Popliteal Fossa -contents,Borders, clinical anatomy

The popliteal fossa is a diamond-shaped depression. Situated behind the knee joint, the lower part of the femur,and the upper part of the tibia.

Boundaries of popliteal fossa

Superalaterally : The biceps femoris.

Superalaterally : The semitendinosus and the semi-
membranosus, supplemented by the gracilis, the
sartorius and the adductor magnus.

Inferolaterally : Lateral head of the gastrocnemius
supplemented by the plantaris.
Inferomedially : Medial head of the gastrocnemius.
The roof of the fossa is formed by deep fascia or
popliteal fascia. The superficial fascia over the
roof contains –

a. The small saphenous vein and cutaneous nerves.
b. Three cutaneous nerves, namely, the branches and End part of the posterior cutaneous nerve of
the thigh, the posterior division of the medial
cutaneous nerve of the thigh, and the peroneal or
sural communicating nerve.

The floor of the popliteal fossa is formed from above downwards by –

a. The popliteal surface of the femur.
b. The capsule of the knee joint and the oblique
popliteal ligament.
c. The strong popliteal fascia covering the popliteus
muscle

Popliteal Fossa-contents|Borders|clinical anatomy

Contents –

1. The popliteal artery and its branches
2. The popliteal vein and its tributaries.
3. The tibial nerve and its branches.
4. The comnon peroneal nerve and its branches.
5. The posterior cutaneous nerve of the thigh.
5. The genicular branch of the obturator nerve.
7. The popliteal lymph nodes.
8 Fat.

The popliteal vessels & the tibial nerve cross the
fossa vertically, and are arranged one over the other. The tibial nerve is most superficial; the popliteal vein lies deep or anterior to tibial nerve; and the popliteal artery is deepest of all. The artery is crossed dorsally by the vein and by the nerve. The relative position of these structures is as follows.

In the upper part of the fossa, from medial to lateral side: artery, vein and nerve (A, V, N).
In the middle part, from behind forwards:nerve, vein and artery (N, V, A).
In the lower part, from medial to lateral side: nerve, vein and artery (N, V, A).

Popliteal artery –

Beginning, course and termination

Popliteal artery is the continuance of the femoral artery. It begins at the opening in the adductor magnus or hiatus magnus, i.e. at the junction of middle one-third with the lower one-third of thigh.
It runs downwards and slightly laterally, to reach
the lower border of the popliteus.
It terminates at the lower border of popliteus by
Splitting into the anterior and posterior tibial arteries.

Relations
The popliteal artery is the deepest formation in the
popliteal fossa. It has the following relations. deep to the artery, from above downwards, there are:
• The popliteal surface of the femur.
• The back of the knee joint.
• The fascia covering the popliteus muscle.

Posterior or superficially: To the tibial nerve

Laterally: Biceps femoris and the lateral condyle of the femur in the upper part, plantaris and the lateral head of the gastrocnemius in the lower part.

Medially: Semimembranosus and the medial condyle of the femur in the upper part. The lower part of the artery is related to the tibial nerve, the popliteal vein, and the medial head of the gastrocnemius in the lower part.

Branches of popliteal artery –

Several large muscular branches are given off. The upper (two or three) muscular branches supply the adductor magnus and the hamstrings, and terminate by anastomosing with the fourth perforating artery. The lower muscular or sural branches supply the gastrocnemius, the soleus and the plantaris.

Cutaneous branches arise either directly from the
popliteal artery, or indirectly from its muscular
branches. One cutaneous branch usually accompanies the small saphenous vein.

Genicular branches are five in number, two inferior, two superior & one middle. The middle genicular artery pierces the oblique popliteal ligament of the knee, and supplies the cruciate ligaments and the synovial membrane of the knee joint.
The medial and lateral superior genicular arteries wind round the corresponding sides of the femur
immediately above the corresponding condyle, and
pass deep to the hamstrings.
The medial and lateral inferior genicular arteries wind round the corresponding tibial condyles, and pass deep to the collateral ligaments of the knee. All these arteries reach the front of the knee and take part in forming the anastomoses around the knee. Popliteal Fossa-contents|Borders|clinical anatomy

Popliteal vein –

The popliteal vein begins at the lower border of the popliteus by the union of veins accompanying the anterior and posterior tibial arteries. It is medial to the popliteal artery in the lower part of the fossa; dorsal to the artery in the middle; and posterolateral to it in the upper part of the fossa. The popliteal vein continues as the femoral vein at the opening in the adductor magnus. The popliteal vein receives:
1 The small saphenous vein.
2 The veins corresponding to the branches of the
popliteal artery.

Popliteal Fossa-contents|Borders|clinical anatomy

Popliteal Fossa-contents|Borders|clinical anatomy

Tibial nerve

Raot value of tibial nerve : Ventral divisions of ventral rami of L4, L5,51, 52, 53.

Course
This is the larger terminal branch of the sciatic nerve. It lies dorsally or superficial to the popliteal vessels. It elongates from the superior angle to the inferior angle of the popliteal fossa, crossing the popliteal vessels from lateral to medial side. Popliteal Fossa-contents|Borders|clinical anatomy

Branches of Tibial nerve

1. Three genicular or articular branches arise in the upper part of the fossa these are:
a. Superior medial genicular nerve lies above the medial condyle of femur, deep to the muscles.
b. Middle genicular nerve pierces the posterior part of the capsule of the knee joint to supply structures in the intercondylar notch of femur.
c. Inferior medial genicular nerve lies along the upper border of popliteus and reaches inferior to the medial condyle of tibia.

2. Cutaneous nerve is called sural which originates in the middle of the fossa and leaves it at the inferior angle. It supplies the skin of lower half of back of leg and whole of lateral border of the foot till the tip of little toe.
3 Muscular branches arise in the distal part of the fossa for the lateral and medial heads of gastrocnemius, soleus, plantaris and popliteus.

The nerve to the popliteus crosses the popliteal artery, runs downwards and laterally, winds round the lower border of the popliteus, and supplies it from its deep (anterior) surface. In addition to the popliteus, the nerve also supplies the tibialis posterior, the superior tibiofibular join the tibia, the interosseous membrane, and the inferior tibiofibular joint.

• Related – How to study physiology in medical school

otic ganglion

Clinical anatomy –

• Blood pressure in the lower limb is recorded from
the popliteal artery. In coarctation of the aorta, the
popliteal pressure is lower than the brachial
pressure.

• Constant pulsations of the popliteal artery against
the unyielding tendon of the adductor magnus
may cause changes in the vessel wall, leading to
narrowing and occlusion of the artery. Sudden
occlusion of the artery may cause gangrene up to
the knee, but this is usually prevented by the
collateral circulation through the profunda
femoris artery.

• The popliteal artery is fixed to the capsule of the
knee joint by a fibrous band present just above
the femoral condyles. This may be a source of
continuous traction or stretching on the artery,
causing primary thrombosis of the artery in young
subjects.

• When the popliteal artery is affected by
atherosclerosis, the lower part of artery usually
remains patent where grafts can be tried.

• The popliteal artery is more prone to aneurysm
than many other arteries of the body.