- The Knee Joint is the largest.
- Most complicated joint in the body.
- Most superficial joint.
- Hinge type of synovial joint.
knee is essentially made up of three bones
It consists of 3 Joints within a single synovial cavity :
- Medial Condylar Joint : Between the medial condyle
“of the femur” & the medial condyle “of the tibia” .
- Lateral Condylar Joint : Between the lateral condyle
“of the femur” & the lateral condyle “of the tibia” .
- Patellofemoral Joint : Between the patella & the
patellar surface of the femur .
Articulation , Articular surfaces , and
stability of the knee joint
The articulating surfaces of the knee
joint are characterized by their large
size and their complicated and
incongruent shape. The knee joint
consists of three articulation:
- Two femorotibial articulation ( lateral
and medial ) between the lateral and
the medial femoral and tidial condyles.
- One intermediate femoropatellar
articulation between the patella and
- The fibula is not involved in the knee
The stability of the knee joint
depends on :
1- the strength and the action of the
surrounding muscles and their
2- the ligaments that connect the
femur and tibia.
Of these supports, the muscles are most
important therefore many sport injuries
are preventable through appropriate
conditioning and trainig. The most
important muscle in stabilizing the knee
joint is the large quadriceps femoris
particularly the inferior fibers of the
vastus medialis and lateralis.
A joint capsule is a piece of tissue that surrounds a synovial joint. Its
purpose is to hold the synovial fluid of the joint in place, as well as
to provide an envelope for the entire joint. The capsule provides an
important function to all synovial joints, but it can cause problems,
such as frozen shoulder, osteoarthritis, and inflamed plica
syndrome, when not functioning properly.
The most common type of joint in the human body is the synovial
joint, which contains fluid that helps to lubricate movement.
Fibrous joints do not contain either synovial fluid or a joint capsule.
Joints containing this fluid can perform a number of different
actions, including abduction, extension, and rotation.
Synovial joints appear in the body in a number of different forms. For
example, the elbow is a simple hinge joint, while the hip is a more
complicated ball-and-socket joint that allows a greater range of
movement. Joint capsules are present in all of these joints.
The capsule is made up of two separate layers. The first is an outer
layer that contains a fibrous, colorless tissue. The second, inner
layer is often called the synovial membrane. Both of these layers
need to be in a healthy state in order for the joint to move as it
The knee joint capsule allows the full knee to have flexion, or
bending, motion due to the folds in the capsule. The joint capsule is
made up of the patella, which is within the anterior capsule, as well
as the tibia and the femur. The patella is also known as the kneecap.
The capsule is held together with ligaments that help with the range
of motion. The capsule has synovial fluid, or fluid found in the
cavities of synovial joints, that will circulate around the patella,
tibia, and femur. Its posterior aspect, or back part of the structure,
is stronger and thicker. It makes the person, when standing, more
stable and able to balance. The knee joint capsule provides static
stabilization for the knee, which is unstable due to its bony
configuration. The knee joint itself has two nearly flat surface bones.
These surface bones lie on one another as a primary articulating
surface. It is the capsule that provides the knee joint its movement.
Extracapsular Ligament of knee joint
1- Patellar Ligament
- the distal part of the quadriceps tendon.
- thick fibrous band.
- is the anterior ligament of knee joint.
- Laterally, it receives the medial and lateral patellar retinacula, aponeurotic
expansion of the vastus medialis and lateralis and overlying deep fascia.
2- Fibular collateral ligament
- Extends inferiorly from the lateral epicondyle of the femur to the lateral surface
of the fibular head
3- Tibial collateral ligament
- Extends from the medial epicondyle of the femur to the medial condyle and the
superior part of the medial surface of the tibia
4- Oblique popliteal ligament:
- recurrent expansion of the tendon of the semimembranosus.
- it arises posterior to the medial tibial condyle.
- passes superolaterally toward the lateral femoral condyle.
- with the central part of posterior aspect of the joint capsule.
5- The Arcuate Popliteal Ligament:
- strengthens the joint capsule posterolaterally.
- It arises from the posterior aspect of the fibular head, passes
superomedially over the tendon of the popliteus , and spreads over the
posterior surface of the knee joint.
- Its development is related to the presence and size of a fabella in the
proximal attachment of the lateral head of gastrocnemius.
- Both structures are thought to contribute to stability of the knee.
Intra-Articular ligaments Cruciate
The anterior cruciate ligament:
- the weaker of the two cruciate ligaments .
- arise from the anterior intercondylar area of the tibia ,
just posterior to the attachment of the medial meniscus .
- the ACL has a relatively poor blood supply.
- it extends superiorly , posteriorly and laterally to attach to
the posterior part of the medial side of the lateral condyle
of the femur
- it also prevents posterior displacement of the femur of the
tibia and hyperextension of the knee joint .
The posterior cruciate ligament :
- the stronger of the two cruciate ligaments.
- arises from the posterior intercondylar area of the tibia
- the PCL passes superiorly and anteriorly on the medial
side of the ACL to attach to the anterior part of the lateral
surface of the medial condylar of the femur
- the PCL limits anterior rolling of the femur on the tibia
plateau during extension converting it to spin.
- it also prevents anterior displacement of the femur on the
tibia or posterior displacement of the tibia on the femur
and helps prevent hyperflexion of the knee joint.
Menisci Of Knee Joint
The knee joint is the most complex and remarkable
joint in the body.
The knee’s menisci are two half-moon, wedge shaped
pieces of cartilage (the lateral and medial
meniscus), acting as lubricant and elastic
buffer, distributing forces evenly between the femur
(upper leg) and tibia (lower leg) in the knee joint.
- Their attachment to the intercondylar area of the tibia and
tibia attachments of the cruciate ligaments.
- The BAND like tibial collateral ligament is attached to the
- The CORD like fibular collateral ligament is sparated from
- The posterior meniscofemoral ligament attaches the latreral
- Flexion and Extension are the MAIN knee movement.
Blood supply of the knee joint
The Femoral artery and the popliteal artery forms artery
network surrounding the knee joint ,
There are 6 main branches :
1. Superior medial genicular artery
2. Superior lateral genicular artery
3. Inferior medial genicular artery
4. Inferior lateral genicular artery
5. Descending genicular artery branch from the femoral artery
6. Recurrent branch of anterior tibial artery
The medial genicular arteries penetrate the knee joint
Innervation of the knee
The nerves around the knee are motor (move muscles) and
sensory (allow you to feel what is happening). The sensory
nerves supply the joint itself as well as the skin over the
knee. Many muscles have both motor and sensory functions.
While there is a great deal of variation in the nerves, essentially
there are the nerves at the back of the knee and the nerves at the
front of the knee. The nerves that supply sensation to the back of
the knee joint itself are the posterior (back) articular (joint)
branches of the tibial and obturator nerves. The equivalent
nerves in the front are the articular branches of the femoral,
common peroneal and saphenous nerves. This is different to the
pattern of skin sensation nerve supply
(L2,3,4) supplies the adductor muscles on the inner side
of the thigh. These are the muscles that squeeze the knees
together. This nerve also supplies the hip and sometimes
pain from the hip can be felt as pain on the inner side of
the knee. For this reason the hip must always be examined
if the cause of the pain in the knee is not obvious.
The femoral nerve (L2,3,4) supplies the main muscles at
the front of the thigh (motor) as well as the knee joint
(sensory). Damage to the femoral nerve results in
weakness of the quadriceps muscles (which straighten the
knee). The saphenous nerve is a sensory continuation of
the femoral nerve (supplies feeling to the inner aspect of
The femoral nerve (L2,3,4) supplies the main
muscles at the front of the thigh (motor) as well as
the knee joint (sensory). Damage to the femoral
nerve results in weakness of the quadriceps muscles
(which straighten the knee). The saphenous nerve is
a sensory continuation of the femoral nerve (supplies
feeling to the inner aspect of the foot).
The sciatic nerve
(L4,5, S1,2,3) is a large nerve which runs down the
back of the leg. It is made up of the tibial and
common peroneal nerves which branch at different
levels of the leg in different people. The sciatic nerve
splits into the tibial and common peroneal nerves
above the knee. The tibial nerve supplies the
hamstring muscles (which bend the knee). It also
supplies the muscles in the back if the calf
(gastrocnemius and soleus). The common peroneal
nerve supplies the front compartments of the leg
including the peroneal muscles.
The tibia nerve
is the larger of the two branches of the sciatic nerve and
runs down the back of the knee. The common peroneal
nerve separates from the tibial portion of the sciatic nerve
just above the knee and then follows behind the hamstring
on the outer side of the leg to top part of the smaller done
in the leg called the fibula. The nerve then goes past the
head of the fibula, winds round the neck of the fibula and
dives deep into the muscles to divide into the superficial
(closer to the surface) and deep (further inside) peroneal
Any nerve that goes past the knee joint gives off a
sensory branch to the knee joint.
Nerve injury around the knee is rare compared to
meniscal, chondral or ligamentous injuries. Nerve releases
are occasionally needed but are rare compared to
arthroscopic and reconstructive surgery of the knee
Common peroneal nerve
The common peroneal nerve is one of two major
branches of the sciatic nerves within the buttocks
and into the thighs, along with the tibial nerves.
The many branches of these nerves supply nerve
impulses to and from the muscles and skin in the
hip joints and thighs, the lower legs, feet and
most of the skin below the knee.
The saphenous nerve long branch of femral nerve, about the
middle of the thigh, gives off a branch which joins the
At the medial side of the knee it gives off a large infrabatellar
branch , which pierces the Sartorius and fascia lata, and is
distributed to the skin in front of the patella.
Below the knee, the branches of the saphenous nerve
(medial crural cutaneous branches) are distributed to the
skin of the front and medial side of the leg, communicating
with the cutaneous branches of the femoral, or with
filaments from the obturator nerve.
Between femur & tendon
Held in position by
of quadriceps femoris ..
articular genu muscles;
Between tendon of
Opens into freely with
(superior extension of)
Popliteus & lateral
cavity of knee joint
synovial cavity of knee
condyle of tibia
inferior to lateral
Separates tendons. of
Area where tendons of
Sartorius, gracilis &
these muscles attach to
the tibia; resembles
Deep to proximal
An extension of synovial
tibia & tibial tendon of
goose’s foot .
cavity of knee joint .
medial head of
Between medial .head of
Related to distal
Between skin & anterior Allows free movement. of
surface of patella .
skin over patella during
movements of leg .
Between skin & tibial
Helps knee withstand
pressure when kneeling .
Separated from knee
ligament & anterior
joint by infrapatellar fat
surface of tibia .
Applied Genu Varum &
The femur is placed diagonally within
the thigh. whereas the tibia is almost
vertical within the leg, creating an
angle, the Q-angle, at the knee
between the long axes of the bones.
The Q-angle is assessed by drawing a
line from the ASIS to the middle of
the patella and extrapolating a
second (vertical) line through the
middle of the patella and tibial
The Q-angle is typically greater in
adult females, owing to their wider
pelves. A medial angulation of the leg
in relation to the thigh, in which the
femur is abnormally vertical and the
Q-angle is small, is a deformity called
genu varum (bowleg) that causes
Excess pressure is placed on the
medial aspect of the knee joint,
which results in arthrosis
(destruction of knee cartilage).
A lateral angulation of the leg in relation
to the thigh (exaggeration of knee angle)
is genu valgum
Consequently, in genu valgum, excess
stress is placed on the lateral
structures of the knee. The patella,
normally pulled laterally by the tendon
of the vastus lateralis, is pulled even
farther laterally when the leg is
extended in the presence of genu
varum so that its articulation with the
femur is abnormal.
- patella is dislocated, it nearly always dislocation laterally.
- most common in women.
- the tendency toward lateral dislocation is normally
counterbalanced by the medial, more horizontal pull of
powerful vastus medialis.
- in addition, the more anterior projection of the lateral femoral
condoyle and deeper slope for the large lateral patellar facet
provide a mechanical deterrent to lateral dislocation.
- imbalance of the lateral pull and mechanisms resisting it result
in abnormal tracking of the patella within the patellar groove
and chronic patellar pain, even if actual dislocation does not
Pain deep to the patella often results
from excessive running , especially
- This type of pain is often called
- The pain results from repetitive
microtrauma caused by abnormal
tracking of the patella relative to the
patellar surface of the femur, a
condition know as the patellofemoral
In some cases , strengthening of the vastus medialis corrects
This muscle tends to prevent lateral dislocation of the patella
resulting from the Q angle because the vastus medialis
attaches to and pulls on the medial border of the patella .
Hence, weakness of the vastus medialis predisposes the
individual to the patellofemoral dysfunction and patellar
Knee joint injury
- common(low placed, mobile, weight bearing and serving
as fulcrum bet 2 levers.
- Stability depends on the associated ligament and
- it’s essential for everyday activities (stand ,walk..&
climbing stairs) and considers main joint for sports( jump,
run and change direction).
- Knee is susceptible to injuries because is mobile.
- Common injuries in contact
sports are(ligament sprains).
(when the foot fixed in ground,
if force is applied against knee,
when foot cannot move.
- (TCL) & (FCL) are tightly
stretched when .. & preventing
disruption the knee from sides.
- (TCL) attachment to
- Injury is frequently caused by a blow to lateral
side of extended knee or excessive lateral
twisting of flexed knee , (TCL) may be andor
from joint capsule , this common in athletes.
- (ACL) anterior cruciate ligament,
it’s serves as axis for rotatory
movement knee, is taut during flexion,
may also tear subsequent to
rupture of (TCL) creating
“unhappy triad” .
Your thigh bone (femur) and lower leg bones (tibia and fibula) meet
in the knee joint and are held together by tissue called ligaments. In
the middle of the knee are two ligaments called the
- anterior (front) cruciate ligament (ACL)
- posterior (back) cruciate ligament (PCL)
BASIC of (ACL)
Function of (ACL)
- prevents the tibia
from slipping forward
against the femur.
- prevents the femur
from moving too far
backward over the tibia
Injury to the ACL
This injury causes the free tibia to slide anteriorly
under the fixed femur, known as the anterior
BASIC of (PCL)
Function of (PCL)
- prevents the femur
from moving too far
forward over the tibia.
- knee’s basic stabilizer
and is almost twice as
strong as the ACL
Posterior view of the
Injury to the PCL
This injury allow the free tibia to slide posteriorly
under the fixed femur, known as the posterior
Most athletic PCL injuries occur during a fall on the flexed (bent) knee
with the foot plantar flexed (the toes pointing down with the top of the
foot in line with the front of the leg). The shin (tibia) strikes the
ground first and is pushed backward
Is endoscopic examination that allow visualization of •
the interior of the knee joint cavity with minimal
disruption of tissue .
Portals : arthroscope and one or more additional •
canula are inserted through tiny incisions .
* The scenod canula is for passage of specialized tools (
e.h, manipulative forceps ) or equipment for trimming ,
shaping , removel damage tissue .
* In knee arthroscopy can using local or
regional anesthesia .
* this technique allows removal of torn
menisci , loose bodies in the joint
, debridement in advanced case of
arthitis ligment repair or replacement .
* Druing arthroscopy , the articular
cavity of the knee must be treated
essentially as two separate ( medial and
lateral ) femorotibial articulation owing
to the imposition of synovial fold around
the cruciate ligment .
Aspiration Of Knee Joint
Fractures (distal end of
( Inflammation )
Lacerations of the anterior thigh
( involve suprapatellar bursa )
Performing Direct Aspiration of the knee joint:
- Patient setting ( table).
- knee flexed.
- Joint should be approached laterally.
- Three bony point as Landmarks for needle insertion
(+drug injection )
1- Apex of patella
2- Lateral epicondyle of femur
3- anterolateral tiblial (Gerdy) tubercle.
Bursitis in the knee region
Bursitis : is a painful condition that affects the small fluid-filled pads called
bursae. that act as Facilitate the movement between bones and the tendons
and muscles near of the joints .
There are three bursas in the knee region : prepatellar- inrfapatellar( is
divided into deep and superficial)- suprapatellar .
Caused by friction between
the skin and patella ,
and may be injured by
compressive forces resulting
frome direct blow or from
falling on the flexed knee .
If the inflammation is chronic, the bursa become distended with fluid and
forms a swelling anterior to the knee.
Is caused by
between the skin
and the tebia
Deep infrapatellar :
Results in edema between the patellar
ligament and the tibia, superior to the tibial
The inflammation is usually caused by
overuse and subsequent friction between
the patellar tendon and the structures
posterior to it.
The Structures posterior of the tendon is:
The infrapatellar fat pad and tibial .
Penetrating wounds may result in suprapatellar
bursitis, an infection caused by bacteria entering
the bursa frome the torn skin.
The infection may spread
to the cavity of the knee
joint, causing localized
redness and enlarged
popliteal and inguinal
are abnormal fluid filled sacs of synovial
membrane in the region of the popliteal
popliteal cyst is almost always a
complication of chronic knee joint
The cyst may be a herniation of the gastrocnemius or
semimembranosus bursa through the fibrous layer of
the joint capsule into the popliteal fossa .
Communicating with the synovial cavity of knee joint
by a narrow stalk .
Synovial fluid may also escape from knee joint or a
bursa around the knee and collect in the popliteal
Here it forms a new synovial-lined sac ,or popliteal
Popliteal cyst are common in children but seldom
cause symptoms .
In adults , popliteal cysts can be large , extending as
far as the midcalf , and may interfere with knee
Knee replacement, or knee arthroplasty, is a surgical
procedure to replace the weight-bearing surfaces of the
knee joint to relieve pain and disability.
a. Knee replacement surgery is most commonly performed
in people with advanced osteoarthritis and should be
considered when conservative treatments have been
b. Total knee replacement is also an option to correct
significant knee joint or bone trauma in young patients.
c. Similarly, total knee replacement can be performed to
correct mild valgus or varus deformity.
a. The most serious complication is infection of the
joint, which occurs in <1% of patients.
Deep vein thrombosis occurs in up to 15% of
patients, and is symptomatic in 2–3%.
Nerve injuries occur in 1–2% of patients.
Persistent pain or stiffness occurs in 8–23% of patients.
Prosthesis failure occurs in approximately 2% of
patients at 5 years.