
present in some ligaments, not all
analogous to epitenon of tendons
Cellular component
the main cell type in both tendons and ligaments is the
fibroblast
both tendons and ligaments have low vascularity and cellularity

the crimped structure of the collagen fibre
bundles permits stretching by 10–15% before
failure.
This combination of strength and extensibility
enables ligaments to absorb more strain
energy per unit weight than any other
biological material, and makes them very
effective shock absorbers .

• Ligaments vs. tendons
– composition
• compared to tendons, ligaments have
–lower percentage of collagen
–higher percentage of proteoglycans and
water
–less organized collagen fibers
–rounder fibroblasts

 An important mechanical difference between
tendons and ligaments is that ligaments often
contain bundles of collagen fibres orientated
in a range of directions, presumably because
bones can be moved apart in a range of
directions, whereas the fibres in a tendon are
aligned only in the direction in which the
muscle pulls on the tendon.

• Two types of ligament bone insertion
– indirect (fibrous insertion):
• most common form of bone insertion
• superficial fibers insert into the
periosteum
• deep fibers insert directly into bone via
perforating collagen fibers called Sharpey
fibers
• at insertion, endotenon becomes
continuous with periosteum
• examples
–MCL inserting into proximal tibia

–direct (fibrocartilaginous
insertion):
• has both deep and superficial fiber insertion
• deep fibers
–have four transitional zones of increasing
stiffness that allow for force dissipation and
reduce stress concentration
»Zone 1 (tendon or ligament proper)
• consists of well aligned type I collagen
fibers with small amounts of
proteoglycan decorin

 Zone 2 (fibrocartilage)
 consists of types II and III collagen, with small
amoutns of type I, IX and X collagen, and
proteoglycans aggrecan and decorin
 Zone 3 (mineralized fibrocartilage)
 consists of type II collagen, with significant
amounts of type X collagen and aggrecan
 Zone 4 (bone)
 is made up of type I collagen, with high mineral
content
 examples
supraspinatus insertion

• FUNCTIONS:
a)STABILITY:
• One of the main functions of ligaments is mechanical
as they passively stabilize joints and help in guiding
those joints through their normal range of motion
when a tensile load is applied.
• Ligaments exhibit nonlinear anisotropic mechanical
behaviour and under low loading conditions they are
relatively compliant, perhaps due to recruitment of
"crimped" collagen fibres as well as to viscoelastic
behaviours and interactions of collagen and other
matrix materials.

• Continued ligament-loading results in
increasing stiffness until a stage is reached
where they exhibit nearly linear stiffness and
beyond this, then, ligaments continue to
absorb energy until tensile failure (disruption).

• b)VISCOELASTIC BEHAVIOUR:
• Another ligament function relates to its
viscoelastic behaviour in helping to provide joint
homeostasis.
• Ligaments "load relax" which means that
loads/stresses decrease within the ligament if
they are pulled to constant deformations.
• Ligaments also "creep" which is defined as the
deformation (or elongation) under a constant or
cyclically repetitive load.
• Creep is particularly important when considering
joint injury or reconstructive surgery as excessive
creep could result in laxity of the joint thus
predisposing it to further injury

• C)PROPRIOCEPTION:
• A third function of ligaments is their role in joint
proprioception, which is referred to as the conscious
perception of limb posi tion in space.
• In joints such as the knee, proprioception is provided
principally by joint, muscle and cutaneous receptors.
• When ligaments are strained, they invoke neurological
feedback signals that then activate muscular
contraction and this appears to play a role in joint
position sense.
• Although progress continues to be made to elucidate
the role of proprioception in normal ligament function
and during injury, more precise quantification is the
subject of ongoing analysis.

• Anterior sternoclavicular ligament:
• The anterior sternoclavicular ligament is
broad and attached above to the
anterosuperior aspect of the sternal end of
the clavicle.
• It passes inferomedially to the upper anterior
aspect of the manubrium, spreading onto the
first costal cartilage.
• Posterior sternoclavicular ligament :
• The posterior sternoclavicular ligament is a
weaker band posterior to the joint.
• It descends inferomedially from the back of
the sternal end of the clavicle to the back of
the upper manubrium

• Interclavicular ligament :
• The interclavicular ligament is continuous
above with deep cervical fascia, and unites the
superior aspect of the sternal ends of both
clavicles; some fibres are attached to the
superior manubrial margin.

• Acromioclavicular ligament:
• The acromioclavicular ligament is
quadrilateral.
• It extends between the upper aspects of the
lateral end of the clavicle and the adjoining
acromion.
• Its parallel fibres interlace with the
aponeuroses of trapezius and deltoid

• Coracoclavicular ligament :
• The coracoclavicular ligament connects the
clavicle and the coracoid process of the
scapula .
• Though separate from the acromioclavicular
joint, it is a most efficient accessory ligament,
and maintains the apposition of the clavicle to
the acromion.

• Coracohumeral ligament :
• The coracohumeral ligament is attached to the
dorsolateral base of the coracoid process and extends
as two bands, which blend with the capsule, to the
greater and lesser tubercles . Portions of the
coracohumeral ligament form a tunnel for the biceps
tendon on the anterior side of the joint.
• The rotator interval is reinforced by the coracohumeral
ligament.
• It also blends inferiorly with the superior
glenohumeral ligament.

• Anular ligament :
• This is a strong band, which encircles the radial
head,holding it against the radial notch of the
ulna.
• Forming about four-fifths of the ring, it is
attached to the anterior margin of the notch,
broadens posteriorly and may divide into several
bands.
• It is attached to a rough ridge at or behind the
posterior margin of the notch; diverging bands
may also reach the lateral margin of the trochlear
notch above and proximal end of the supinator
crest below.
• The proximal anular border blends with the
elbow joint capsule, except posteriorly where the
capsule passes deep to the ligament to reach the
posterior and inferior margins of the radial notch.

• From the distal ANULAR border a few fibres
pass over reflected synovial membrane to
attach loosely on the radial neck.
• The external surface of the anular ligament
blends with the radial collateral ligament and
provides an attachment for part of supinator.
• Subluxation of the radial head through the
anular ligament arising from a sudden jerk on
the arm is a relatively common injury in young
children (known as ‘pulled elbow’).

• This is because the anular ligament has
vertical sides in children compared with more
funnel-shaped sides in adults.

• Triangular fibrocartilage
complex (TFCC) and distal
radio-ulnar ligaments:
• The triangular fi brocartilage complex (TFCC) is a
ligamentous and cartilaginous structure which suspends
the distal radius and ulnar carpus from the distal ulna.
• The TFCC stabilizes the ulnocarpal and radio-ulnar joints,
transmits and distributes load from the carpus to the ulna,
and facilitates complex movements at the wrist .
• By definition,it is made up of the cartilaginous disc, the
meniscus homologue (an embryological remnant of the
‘ulnar’ wrist that is only occasionally present), volar and
dorsal distal radio-ulnar ligaments, ulnar collateral
ligament, floor of extensor carpi ulnaris subsheath,
ulnolunate and ulnotriquetral ligaments.

• FUNCTION:
a. The triangular fibrocartilage complex stabilizes
the wrist at the distal radioulnar joint.
b. It also acts as a focal point for force transmitted
across the wrist to the ulnar side.
• Traumatic injury or a fall onto an outstretched
hand is the most common mechanism of injury.
The hand is usually in a pronated or palm down
position.
• Tearing or rupture of the TFCC occurs when there
is enough force through the ulnar side of the
hyperextended wrist to overcome the tensile
strength of this structure.

• superficial and deep components of the distal
radio-ulnar ligaments which act as a functional
couple stabilizing the rotation of the ulnar
head on the sigmoid notch of the radius

• ligamenta flava : ligaments of the spine.
• They connect the laminae of
adjacent vertebrae, all the way from the
second vertebra, axis, to the first segment of
the sacrum.

• Function:
• Their marked elasticity serves to preserve the
upright posture, and to assist the vertebral
column in resuming it after flexion.
• The elastin prevents buckling of the ligament
into the spinal canal during extension, which
would cause canal compression.
• Clinical relevance:
• Hypertrophy of this ligament may cause spina
stenosis, particularly in patients with diffuse
idiopathic skeletal hyperostosis,]because it lies
in the posterior portion of the vertebral canal.

• Iliofemoral ligament:
• The iliofemoral ligament is very strong and
shaped like an inverted Y, lying anteriorly and
intimately blended with the capsule. Its apex
is attached between the anterior inferior iliac
spine and acetabular rim, its base to the
intertrochanteric line.

• FUNCTION:
• In a standing posture, when the pelvis is tilted
posteriorly, the ligament is twisted and tense,
which prevents the trunk from falling backwards
and the posture is maintained without the need
for muscular activity.
• In this position the ligament also keeps
the femoral head pressed into the acetabulum.
• As the hip flexes, the tension in the ligament is
reduced and the amount of possible rotations in
the hip joint is increased, which permits the
pelvis to tilt backwards into its sitting angle.
Lateral rotation and adduction in the hip joint is
controlled by the strong transversal part, while
the descending part limits medial rotation.

• Ischiofemoral ligament:
• The ischiofemoral ligament thickens the back of
the capsule and consists of three distinct parts.
The central part, the superior ischiofemoral
ligament, spirals superolaterally from the
ischium, where it is attached posteroinferior to
the acetabulum, behind the femoral neck to
attach to the greater trochanter deep to the ilio-

• Pubofemoral ligament:
• The pubofemoral ligament is triangular, its
base attaching to the iliopubic eminence,
superior pubic ramus, obturator crest and
obturator membrane.
• It blends distally with the capsule and deep
surface of the medial iliofemoral ligament.

• FUNCTION:
• The pubofemoral ligament stabilizes the hip
joint.
• It prevents the joint from moving beyond its
normal range of motion, front-to-back and
side-to-side.
• It also limits external rotation of the joint.
• The pubofemoral ligament is considered to be
a supporting element of the joint capsule.
• It reinforces the inferior and anterior capsule.

• Anterior cruciate ligament:
• The anterior cruciate ligament is attached to
the anterior intercondylar area of the tibia,
just anterior and slightly lateral to the medial
tibial eminence, partly blending with the
anterior horn of the lateral meniscus.
• It ascends posterolaterally, twisting on itself
and fanning out to attach high on the
posteromedial aspect of the lateral femoral
condyle .

• FUNCTION:
• it resist anterior translation & medial rotation
of the tibia,in relation to the femur.
• Congenital absence of the anterior cruciate
ligament is rare. The condition is usually
associated with lower limb dysplasia and may
be a cause of instability of the knee

• Posterior cruciate ligament:
• The posterior cruciate ligament is thicker and
stronger than the anterior cruciate ligament .
• It is attached to the lateral surface of the medial
femoral condyle and extends up onto the anterior
part of the roof of the intercondylar notch, where
its attachment is extensive in the anteroposterior
direction.
• They pass distally and posteriorly to a fairly
compact attachment posteriorly in the
intercondylar region and in a depression on the
adjacent posterior tibia.
• This gives a fan-like structure in which fibre
orientation is variable

• FUNCTION:it prevent the femur from sliding of
the anterior edge of tibia & to prevent the
tibia from displacing posterior to the tibia.

• Medial collateral ligament (deltoid
ligament):
• The medial collateral ligament (deltoid ligament) is a
strong, triangular band, attached to the apex and the
anterior and posterior borders of the medial malleolus
• Of its superficial fibres, the anterior (tibionavicular)
pass forwards to the navicular tuberosity, behind which
they blend with the medial margin of the plantar
calcaneonavicular ligament.
• intermediate (tibiocalcaneal) fibres descend almost
vertically to the entire length of the sustentaculum tali.
• posterior fibres (posterior tibiotalar) pass
posterolaterally to the medial side of the talus and its
medial tubercle.
• The deep fi bres (anterior tibiotalar) pass from the tip
of the medial malleolus to the non-articular part of the
medial talar surface.

• FUNCTION:
a) Superficial deltiod primarily resist eversion of
foot.
b) Tibionavicular portion suspends spring lig &
prevents inward displacement of head talus
,while tibiocalcaneal portion prevents valgus
displacement.
c) Deep deltiod lig extends the function of
medial malleolus& lateral displacement of
talus &prevents external rotation of talus.

• Lateral ligament :
• The lateral ligament has three discrete parts.
a) The anterior talofibular ligament extends
anteromedially from the anterior margin of the
fibular malleolus to the talus, attached in front
of its lateral articular facet and to the lateral
aspect of its neck .
FUNCTION:
a) Primary restraint to inversion in plantar flexion
b) Resists anterolateral translation of talus in he
mortise
 Weakest of the lateral lig ,so mst cmnly injured
in sprains.

B) The posterior talofibular ligament runs almost
horizontally from the distal part of the lateral
malleolar fossa to the lateral tubercle of the
posterior talar process a ‘tibial slip’ of fibres
connects it to the medial malleolus.
FUNCTION:
a. Plays only a supplementary role in ankle stabilty
when the lateral lig is intact.
b. Limits posterior talar displacement within the
mortise as well as talar external rotation.
c. if ATFL and CFL are incompetent then
– short fibres of PTFL restrict internal and external
rotation, talar tilt, and dorsiflexion;
– long fibres inhibit only external rotation, talar tilt, and
dorsiflexion

C) The calcaneofibular ligament, a long cord,
runs from a depression anterior to the apex of
the fibular malleolus to a tubercle on the
lateral calcaneal surface and is crossed by the
tendons of fibularis longus and brevis .
• FUNCTION:
a. primary restrain to inversion in neutral or
dorsiflexed position
b. restrains subtalar inversion, thereby limiting
talar tilt within mortise

• Calcaneonavicular
Ligament (Spring
Ligament):
– attaches from the
sustentaculum tali to
the inferior aspect of
the navicular
• Function
– static stabilizer of the
medial longitudinal
arch and head of the
talus

Ligament

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