Lower Limb 2 - EASY

Popliteal Fossa

• This is a diamond-shaped region posterior to the knee joint
• The popliteal fossa is mostly a fat-filled compartment

Boundaries

• Biceps femoris is the supero-lateral boundary
• Semimebranosus and semitendinosus are the supero-medial boundaries
• Lateral and medial heads of the gastrocnemius muscle make up the inferolateral and inferomedial boundaries
• The skin and popliteal fascia form the posterior roof of the fossa

Contents

• Includes the politeal artery and its branches, which are a continuation of the femoral artery
• The popliteal vein has comitant veins that are associating the anterior and posterior tibial arteries, and unite to form the popliteal vein
• Tibial and common peroneal nerves are present
• Termination of the lesser (small) saphenous vein is here, draining into the popliteal vein
• There is also the posterior femoral cutaneous nerve of the thigh
• Popliteal lymph nodes and lymph vessels are contents of the fossa

Fascia and Compartments of the Leg

• The deep fascia of the leg is called the crural fascia
• The crural fascia gives off two septa, anterior and posterior intermuscular septa
• The interosseous membrane extends between the tibia and fibula
• The anterior and posterior intermuscular septa, along with the interosseous membrane, divide the leg into three compartments: anterior, lateral, and posterior
• Around the ankle joint, the crural fascia forms thickenings including superior and inferior extensor retinacula, superior and inferior peroneal (fibular) retinacula, and the flexor retinaculum
• Leg muscle tendons pass under these thickenings

Anterolateral Leg

• This part involves the anterior and lateral compartments

Anterior Compartment

• There are four muscles within:
  • Tibialis anterior muscle
  • Extensor digitorum longus muscle
  • Extensor hallucis longus muscle
  • Peroneus (fibularis) tertius muscle

Tibialis Anterior Muscle

• Superior half of the shaft of tibia and interosseous membrane is a feature
• The medial cuneiform and the base of the first metatarsal are involved
• Deep peroneal nerve
• This muscle dorsiflexes and inverts the foot

Extensor Digitorum Longus Muscle

• Shaft of fibula and interosseous membrane
• Middle and distal phalanges of lateral four toes
• Deep peroneal nerve
• Extends lateral four toes and dorsiflexes the foot

Extensor Hallucis Longus Muscle

• Located on the shaft of fibula and interosseous membrane
• Dorsal aspect of base of distal phalanx of big toe
• Deep peroneal nerve
• This muscle extends the big toe, and dorsiflexes and inverts the foot

Peroneus (fibularis) Tertius Muscle

• It is a separated part of the extensor digitorum longus
• Lower part of shaft of fibula and interosseous membrane
• Dorsum of base of fifth metatarsal
• Deep peroneal nerve
• This muscle dorsiflexes and assists in eversion of the foot

Lateral Compartment

• There are two muscles:
  • Peroneus (fibularis) longus muscle
  • Peroneus (fibularis) brevis muscle

Peroneus (fibularis) Longus Muscle

• Found on the superior part of the shaft of the fibula
• Plantar surfaces of base of first metatarsal and the medial cuneiform
• Superficial peroneal nerve
• Everts and weakly plantar flexes the foot

Peroneus (fibularis) Brevis Muscle

• Located on the lower two thirds of the shaft of the fibula
• Lateral side of base of fifth metatarsal
• Superficial peroneal nerve
• This muscle everts and weakly plantar flexes the foot

Posterior Leg

• This part involves the posterior compartment
• The transverse intermuscular septum divides the posterior compartment into superficial and deep compartments

Superficial Posterior Compartment Muscles

• There are three: Gastrocnemius, Soleus, and Plantaris

Gastrocnemius Muscle

• The medial head is on the medial condyle of the femur
• The lateral head is on the lateral condyle of the femur
• Attaches to the posterior surface of calcaneus via the calcaneal tendon
• Tibial nerve
• This muscle plantar flexes the foot when leg is extended and flexes leg

Soleus Muscle

• Shafts of tibia and fibula
• Posterior surface of the calcaneus via calcaneal tendon
• Tibial nerve
• This muscle plantar flexes the foot regardless of the position, steadies the leg on the foot

Plantaris Muscle

• Lateral supracondylar ridge of femur
• Posterior surface of calcaneus via calcaneal tendon
• Tibial nerve
• This muscle is a weak plantar flexor of the foot

Deep Posterior Compartment Muscles

• Four muscles involved:
  • Popliteus muscle
  • Flexor hallucis longus muscle
  • Flexor digitorum longus muscle
  • Tibialis posterior muscle

Popliteus Muscle

• Lateral condyle of femur, lateral meniscus
• Posterior surface of tibia
• Tibial nerve
• Weakly flexes the knee and unlocks it by rotating the femur on fixed tibia

Flexor Hallucis Longus Muscle

• Found on the shaft of the fibula and interosseous membrane
• Dorsal aspect of base of distal phalanx of big toe
• Deep peroneal nerve
• This muscle extends the big toe, and dorsiflexes and inverts the foot.
• Plantar surface of base of distal phalanx of big toe
• Tibial nerve
• This muscle flexes the great toe and weakly plantar flexes the foot

Flexor Digitorum Longus Muscle

• Shaft of tibia and by a broad tendon to fibula
• Bases of distal phalanges of lateral four toes
• Tibial nerve
• This muscle flexes the lateral four toes and plantar flexes the foot

Tibialis Posterior Muscle

• Shafts of tibia and fibula, and interosseous membrane.
• Insertion is on the tuberosity of the navicular bone, cuneiform bone, cuboid bone and bases of 2nd, 3rd, and 4th metatarsal
• Tibial nerve
• This muscle plantar flexes and inverts the foot

Muscles of the Foot

• There is a dense layer of deep fascia running down the middle of the sole called the plantar aponeurosis
• The plantar aponeurosis helps to maintain the longitudinal arch of the foot
• There are two muscles on the dorsum of the foot, innervated by the deep peroneal nerve: extensor digitorum brevis and hallucis brevis
• Plantar muscle function as a whole unit, in order to resist flattening and maintain the arch of the foot
• All of the plantar muscles are innervated by either the medial or lateral plantar nerves (branches of the tibial nerve)
• Muscles on the plantar aspect of the foot are arranged in four layers:

Muscles in the First Layer

• Abductor hallucis
• Flexor digitorum brevis
• Abductor digiti minimi

Muscles in the Second Layer

• Quadratus plantae
• Lumbricals

Muscles in the Third Layer

• Flexor hallucis brevis
• Adductor hallucis
• Flexor digiti minimi brevis

Muscles in the Fourth Layer

• Dorsal interossei
• Plantar interossei

Clinical Notes: Injury to the Femoral Nerve

• It leads to a considerable weakness of the leg extension due to paralysis of quadriceps femoris muscle Patients compensate by pressing the distal end of leg during walking
• There will be sensory loss on the anterior part of the thigh and anteromedial part of the leg

Clinical Notes: Injury to the Sciatic Nerve

• The nerve may be compressed by the priformis muscle due to its spasm
• A complete sectioning is uncommon due to its deep location
• When this occurs, the leg is nearly useless:
  • Extension of the hip and flexion of the leg is impaired
  • All foot movements are lost
  • Sensory loss involves the leg and foot, except the anteromedial part of the leg

Clinical Notes: Injury to the Tibial Nerve

• Uncommon due to its deep location
• May occur in posterior dislocation of the knee joint and deep lacerations of the popliteal fossa
• Plantar flexors within the posterior compartment of the leg and muscles of the sole of the foot will be paralyzed
• Patients will be enable to plantar flex the foot and flex the toes
• Sensory loss will be observed on the sole of the foot

Clinical Notes: Injury to the Common Peroneal Nerve

• Most often injured nerve of the lower limb, due to its superficial position around the neck of the fibula
• Direct trauma or fracture of the fibular neck may damage this nerve
• Patients will be enable to dorsiflex and evert the foot
• When the foot is raised foot drop will be observed, also foot will be drawn to an inverted position
• Sensory loss will be observed on the anterolateral parts of the leg and dorsolateral parts of the foot

Arteries of the Lower Limb

• The femoral artery is the principal artery of the lower limb and is the continuation of the external iliac artery
• The external iliac becomes the femoral artery as it passes posterior to the inguinal ligament
• The femoral artery enters the femoral triangle, then passes through the adductor canal and adductor hiatus
• It reaches the popliteal fossa, where it becomes the popliteal artery

Branches of the Femoral Artery

• Superficial epigastric artery
• Superficial circumflex iliac artery
• External pudendal arteries
• Descending genicular artery

Deep Artery of the Thigh

• Lateral circumflex femoral artery
• Medial circumflex femoral artery
• The popliteal artery supplies a number of branches around the knee joint for the formation of genicular anastomoses
• The popliteal artery terminates by giving its two terminal branches at the inferior border of the popliteus muscle: anterior tibial and and posterior tibial artery
• The anterior tibial artery descends in the anterior compartment
• It continues as the dorsal artery of the foot or dorsalis pedis artery as it passes between the malleoli
• Branching into the arcuate artery which gives rise to 2nd, 3rd, and 4th metatarsal arteries
• The dorsal artery of the foot terminates by creating the first dorsal metatarsal and deep plantar artery
• The posteior tibial artery descends in the posterior compartment
• This has the peroneal (fibular) artery as a branch
• The posterior tibial artery gives off its two terminal branches as it reaches the sole of the foot by passing posterior to the medial malleolus These are the medial and lateral plantar arteries

-A clinical note states that the 5 P signs are: pain, pallor, paresthesia, paralysis and pulselessness

Veins of the Lower Limb

• There are superficial and deep veins
• Deep veins follow the arteries as comitant veins with the same name as the artery
• Deep veins drain into the femoral vein
• The femoral vein becomes the external iliac vein as it passes posterior to the inguinal ligament

Superficial Veins

• Great saphenous vein and small saphenous vein. These collect all the venous blood from the superficial structures.
• Great saphenous vein ascends to the level of the femoral triangle and passes through the saphenous opening to drain into the femoral vein
• The small saphenous vein terminates by draining into the popliteal vein, at the level of popliteal fossa