Anatomy of the Knee Joint

KNEE JOINT
 The knee joint is the largest and
most complicated joint in the
body.
 Basically, it consists of two
condylar joints between the
medial and lateral condyles of
the femur and the
corresponding condyles of the
tibia, and a gliding
joint, between the patella and
the patellar surface of the
femur.
 The fibula is not directly
involved in the joint.
Dr M Eladl

TYPE
 Is a synovial joint of the
condylar variety.
 It can by regarded as a
modified hinge variety (because
it allows some rotatory
movements beside flexion and
extension).
Dr M Eladl

ARTICULATION
 Above: the rounded condyles of
the femur;
 Below: the condyles of the tibia
and their cartilaginous menisci
 In front: Is the articulation
between the lower end of the
femur and the patella.
 The articular surfaces of the
femur, tibia, and patella are
covered with hyaline cartilage.
 Note that the articular surfaces
of the medial and lateral
condyles of the tibia are often
referred to clinically as the
medial and lateral tibial
plateaus. Dr M Eladl

CAPSULE
 Attached to the margins of the
articular surfaces & surrounds
the sides and posterior aspect
of the joint.
 On the front of the joint, the
capsule is absent, permitting
the synovial membrane to
pouch upward beneath the
quadriceps tendon, forming the
suprapatellar bursa.
 On each side of the patella, the
capsule is strengthened by
expansions from the tendons of
vastus lateralis and medialis.
Dr M Eladl

CAPSULE
 Behind the joint, the capsule is
strengthened by an expansion
of the semimembranous muscle
called the oblique popliteal
ligament.
 An opening in the capsule
behind the lateral tibial condyle
permits the tendon of the
popliteus to emerge.
Dr M Eladl

LIGAMENTS
 Ligaments may be divided
into
1) Extracapsular ligaments:
Those that lie outside the
capsule.
2) Capsular ligaments
Those that are thickend
parts of the capsule.
3) Intracapsular Ligaments
Those that lie within the
capsule.
Dr M Eladl

LIGAMENTUM PATELLAE
 It is, in fact, the
continuation of the central
portion of the common
tendon of the quadriceps
femoris muscle.
 Attached
 Above: to the lower border
of the patella
 Below: to the tibial
tuberosity.
 Rupture of the Ligamentum
Patellae:
Can occur when a sudden
flexing force is applied to
the knee joint when the
quadriceps femoris muscle
is actively contracting.
Dr M Eladl

LATERAL COLLATERAL LIGAMENT
 Cordlike and is attached
above to the lateral
condyle of the femur and
below to the head of the
fibula.
 The tendon of popliteus
muscle intervenes between
the ligament and the
lateral meniscus.
 Forced adduction of the
tibia on the femur can
result in injury to the
lateral collateral ligament
(less common than medial
ligament injury).
Dr M Eladl

MEDIAL COLLATERAL LIGAMENT
 Flat band and is attached
above to the medial
condyle of the femur and
below to the medial surface
of the shaft of the tibia.
 It is firmly attached to the
edge of the medial
meniscus.
Dr M Eladl

MEDIAL COLLATERAL LIGAMENT
 Forced abduction of the
tibia on the femur can
result in partial tearing of
the medial collateral
ligament, which can occur
at its femoral or tibial
attachments.
 It is useful to remember
that tears of the menisci
result in localized
tenderness on the joint
line, whereas sprains of the
medial collateral ligament
result in tenderness over
the femoral or tibial
attachments of the
ligament. Dr M Eladl

OBLIQUE POPLITEAL LIGAMENT
 Is a tendinous expansion
derived from the
semimembranosus muscle.
 It strengthens the posterior
aspect of the capsule.
Dr M Eladl

ARCUATE POPLITEAL LIGAMENT
 It is a Y-shaped thickening of
the posterolateral
capsule, which arises from the
fibular styloid and divides into
two limbs:
 Medial limb: curves over the
popliteus muscle to join with
the oblique popliteal ligament
 lateral limb: ascends to blend
with the capsule near the
lateral head of gastrocnemius
muscle.
Dr M Eladl

INTRACAPSULAR LIGAMENTS
 The cruciate ligaments are
two strong intracapsular
ligaments that cross each
other within the joint
cavity.
 They are named anterior
and posterior, according to
their tibial attachments.
 These important ligaments
are the main bond between
the femur and the tibia
throughout the joint's
range of movement.
Dr M Eladl

ANTERIOR CRUCIATE LIGAMENT
 Attached to the anterior
intercondylar area of the
tibia
 Passes
upward, backward, and
laterally, to be attached to
the posterior part of the
medial surface of the
lateral femoral condyle
 Functions:
 Prevent anterior
displacement of the tibia
with the knee flexed.
 Prevents posterior
displacement of the femur
on the tibia.
Dr M Eladl

POSTERIOR CRUCIATE LIGAMENT
 Attached to the posterior
tibia.
 Passes upward, forward,
and medially to be attached
to the anterior part of the
lateral surface of the
medial femoral condyle
Dr M Eladl

POSTERIOR CRUCIATE LIGAMENT
 Attached to the posterior
tibia.
 Passes
upward, forward, and
medially to be attached to
the anterior part of the
lateral surface of the
 Functions:
 Prevent posterior
displacement of the tibia
with the knee flexed.
 Prevents anterior
displacement of the femur
on the tibia.
Dr M Eladl

MENISCI
 The menisci are C-shaped
sheets of fibrocartilage.
 The upper surfaces are in
contact with the femoral
condyles.
 The lower surfaces are in
contact with the tibial
condyles.
 The peripheral border is
thick and attached to the
capsule
 The inner border is thin
and concave and forms a
free edge.
Dr M Eladl

MENISCI
 Each meniscus is attached
to the upper surface of the
tibia by anterior and
posterior horns.
 Because the medial
meniscus is also attached
to the medial collateral
ligament, it is relatively
immobile.
 Functions:
 Deepen the articular
surfaces of the tibial
condyles to receive the
convex femoral condyles
 Serve as cushions between
the two bones.
Dr M Eladl

SYNOVIAL MEMBRANE
 Lines the capsule and is
attached to the margins of
the articular surfaces.
 On the front and above the
joint, it forms a
pouch, which extends up
beneath the quadriceps
femoris muscle for three
fingerbreadths above the
patella, forming the
suprapatellar bursa.
 This is held in position by
the attachment of a small
portion of the vastus
intermedius muscle, called
the articularis genu
muscle.
Dr M Eladl

SYNOVIAL MEMBRANE
 At the back of the joint, it is
prolonged on the deep
surface of the tendon of the
popliteus, forming the
popliteal bursa.
 A bursa is interposed
between the medial head of
the gastrocnemius and the
and the semimembranosus
tendon; this is termed the
semimembranosus
bursa, and it frequently
communicates with the
synovial cavity of the joint.
Dr M Eladl

SYNOVIAL MEMBRANE
 It is reflected forward from
the posterior part of the
capsule around the front of
the cruciate ligaments. As a
result, the cruciate
ligaments lie behind the
synovial cavity and are not
bathed in synovial fluid.
 In the anterior part of the
joint, it is reflected
backward from the
posterior surface of the
ligamentum patellae to
form the infrapatellar fold;
the free borders of the fold
are termed the alar folds.
Dr M Eladl

BURSAE RELATED TO THE KNEE
JOINT
 Number: ten bursae are
related to the knee joint.
 They are found wherever
skin, muscle, or tendon
rubs against bone.
 Four are situated in front
of the joint and six are
found behind the joint.
 The suprapatellar and the
popliteal bursa always
communicate with the
joint, and the
semimembranosus bursa
may communicate with the
joint.
Dr M Eladl

ANTERIOR BURSAE
 Suprapatellar bursa: lies
beneath the quadriceps
muscle and communicates
with the joint cavity.
 Prepatellar bursa: lies in
the subcutaneous tissue
between the skin and the
front of the lower half of
the patella and the upper
part of the ligamentum
patellae.
Dr M Eladl

ANTERIOR BURSAE
 Superficial infrapatellar
bursa: lies in the
subcutaneous tissue
between the skin and the
front of the lower part of
the ligamentum patellae.
 Deep infrapatellar bursa:
lies between ligamentum
patellae and the tibia.
Dr M Eladl

POSTERIOR BURSAE
 Popliteal bursa: is found in
association with the tendon
of the popliteus and
communicates with the
joint cavity.
 Semimembranosus bursa:
is found related to the
insertion of the
semimembranosus muscle
and may communicate with
the joint cavity.
Dr M Eladl

POSTERIOR BURSAE
 The remaining four bursae
are found related to:
 Tendon of insertion of the
biceps femoris;
 Tendons of the
sartorius, gracilis, &
semitendinosus muscles as
they pass to their insertion
on the tibia;
 Beneath the lateral head of
origin of the gastrocnemius
muscle; and
 Beneath the medial head of
origin of the gastrocnemius
muscle.
Dr M Eladl

NERVE SUPPLY OF KNEE JOINT
 Number: ten nerves.
1) Femoral nerve: gives twigs
from the nerves to the
three vasti.
2) Tibial nerve: gives:
1) Superior medial genicular.
2) Inferior medial genicular.
3) Middle genicular nerve.
3) Common peroneal nerve:
gives:
1) Superior lateral genicular.
2) Inferior lateral genicular.
3) Recurrent genicular nerve.
4) Obturator nerve: gives the
genicular branch from its
posterior division Dr M Eladl

ARTERIAL SUPPLY OF KNEE JOINT
 Number: ten arteries.
 Femoral artery:
1) Descending genicular.
2) Descending branch of the
lateral circumflex femoral.
 Popliteal artery:
1) Superior medial genicular.
2) Inferior medial genicular.
3) Middle genicular artery.
4) Superior lateral genicular.
5) Inferior lateral genicular.
 Anterior tibial artery:
1) Posterior tibial recurrent.
2) Anterior tibial recurrent.
 Posterior tibial artery: -
Circumflex fibular.
Dr M Eladl

MOVEMENT OF KNEE JOINT
 Flexion:
Mainly by: biceps femoris, semitendinosus
Assisted by: sartorius, gracilis and popliteus muscles.
 Extension:
Mainly by: Quadriceps femoris muscle.
Assisted by: tensor fasciae lata muscle.
 Medial rotation:
Mainly by: popliteus muscle.
Assisted by: sartorius, gracilis, semitendinosus &
semimembranosus.
 Lateral rotation:
Only done by the biceps femoris muscle.
Dr M Eladl

LOCKING OF KNEE JOINT
 Definition:
Is the terminal stage of full
extension of the knee joint.
 Mechanism:
 The leg (the tibia) is laterally
rotated & the thigh (the femur) is
medially rotated.
 This rotatory movement locks the
joint (which means that the joint
cannot be flexed unless it is
unlocked by the reverse rotation).
 In full extension with the locked
knee, all the ligaments are
stretched and the joint is stable.
 Produced by biceps femoris
muscle (the only lateral rotator)
Dr M Eladl

UNLOCKING OF KNEE JOINT
Dr M Eladl
 Definition:
Is the early stage of flexion of the
knee joint.
 Mechanism:
The leg is medially rotated and the
thigh is laterally rotated.
 Muscles produce unlocking:
This is done by the action of:
 Popliteus muscle,
helped by:
 Semimembranosus, semitendinos
us & gracilis muscles

STRENGTH OF THE KNEE JOINT
 The strength of the knee
joint depends on:
1) Strength of the ligaments
that bind the femur to the
tibia.
2) Tone of the muscles acting
on the joint.
 The most important muscle
group is the quadriceps
femoris; provided that this
is well developed, it is
capable of stabilizing the
knee in the presence of torn
ligaments.
Dr M Eladl

PNEUMOARTHROGRAPHY
 Air can be injected into
the synovial cavity of the
knee joint so that soft
tissues can be studied.
 This technique is based on
the fact that air is less
radiopaque than
structures such as the
medial and lateral
menisci, so their outline
can be visualized on a
radiograph .
Dr M Eladl

ARTHROSCOPY
 Introduction of a lighted
instrument into the
synovial cavity of the knee
joint through a small
incision.
 This technique permits
the direct visualization of
structures, such as the
cruciate ligaments and
the menisci, for
diagnostic purposes

INJURIES OF THE KNEE JOINT
 Knee joint injuries are common because:
1. It is a low-placed joint.
2. Mobile.
3. Weight-bearing joint,
4. Serving as a fulcrum between two long levers (thigh and
leg).
5. Its stability depends almost entirely on its associated
ligaments and surrounding muscles.
6. The knee joint is essential for everyday activities such as
standing, walking, and climbing stairs.
7. It is also a main joint for sports that involve
running, jumping, kicking, and changing directions.
To perform these activities, the knee joint must be mobile;
however, this mobility makes it susceptible to injuries.
Dr M Eladl

INJURIES OF THE KNEE JOINT
 The most common knee
injuries in contact
sports are ligament
sprains, which occur
when the foot is ﬁxed in
the ground.
 If a force is applied
against the knee when
the foot cannot
move, ligament injuries
are likely to occur.
Dr M Eladl

KNEE INJURY &THE SYNOVIAL
MEMBRANE
 Synovial membrane of knee
joint is extensive, & if the
articular surfaces, menisci, or
ligaments are damaged, the
large synovial cavity becomes
distended with fluid.
 The wide communication
between the suprapatellar
bursa and the joint cavity
results in this structure
becoming distended also.
 The swelling of the knee
extends 3 or 4 fingerbreadths
above the patella and laterally
and medially beneath the
aponeuroses of insertion of
the vastus lateralis and
medialis, respectively.
Dr M Eladl

TIBIAL COLLATERAL LIGAMENT
INJURY
 The firm attachment of the
TCL to the medial meniscus
is of considerable clinical
significance because tearing
of this ligament frequently
results in concomitant
tearing of the medial
meniscus.
 This injury is common in
athletes who twist their
flexed knees while running
(e.g. , in basketball, the
various forms of
football, and volleyball).
Dr M Eladl

UNHAPPY TRIAD OF THE KNEE
JOINT
 The ACL, which serves as a
pivot for rotatory
movements of the knee and
is taut during flexion, may
also tear subsequent to the
rupture of the
TCL, creating an “unhappy
triad” of knee injuries.
Dr M Eladl

JOINT
Dr M Eladl

JOINT
 Examination of patients with a
ruptured anterior cruciate
ligament shows that the tibia
can be pulled excessively
forward on the femur.
 Examination of patients with
rupture of the posterior
cruciate ligament, the tibia can
be made to move excessively
backward on the femur .
Dr M Eladl

LATERAL MENISCUS INJURY
 Injury to the lateral
meniscus is less
common, probably because
it is not attached to the
lateral collateral ligament
of the knee joint and is
consequently more mobile.
 The popliteus muscle sends
a few of its fibers into the
lateral meniscus, and these
can pull the meniscus into
a more favorable position
during sudden movements
of the knee joint.
Dr M Eladl

Anatomy of the Knee Joint

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Anatomy of the Knee Joint