POPLITEAL FOSSA
LEARNING OBJECTIVES
n To understand the boundaries of popliteal fossa.
n To discuss the contents of the popliteal fossa.
n To know some clinical correlates regarding popliteal fossa.
POPLITEAL FOSSA
· Diamond shape intra muscular space at the back of thigh
· More prominent when knee joint is flexed
BONES OF POPLITEAL FOSSA
• The bones of the popliteal fossa are:
• Femur
– medial condyle
– lateral condyle
• Tibia
– medial condyle
– lateral condyle
BOUNDARIES
n Superolateral- biceps femoris
n Superomedial - semimembranosis and semitendinosus
n Inferolateral – medial head of the gastrocnemius
n Inferomedial -lateral head of gastrocnemius
n Posterior wall or roof - skin & popliteal fascia
n Anterior wall or floor– popliteal surface of the femur, the medial & lateral supracondylar lines, posterior capsule of the knee joint, popliteus fascia covering the popliteus muscle forms the floor of the fossa.
MUSCLES INVOLVED IN POPLITEAL FOSSA
Muscles of hamstring group:
1. Semimembranosus
2. Semitendinosus
3. Biceps femoris
· Arise from ischial tuberosity in addition short head of bicep femoris arise from lateral supracondylar ridge of femur and linea aspera
· Insertion:
Bicep to head of fibula, semimembranosus and semitendinosus from tibia
· Nerve supply: tibial portion of sciatic ; short head of bicep from common fibular portion of sciatic
Muscles of posterior compartment of leg
Gastrocnemius lateral and medial head
· Arise from lateral and medial condyle of femur respectively
· Inserted into calcaneium
· Nerve supply tibial nerve
· Action plantar flexion of ankle, flexor of knee
Muscle of popliteal fossa
Popliteus
· Origin by a rounded tendon
· From lateral surface of lateral condyle of tibia
· From lateral semilunar cartilage
· Arises within the capsule of knee joint
· Tendon separates the lateral meniscus from lateral ligament of knee joint
· Insertion pierces the capsule of knee joint to get inserted on the posterior surface of tibia above soleal line
· Nerve supply tibial nerve
· Action
· Medial rotation of tibia on femur
· If foot is fixed lateral rotation of femur on tibia
· Un locking of knee joint
CONTENTS OF POPLITEAL FOSSA
n popliteal artery and its branches
n Popliteal vein and its tributaries
n Termination of the small saphenous vein
n Tibial & common fibular nerve
n Posterior cutaneous nerve of the thigh
n Popliteal lymph nodes & vessels.
Contents are arranged in this order from superficial to deep or from back to front:
§ Superficial fascia
§ Nerves
§ popliteal veins
§ Popliteal arteries
§ Joint capsule
Fascia of the popliteal fascia
Subcutaneous tissue overlying the fascia contains fat, the small saphenous vein & 3 cutaneous nerves
· posterior cutaneous of the thigh
· medial cutaneous sural nerve
· lateral cutaneous sural nerve
The deep fascia forms a protective sheet overlying the neurovascular structures; it is continuous with the fascia lata of the thigh & the deep fascia of the leg. This forms a loose retinaculum fro the hamstring tendons as they cross the knee. When extended the fascia stretches taught and the semimembranosus moves laterally to cover the fossa’s contents
Popliteal artery
n The popliteal artery is a continuation of the femoral artery as it traverses the adductor hiatus and moves from anterior to posterior.
n It traverses the popliteal fossa and divides into the anterior & posterior tibial arteries at the inferior border of the fossa.
n Anterior relation
· Lies on posterior surface of femur
· Knee joint
· Popliteus muscle
n Posterior relation
· Popliteal vein
· Tibial nerve
· Fascia
· Skin
Branches
1. Articular branches to knee forming an anastomosis known as genicular anastomoses
Genicular anastamoses
5 genicular branches surround the joint capsule and ligaments.
n Superior lateral genicular artery
n Superior medial genicular artery
n Middle genicular artery
n Inferior lateral genicular artery
n Inferior medial genicular artery
Importance
Peri-genicular collateral circulation maintains flow around the knee during full flexion*
2. Muscular branches
n hamstrings
n gastrocnemius end arteries
n soleus
n plantaris
Peri-Articular anastomoses
1. Descending genicular branch of the femoral artery (superior-medial)
2. Descending branch of the lateral femoral circumflex artery (superior-lateral)
3. Anterior tibial recurrent branch of the anterior tibial artery (infero-lateral)
4. Unnamed anastamoses with descending inferior gluteal branches
n Popliteal veins
Formed at the distal end of the popliteal fossa by a continuation of the posterior tibial vein. Traverses the fossa with artery in a fibrous sheath and changes to the femoral vein at the adductor hiatus. Crosses behind the artery from medial to lateral side. There are several valves located in the superior region of the fossa.
Tributaries
· The small saphenous vein passes from posterior of the lateral malleolus to the popliteal fossa where it pierces the fascial sheath to enter the popliteal vein (it may enter the posterior tibial branch).
· Veins corresponding to branches of popliteal artery
Lymph nodes:
1. Superficial – located in the subcutaneous tissue
2. Deep - located around the popliteal artery & vein
n Receive lymphatics from lateral side of foot and from knee joint
n They drain proximally to the deep inguinal nodes
n Any process in the foot can rapidly move proximally in this fashion
Nerves of the popliteal fossa:
· Sciatic nerve splits at the superior angle of the popliteal fossa to form
Tibial nerve
Common peroneal nerve:
Tibial nerve:
Formed by the anterior divisions of the anterior rami of l4-s3, this is medial, larger and more superficial branch of the sciatic nerve in the fossa. It bisects the fossa as it passes the inferior angle of the fossa.
Muscular branches:
· To the soleus, gastrocnemius, plantaris and popliteus.
Cutaneous branches
Medial sural cutaneous nerve (joined by the sural communicating branch form the common fibular) to form the sural nerve that supplies sensation to the lateral side of the leg & ankle (the level of formation of the sural nerve is quite variable). Accompanies small saphenous vein and supply sensations to lateral border of foot and lateral side of little toe
Common fibular nerve:
Formed by the posterior divisions of the anterior rami of l4-s2), lateral and smaller branch of the sciatic it follows the medial border of the biceps femoris muscle & tendon. It passes superficial to the lateral head of the gastrocnemius and passes over the posterior aspect of the head of the fibula then wraps around the fibular neck and descends antero-medially forming terminal branches:
• Superior fibular nerve – fibularis longus, fibularis brevis, skin distal anterior leg & dorsum of the foot.
• Deep fibular nerve – anterior muscles of the leg, and dorsum of the foot.
Posterior cutaneous nerve of the thigh supplies the skin over the popliteal fossa.
Branches of common peroneal in popliteal fossa
Muscular
· Short head of bicep
Cutaneous
· Sural communicating nerve
· Lateral cutaneous nerve of calf
· Skin of lateral side on the back of neck
CLINICAL CORRELATE
n Any expansible process in this area tends to cause great discomfort due to the tight fascial restrictions, early involvement of neurovascular structures and the involvement in locomotion.
n Abscesses tend to extend superiorly or inferiorly due to resistant fascial roof on the fossa.
n Aneurysmal dilatations at the bifurcation of the popliteal artery are not uncommon and often produce symptoms related the nerves traversing the fossa. .
n The close approximation of the popliteal artery to the bony structures and joint capsule puts this artery at risk with knee dislocations and distal femur or proximal tib/fib fractures.
Baker's cysts
The synovial sack of the knee joint can, under certain inflammatory circumstances, produce a posterior bulge into the popliteal fossa, behind the knee. When this bulge becomes large enough, it becomes palpable. Most baker's cysts maintain this direct communication with the synovial cavity of the knee, but sometimes a separate cyst pinches off. Baker’s cysts cause significant discomfort and impairs function, rupture is associated with acute pain which resolves and calf swelling.
Popliteal aneurysm
n Etiology related to chronic flexion/extension cycles
n presentation
pulsatile mass in the popliteal fossa
n Risks
Distal embolization
Acute thrombosis
Rupture
n Associated aneurysms – other leg, femoral, aortic.
n Treatment
n Bypass
n Stent