ANATOMY OF THE KNEE JOINT AND POPLITEAL FOSSA

The knee joint is not only the largest and most complex synovial joint in the human body, but also one of the most functionally important — enabling basic movements such as walking, running, sitting, and standing. Its structural complexity makes it prone to injuries, especially in active and aging populations.

We will also examine the popliteal fossa, the diamond-shaped area located behind the knee. While it may seem like a small anatomical space, it holds critical structures such as nerves and vessels that play essential roles in the lower limb’s blood supply and innervation.

1. Knee Joint
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2. introduction
compound joint, consisting of two different
articulation points that combine to form the joint.
primarily a hinge/bicondylarjoint as movement
primarily occurs in one plane (flexion, extension)
but capable of slight rotation and lateral gliding on
knee flexion.
two articulations in the knee are found between
tibia and femur (tibiofemoral)
patella and femur (patellofemoral)
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Patella-femoral joint: patella
form a plane with femur.
joint capsule encloses:
lateral and posterior sides
of patellar ligament
lateral and medial patellar
retinacula.
Ligament are formed by
extensions of the tendon of
the quadriceps femorismuscle

4. Stabilizing factors of knee joint
static (bony, capsular and
ligaments)
Dynamic (muscular and
tendinious)
Dynamic stabilizing of knee
is mainly by;
quadriceps tendon in
front
semimembranosus muscle
tendon on the back
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5. Articular surfaces
distal end of femur and proximal
end of the tibia are both covered
by a layer of hyaline cartilage.
proximal end of the tibia is
covered by C-shaped medial and
lateral meniscus made of
fibrocartilage
connected by a series of
transverse ligament.
function of the menisci:
assist the movement of the
bones over each other,
deepen the tibialplateau
act as a form of shock
absorption.
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6. Clinical relevance of menisci
injury to menisci can occur secondary to sudden twisting of
the knee (e.g. football) which tears the meniscal tissue.
Symptoms: sudden-onset pain, a popping sensation, locking and
instability of the knee joint.
Osteoarthritis:degenerative disease that primarily occurs in
synovial joints involves degeneration of articular surfaces.
Symptoms : joint stiffness, reduced range of joint movement
and joint pain.
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7. extracapsular ligaments
oblique popliteal ligament (an
extension of the tendon of the
semimembranosus hamstring
muscle)
arcuate popliteal ligament
fibular (lateral) collateral ligament
tibial(medial) collateral ligament.
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8. intracapsular ligaments
deep within the joint cavity.
synovial membrane folds around them
but excluded from synovial cavity.
cross each other in the form of an X
and are named according to whether
they attach to the anterior or
posterior side of the tibia :
anterior cruciate ligament (ACL)
posterior cruciate ligament (PCL).
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9. When the knee is extended,
ACL is pulled tight and prevents hyperextension.
PCL prevents the femur from sliding off the front of
the tibia and prevents the tibia from being displaced
backward.
ACL is one of the most common sites of knee injury.
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10. Bipedalism
human bipedalism is the ability to lock the
knees and stand erect without tiring the
extensor muscles of the thigh.
When the knee is extended to the fullest
degree allowed by ACL, femur rotates medially
on tibia.
This action locks the knee and in this state, all
the major knee ligaments are twisted and taut.
To unlock the knee, popliteus muscle rotates
femur laterally, causing the ligaments to
untwist.
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11. Bursae of the knee:
13 in total:
Four are anterior
superficial infrapatellar
suprapatellar
prepatellar
deep infrapatellar.
Located in popliteal region:
popliteal bursa
semimembranosus bursa
more bursae are found on the
lateral and medial sides of the
knee joint.
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12. Blood supply to knee
From the femoral artery: descending
genicular artery branches off superficial
femoral artery.
From the popliteal artery: major source,
giving off several genicular branches that
encircle the knee:
Superior medial and lateral genicular
arteries: Branch from the popliteal artery
above the joint.
Middle genicular artery: Arises from the
popliteal artery at the level of the joint.
Inferior medial and lateral genicular
arteries: Branch from the popliteal artery
below the joint.
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13. Blood supply of the
knee joint
From the anterior tibial
artery: anterior tibial
recurrent artery branches off
to supply knee joint.
Genicular anastomosis:
various genicular branches
form an interconnected
network around the knee
joint and patella, providing a
rich collateral blood supply.
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14. Innervation of the knee joint
branches of the obturator, femoral, tibialand common fibular nerves.
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15. Popliteal fossa
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16. Introduction
rhomboid or diamond shaped
intermuscular space located behind
the knee joint.
Largely filled by fat,
transmits major nerves and blood
vessels between the thigh and the
leg.
It is a region of transition into the
leg.

17. Boundaries
Proximally.
Lateral upper boundary is formed by
biceps femoris
medial upper boundary by the
semitendinosus and semimembranosus.
Distally
lower borders are formed by medial and
lateral heads of the gastrocnemius which
arise from medial and lateral epicondyles
of the femur and converge toward each
other in the calf and plantaris.

18. Popliteal fossa roof
Formed by deep fascia
Pierced by
short saphenous vein
sural nerve
Roof is formed by:
•Skin
•superficial
fascia
•deep fascia of
the thigh and
•popliteal fascia.

19. Popliteal fossa floor
Popliteal surface of femur
Capsule of Knee Jt.
reinforced by oblique
popliteal lig.
Popliteus muscle

21. Popliteal fossa contents
Popliteal Artery
Popliteal Vein
Terminal Branches of Sciatic:
TibialNerve
Common Peroneal (Fibular) Nerve

22. Popliteus muscle
Origin: lateral condyle of the femur by a rounded
tendon and by a few fibers from the lateral semilunar
cartilage.
Insertion:posteriorsurface of tibia above solealline.
Nerve supply: tibialnerve
Action:
medial rotation of the tibia on the femur
lateral rotation of the femur on the tibia if the
foot is on the ground when unlocking the knee
joint .

23. Popliteal artery
It commences at the end of adductor canal and
terminate after it has left the fossa at the
lower border of popliteus muscle.
Genicular Arteries (Knee Supply)
Superior lateral genicular artery
Superior medial genicular artery
Middle genicular artery: (supplies knee joint
capsule and ligaments)
Inferior lateral genicular artery
Inferior medial genicular artery

24. Muscular and Cutaneous Branches
Sural arteries: Provide blood supply to the muscles of the
calf.
Muscular branches: Supply muscles in the posterior thigh and
the leg.
Cutaneous branches: Supply the skin around the knee.
Terminal Branches
Anterior tibialartery: Continues into the anterior
compartment of the lower leg.
Tibioperonealtrunk: short trunk that divides into the
posterior tibialand peroneal (fibular) artery.
Posterior tibialartery: Continues down the posterior part of
the lower leg.
Peroneal (fibular) artery: Runs alongside the posterior tibial
artery.

25. Relationsof popliteal artery
Anterior:
(Floor of the popliteal fossa)
•popliteal surface of the femur
•posterior aspect of the knee
joint
•fascia covering the popliteus
muscle
Posterior:
(from deep to superficial)
popliteal vein
tibialnerve
fascia
skin.

26. Popliteal veinand tributaries
Formed by the union of venae comitantesof
anterior and posterior tibialveins at the lower
border of popliteus muscle.
After adductor hiatus, it becomes femoral
vein.
lies between nerve and artery throughout its
course.
Tributaries
Veins that correspond to the branches given
off by the popliteal artery.
Small saphenous vein.

27. Sciatic nerve
More commonly it divides in the
gluteal region
reaches the popliteal fossa either as
a single nerve where it divides into
the tibialand common fibular nerves
in the upper part of the fossa lying
posterolateral to popliteal vessels.
Common fibular nerve diverges
laterally to pass around the lateral
side of the leg,
tibia nerve descends almost straight
down through the fossa.

28. Tibialnerve
It is the larger terminal of sciatic nerve.
Where it starts varies.
nerve enters the posterior compartment of the
leg by passing beneath the soleus muscle.
Branches
Sural nerve descends between the two heads of
gastrocnemius muscle and is usually joined by
sural communicating branch of the common
peroneal nerve. It accompanies small saphenous
vein behind lateral malleous.
Muscular and articular branches.

29. Common fibular (peroneal) nerve
It runs down the fossa closely following the medial
border of the biceps muscle.
It leaves the fossa by crossing superficially the lateral
head of gastrocnemius muscle.
It then passes behind head of fibula.

30. Fibular nerve
winds laterally around the neck of the bone,
pierces the peroneus longus muscle, and
divides into two terminal branches:
Superficial peroneal nerves
deep peroneal nerves.
It is subcutaneous at the lateral aspect of the
neck of the fibula.
Branches: Sural communicating, lateral
cutaneous nerve of the calf, muscular and
articular.

31. Obturator nerve
It leaves the adductor canal with
the femoral artery and terminates
by supplying the knee joint.

32. Popliteal lymph nodes
These few lymph nodes
receive both superficial
lymph vessels
accompanying small
saphenous vein and deep
lymphatics accompanying
the anterior and posterior
tibialarteries.

33. Thank you
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