Download THE KNEE JOINT: 4 bones: femur, tibia, patella and fibula 3

THE KNEE JOINT:
4 bones: femur, tibia, patella and
fibula
3 separate joints: tibiofemoral,
patellofemoral, and tibiofibular
joint
Function: allows certain
movements, restricts others, and
provides load transfer through the
lower limb.
JOINT MOTIONS:
3 translations
3 rotations
ANATOMY
ANTERIOR VIEW
Femur
-medial
-lateral condyles
Tibia
Patella
Fibula
LATERAL ANATOMY:
Lateral Supracondylar line
L. intermuscular septum
Lateral epicondyle
Lateral condyle
Tibial plateau
Lateral tibial condyle
Gerdy’s tubercle
Tibial tuberosity
Apex of fibular head
“styloid process”
Fibular head
MEDIAL ANATOMY:
Femur: Adductor Tubercle
- distal end of adductor
magnus tendon
- uppermost part of MCL
Medial epicondyle
Tibia: Medial condyle
Tibial plateau
FEMUR: INTERCONDYLAR
FOSSA
Separates the medial and lateral
femoral condyles posteriorly
-within the capsule
-not part of articular surface
therefore, not
covered by articular
hyaline cartilage.
Posterior intercondylar fossa (tibia)
Popliteal surface
Medial/Lateral supercondylar line
-VM, AddM,/BF, plantaris
TIBIOFIBULAR JOINT:
The fibula is attached to the tibia
proximally with ligaments, and
along its length by the interosseous
membrane.
Tib/Fib joint + ligaments of talus,
calcaneus and tibia allow very little
motion between fibula and tibia.
- Fixed joint
- Head of the fibula moves with
ankle motion
MENISCUS:
Lateral meniscus
Medial meniscus
Transverse meniscal ligament
Posterior menisco-meniscal
ligament
Anterior/Posterior horn
-attached to intercondylar
tibial plateau
-vascular like periphery
MENISCOFEMORAL
LIGAMENTS:
Anterior meniscofemoral ligament
(Ligament of Humphry)
Posterior meniscofemoral ligament
(Ligament of Wrisberg)
Increase stability of the knee joint
by moving the lateral meniscus
slightly medially and anteriorly
when the knee is in flexion.
VASCULAR/NERVOUS:
Femoral artery
Popliteal artery
Popliteal vein
Tibial nerve
Sural n.
Common peroneal n.
Peroneal communicating n.
Saphenous n
Genicular arteries
SYNOVIAL FLUID:
Decreases viscosity at high shear
rates
The high viscosity helps to
maintain a fluid film by resisting
squeezing out with the joint at rest.
PATELLA:
Medial contact of femur in
extreme flexion (rose)
Facet for medial femoral condyle
Facet for lateral femoral condyle
Attachment of patellar ligament
Lateral release
4 x’s body weight with knee flexed 70-80 degrees of flexion
ACL:
Primary restraint to anterior
translation of the tibia and
contributes the most at 30° flexion.
-Prevents hyperextension of
the knee
- Secondary restraint to
internal tibial rotation
- Resists adduction and
abduction at full extension
- 'guides' the screw home
rotation of the knee joint
as it approaches terminal
extension
ACL:
-Footprint
-Roof of intercondylar
notch during extension
-Difficulty in placement
of ACL
BUNDLES of ACL:
2 functional units:
Anteromedial bundle
taut in flexion
Posterolateral bundle
taut in extension
-Increases knee stability
-Likelihood of partial ruptures in
these positions
PCL:
Primary restraint
posterior translation of tibia
Secondary restraint
external tibial rotation at
90° flexion, which reduces
upon knee extension
Near full knee extension, the
anterior bundle of the PCL
slackens, and the posterolateral
structures become the primary
restraint.
PCL footprint
No fan out like the ACL
The fibers are almost parallel to
bone
Medial collateral ligament
functional units
The medial collateral ligament is
the primary restraint to abduction
and internal tibial rotation.
Secondary role of MCL:
Provides anterior knee stability,
which is enhanced by external tibial
rotation.
With anterior cruciate disruption
the medial collateral ligament
provides most of the anterior
stability of the knee.
Stabilising role of the lateral
collateral ligament
Primary restraint to adduction of
the knee
Secondary restraint to anterior and
posterior drawer, when the drawer
displacements are large. Combined
with the other lateral structures the
lateral collateral ligament is a
significant restraint to external
rotation of the tibia.
Meniscal biomechanics and
Functional anatomy
Medial meniscus has a firm bond to
MCL
Lateral meniscus has no attachment
to LCL
Because the popliteus tendon
attaches to the posterolateral corner
of the lateral meniscus, there is
some additional mobility and
decreased vascularity in this
location.
The transverse ligament joins the
anterior horns of the two menisci.
Posterolateral rotatory instability
Frequently, the lateral collateral
ligament, fabellofibular ligament,
and popliteofibular ligament are
ruptured together. This results in an
increase in external tibial rotation at
all angles of knee flexion and
adduction and posterior drawer
from 0 to 60° flexion with external
tibial rotation.
Varus-valgus test
A varus or valgus moment is
applied at full extension and
approximately 30° knee flexion.
The MCL is the primary restraint
against valgus moments at 30°
flexion whereas it is a secondary
restraint at full extension. The LCL
is a primary restraint against varus
moments over the range 5 to 25°
flexion. This test assesses medial or
lateral capsule or ligament damage.
Anteromedial rotary instability test
The tibia is rotated externally and
an anterior drawer test is carried
out at 90° flexion. This test
illustrates posteromedial capsule,
MCL, and ACL disruption. When
the MCL is intact, tibial external
rotation tightens it and anterior
drawer is less than in neutral
rotation.
Tests for posterolateral instability
Damage to the posterolateral
structures causes external tibial
rotation at all angles of knee
flexion. PCL damage allows the
tibia to also displace posteriorly
during external rotation at 90° knee
flexion, exaggerating the motion of
the fibula relative to the lateral
femoral condyle.
Posterolateral drawer test - knee
flexed between 60 and 90° flexion
and the foot rotated externally, the
lateral tibial plateau will displace
posteriorly.
The pivot shift test
Reduction test - knee is flexed from
full extension under a valgus
moment.
Subluxation test - reverse of
reduction test. The knee is extended
from a flexed position under a
valgus moment.
Both tests assess for anterolateral
instability, which is caused by a full
tear of the anterior cruciate
ligament, sometimes combined
with injuries to the lateral
structures, such as a stretching of
the lateral collateral ligament.
Patellar tendon
The patellar tendon is one of the
longest collagenous structures of
the body and is designed to
transmit very high tensile loads.
Maximum stress and modulus of
the patellar tendon have been
reported as double that of the
cruciate ligaments from the same
knee (Butler et al, 1986). During
normal daily activity such as
walking and stair climbing, the
tensile force in the patellar tendon
can reach three times bodyweight.
Typically occur in older patients
with associated joint space
narrowing. They may present with
loading type pain or mechanical
symptoms such as catching. At
arthroscopy, preservation of as
much meniscal tissue as possible
should be the principle. Patients
with significant joint space
narrowing should be warned
beforehand that partial
meniscectomy may not provide the
degree of pain relief that the patient
may expect, and that progression of
the arthritic process can be
expected. If indicated, an extensive
synovectomy and removal of any
impinging osteophytes should be
part of the procedure
p
complications. The portal of
bacterial entry may be a graze or
laceration near the knee, infected
eczema or athlete's foot more
distally.
Treatment of the inflamed bursa
includes prevention of further
mechanical irritation, rest and antiinflammatory medication. In the
presence of cellulitis or any
evidence of bacterial infection,
antibiotics are indicated.
Abscess formation will, of course,
require incision and drainage.
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patellar ligament to the inferior
pole of the patella and this patellar
tendinitis may be associated with
an enlarged infrapatellar bursa.
Treatment of the inflamed bursa
includes prevention of further
mechanical irritation, rest and antiinflammatory medication. In the
presence of cellulitis or any
evidence of bacterial infection,
antibiotics are indicated.
Abscess formation will, of course,
require incision and drainage.
Baker’s cyst
The cyst is the constantly swollen
bursa in relationship to the
semimembranosus tendon and
although it arises in the medial part
of the popliteal fossa, it usually
presents as a central popliteal fossa
mass. The majority of Baker's
cysts appear spontaneously, and
typically persist for 1 or 2 years
before spontaneous resolution.
Exploration and excision are
advisable if the cyst enlarges
rapidly, or if there is any doubt as
to the nature of the lesion.
Avulsion fractures of the lateral
tibial condyle
A lateral tibial condyle avulsion
fracture occurs in severe rotary
strains when the anterior cruciate
ligament is ruptured at the same
time. The avulsion fracture is
called a Segond fracture and was
thought to be pathognomonic of
anterior cruciate ligament rupture
when the telltale flake avulsion was
noted on routine x-ray or MRI.
However, it is now known that it
may also be associated with
posterior cruciate ligament rupture.
Avulsion fractures of the
intercondylar areas
Fractures of the intercondylar areas
in the child are essentially avulsion
fractures of the anterior cruciate
ligament from the tibia. This
fracture is relatively common in the
child but rare in the adult, where
the same injury usually produces a
mid, or lower substance, anterior
cruciate ligament tear.
Group 1 -fractures are minor, distal
and undisplaced.
Group 2 -fracture separation of the
whole tuberosity with displacement
of the fractured segment.
Group 3 -proximal fractures with
major displacement, and
comminution involving also the
upper tibial region.
Conservative treatment is
recommended for fractures with
minimal or no displacement.
All other displaced fractures are
best managed by internal fixation usually with a tension band
technique.
Styloid process - direct blow or
avulsion
LCL if affected instability
May rupture the peroneal nerve or
result in hematoma present around
the nerve may interfere with its
function.
Common fractures of the patella
A stellate type of multifragmental
fracture is usually the result of
falling onto a flexed knee.
Transverse fractures occur when,
with the quadriceps muscle tightly
contracted, a relatively minor blow
to the anterior knee region causes a
transverse break in the patella
separating the superior and inferior
fragments.
The transverse patellar fracture is
most stably fixed by a tension band
wire technique.
Stellate fracture- encircling wires
and fragmentary wire fixation.
Patella trauma
A fracture involving the full
thickness of the patella in a child is
extremely rare. However fractures
of the patellar articular facets are
less uncommon.
Patellar dislocations in children
Lateral - This is by far the most
common variety.
Intercondylar - This is a rare type
of dislocation wherein the patella is
seen to be turned on its side and
fixed in the intercondylar region.
Medial - This is extremely rare, and
when present, is usually iatrogenic.
Lateral patellar dislocation in
children may be either congenital
or acquired.
Osgood-Schlatter’s disease
Etiology of this painful condition,
with a very tender mass developing
at the insertion of the patellar
tendon, is due to a traction avulsion
lesion of the tibial tubercle and
represents an avulsion fracture healing to a degree and then further
being avulsed.