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The popliteal fossa is a shallow, diamond-shaped depression at the back of the knee joint, best felt when the joint is semi-flexed.
It corresponds to the cubital fossa of the upper limb.
It serves as a major passage for neurovascular structures between the thigh and leg
Volume 2, BD Chaurasia’s Human …
.Lateral and medial condyles of femur and tibia can be palpated on the sides and front of the knee.
Head of fibula — prominent bony point just below the posterolateral tibial condyle.
Common peroneal nerve — palpable against the neck of fibula, medial to the tendon of biceps femoris.
Fibular collateral ligament — feels like a rounded cord above fibular head when the knee is flexed.
Tendons around knee:
Medially: rounded semitendinosus over flat semimembranosus, with adductor magnus anteriorly.
Laterally: biceps femoris tendon anterior to iliotibial tract.
Popliteal artery pulsation — felt deep in the mid-fossa.
Two heads of gastrocnemius form the lower boundaries merging into the calf
Volume 2, BD Chaurasia’s Human …
.Make horizontal incisions: one across the back of the thigh (upper 2/3 junction) and one across the back of the leg (lower 1/3 junction).
Connect with a vertical midline incision; reflect the skin and fascia.
Identify cutaneous nerves (posterior cutaneous nerve of thigh, medial cutaneous nerve, sural nerve) and short saphenous vein.
Clean the deep fascia to expose the boundaries and contents.
Trace:
Tibial nerve in the midline (gives articular, cutaneous, and muscular branches).
Common peroneal nerve medial to biceps femoris.
Popliteal vein deep to tibial nerve and popliteal artery as the deepest structure
Volume 2, BD Chaurasia’s Human …
.Lies posterior to the knee joint, between the lower femur and upper tibia, forming a diamond-shaped hollow
Volume 2, BD Chaurasia’s Human …
.Superolateral → Biceps femoris
Superomedial → Semitendinosus and semimembranosus (with sartorius, gracilis, adductor magnus).
Inferolateral → Lateral head of gastrocnemius and plantaris.
Inferomedial → Medial head of gastrocnemius.
Roof:
Formed by deep fascia (popliteal fascia).
Superficial fascia contains the small saphenous vein, posterior cutaneous nerve of thigh, medial cutaneous nerve branches, and sural communicating nerve.
Floor:
From above downwards:
Popliteal surface of femur
Posterior capsule of knee joint
Oblique popliteal ligament
Popliteus fascia and muscle
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.Popliteal artery and its branches.
Popliteal vein and its tributaries.
Tibial nerve and its branches.
Common peroneal nerve and branches.
Posterior cutaneous nerve of thigh.
Genicular branch of obturator nerve.
Popliteal lymph nodes and fat surrounding all structures.
Arrangement (superficial to deep):
Tibial nerve (most superficial)
Popliteal vein (middle)
Popliteal artery (deepest)
In the upper part: medial to lateral → Artery, Vein, Nerve (A-V-N)
Middle part: posterior to anterior → Nerve, Vein, Artery (N-V-A)
Lower part: medial to lateral → Nerve, Vein, Artery (N-V-A)
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Continuation of the femoral artery beyond the adductor hiatus.
Lies deepest in the fossa.
Ends at the lower border of popliteus, dividing into anterior and posterior tibial arteries.
Relations:
Anterior: popliteal surface of femur, knee capsule, popliteus fascia.
Posterior: popliteal vein, tibial nerve.
Medial: semimembranosus and medial condyle.
Lateral: biceps femoris, plantaris, lateral head of gastrocnemius.
Branches:
Muscular (to hamstrings and gastrocnemius)
Cutaneous
Genicular (superior, inferior, and middle) — form the genicular anastomosis around the knee
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.Blood pressure of the lower limb is recorded from the popliteal artery.
In coarctation of aorta, popliteal pressure is lower than brachial.
The popliteal artery is prone to aneurysm due to its fixed position against the femur.
Pulsations may compress the tendon of adductor magnus, causing arterial narrowing.
Collateral circulation through profunda femoris prevents gangrene if occlusion occurs.
The popliteal vein receives the small saphenous vein and may develop deep vein thrombosis (DVT).
Tibial nerve can be compressed in popliteal entrapment syndrome
.
Origin: At the lower border of the popliteus by the union of the anterior and posterior tibial veins.
Course:
Lies medial to the popliteal artery in the lower part.
Lies posterior to the artery in the middle part.
Lies posterolateral to the artery in the upper part.
Termination: Continues as the femoral vein at the opening of adductor magnus.
Tributaries:
Small saphenous vein (chief tributary).
Veins corresponding to branches of the popliteal artery.
Clinical Note: May become dilated in deep vein thrombosis (DVT); inflammation here can cause calf pain and swelling
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.Root value: Ventral divisions of ventral rami of L4, L5, S1, S2, S3.
Origin: Larger terminal branch of the sciatic nerve.
Course: Lies superficial to popliteal vessels, extending from the superior angle to the lower border of popliteus.
Branches:
Muscular: To gastrocnemius, soleus, plantaris, and popliteus.
Cutaneous: Medial sural cutaneous nerve (joins lateral sural branch → sural nerve).
Articular: 3 branches to the knee joint.
Clinical Note: Compression in popliteal entrapment syndrome may cause weakness of plantar flexion or sole sensation loss
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.Root value: Dorsal divisions of ventral rami L4, L5, S1, S2.
Course:
Descends along medial border of biceps femoris.
Winds around neck of fibula, lying subcutaneously and very vulnerable to injury.
Branches:
Lateral sural cutaneous nerve (cutaneous).
Communicating branch to sural nerve.
Deep and superficial peroneal nerves (terminal branches).
Clinical Note:
Most frequently injured nerve in the lower limb.
Injury at fibular neck causes foot drop (loss of dorsiflexion and eversion).
Sensory loss over the lateral leg and dorsum of foot
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.Origin: From the sacral plexus (S1–S3).
Course:
Enters fossa superficial to hamstring tendons.
Gives inferior cluneal (to buttock) and perineal branches.
Supplies skin over posterior thigh and popliteal region.
Clinical Note: May be stretched or compressed in prolonged sitting, causing posterior thigh tingling.
Origin: From the posterior division of obturator nerve.
Course:
Crosses popliteal artery to reach the posterior capsule of knee joint.
Communicates with tibial articular branches.
Function: Sensory supply to posterior knee joint capsule and cruciate ligaments.
Number: Usually 6 or 7.
Location: Along the small saphenous vein and popliteal vessels within the fat of the fossa.
Afferents:
From lateral side of foot, heel, and posterior leg.
Efferents:
Drain into the deep inguinal lymph nodes.
Clinical Note:
Enlarged in infections or ulcers on the lateral side of the foot or posterior leg.
Palpable behind the knee when inflamed (“popliteal lymphadenitis”)
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.Popliteal Vein Thrombosis: Causes calf tenderness, swelling, and risk of pulmonary embolism.
Common Peroneal Nerve Injury: Leads to painless foot drop, weakness of dorsiflexion and eversion, with normal inversion and plantar flexion.
Tibial Nerve Lesion: Loss of plantar flexion and sole sensation.
Enlarged Popliteal Lymph Nodes: Occur in lateral foot infections; lymph drains along short saphenous vein to popliteal nodes
The knee joint is richly supplied by a genicular arterial network formed mainly by branches of the popliteal artery, with contributions from the femoral, profunda femoris, and anterior tibial arteries.
These anastomoses ensure continuous blood flow during knee movements and provide collateral circulation when the femoral or popliteal artery is compressed or ligated.
This is a rich vascular plexus surrounding the front and sides of the knee joint.
Formed by:
From Popliteal Artery:
Superior medial genicular artery
Superior lateral genicular artery
Inferior medial genicular artery
Inferior lateral genicular artery
Middle genicular artery (pierces the capsule; does not take part in surface anastomosis)
From Descending Branches of Femoral and Profunda Femoris Arteries:
Descending genicular artery (from femoral artery).
Descending branch of lateral circumflex femoral artery (from profunda femoris).
From Below:
Anterior tibial recurrent artery (from anterior tibial artery).
Posterior tibial recurrent artery (from posterior tibial artery).
Around the Patella:
The genicular branches form the patellar network, lying in the superficial fascia around the patella and ligamentum patellae.
Around the Femoral and Tibial Condyles:
The superior and inferior genicular arteries interconnect along the medial and lateral borders of the joint.
Within the Joint:
The middle genicular artery pierces the posterior capsule to supply the cruciate ligaments and synovial membrane.
The genicular network below continues upward with the cruciate anastomosis (in upper thigh) and downward with recurrent tibial arteries — forming a complete collateral channel between the femoral and tibial systems.
Collateral Circulation:
When the femoral artery is ligated above the adductor hiatus, blood still reaches the popliteal artery via:
Descending branch of lateral circumflex femoral
Descending genicular
Genicular branches of popliteal artery
Aneurysm:
The popliteal artery’s fixed position behind the knee makes it prone to aneurysm; the genicular network helps maintain distal perfusion if the main artery is compressed.
Palpation Site:
The popliteal artery pulsation can be felt deep in the fossa while the knee is flexed.
“Four Poplites Descend Anteriorly” →
Four = 4 genicular branches of popliteal artery (2 superior, 2 inferior)
Poplites = Popliteal artery (main source)
Descend = Descending genicular (from femoral) and Descending branch of lateral circumflex femoral
Anteriorly = Anterior and posterior tibial recurrent arteries
Total six main arteries form the external anastomotic ring:
Superior medial genicular
Superior lateral genicular
Inferior medial genicular
Inferior lateral genicular
Descending genicular (femoral)
Descending branch of lateral circumflex femoral
The middle genicular is deep and supplies intra-articular structures.
This network maintains blood supply to the leg even when knee flexion compresses the popliteal artery.
To remember the arrangement of artery (A), vein (V), and nerve (N) in different parts of the fossa:
Upper part (medial to lateral):
A V N → Artery, Vein, Nerve
Middle part (posterior to anterior):
N V A → Nerve, Vein, Artery
Lower part (medial to lateral):
N V A → Nerve, Vein, Artery
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