Lower Limb 2 - MEDIUM

Popliteal Fossa

• The popliteal fossa refers to a diamond-shaped region posterior to the knee joint.
• It is primarily a fat-filled compartment.

Popliteal Fossa Boundaries

• Biceps femoris forms the supero-lateral border.
• Semimembranosus and semitendinosus create the supero-medial border.
• The lateral and medial heads of the gastrocnemius muscle provide the infero-lateral and infero-medial borders, respectively.
• Skin and popliteal fascia make up the posterior roof.

Popliteal Fossa Contents

• Popliteal artery and its branches represent the continuation of the femoral artery.
• Popliteal vein has concomitant veins associating the anterior and posterior tibial arteries merging to form the popliteal vein.
• The tibial and common peroneal nerves are contained within.
• Termination of the lesser saphenous vein drains into the popliteal vein here.
• Posterior femoral cutaneous nerve of the thigh is present.
• Popliteal lymph nodes and vessels are located here.

Fascia and Compartments of the Leg

• The deep fascia of the leg is known as the crural fascia.
• The crural fascia provides two septa, namely the 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.
• These compartments are the anterior, lateral, and posterior compartments.
• Around the ankle joint, the crural fascia forms thickenings: superior and inferior extensor retinacula, superior and inferior peroneal (fibular) retinacula, and flexor retinaculum.
• The tendons of the leg muscles pass under these thickenings.

Anterolateral Leg

• The anterolateral leg involves the anterior and lateral compartments.
• There are four muscles within the anterior compartment of the leg.
• These include the tibialis anterior, extensor digitorum longus, extensor hallucis longus, and peroneus (fibularis) tertius muscles.
• The tibialis anterior muscle originates from the superior half of the shaft of the tibia and interosseous membrane and inserts on the medial cuneiform and base of the first metatarsal.
• It's innervated by a deep peroneal nerve, and dorsiflexes and inverts the foot.
• The extensor digitorum longus muscle originates from the shaft of the fibula and interosseous membrane.
• It inserts on the middle and distal phalanges of the lateral four toes.
• A deep peroneal nerve innervates it, and it extends the lateral four toes and dorsiflexes the foot.
• Shaft of fibula and interosseous membrane are the origin.
• Extensor hallucis longus muscle inserts on the dorsal aspect of the base of the distal phalanx of the big toe.
• That muscle is innervated by the deep peroneal nerve, and extends the big toe, and dorsiflexes and inverts the foot.
• Peroneus (fibularis) tertius muscle originates from the lower part of the shaft of the fibula and interosseous membrane.
• It inserts on the dorsum of the base of the fifth metatarsal.
• It is innervated by the deep peroneal nerve, and dorsiflexes and assists in eversion of the foot.
• Two muscles exist within the leg's lateral compartment.
• These include the peroneus (fibularis) longus muscle and the peroneus (fibularis) brevis muscle.
• Peroneus (fibularis) longus muscle originates from the superior part of the shaft of the fibula and inserts on the plantar surfaces of the base of the first metatarsal and medial cuneiform.
• The superficial peroneal nerve innervates and everts this muscle and weakly plantar flexes the foot.
• Peroneus (fibularis) brevis muscle originates from the lower 2/3 of the shaft of the fibula and inserts on the lateral side of the base of the fifth metatarsal.
• The superficial peroneal nerve innervates this muscle and it everts and weakly plantar flexes the foot.

Posterior Leg

• Posterior leg involves the posterior compartment
• The posterior compartment of the leg can be divided into superficial and deep compartments via the transverse intermuscular septum.
• Three muscles are in the superficial posterior compartment which include the gastrocnemius, soleus, and plantaris muscles.
• Gastrocnemius arises from the medial head at the medial condyle of the femur, and the lateral head at the lateral condyle of the femur.
• All attached to the posterior surface of calcaneus via calcaneal tendon.
• Supplied from the tibial nerve, the gastrocnemius plantar flexes the foot when the leg is extended, raises the feet when walking, and flexes leg.
• The soleus muscle begins at the shafts of tibia and fibula and attaches to the posterior surface of the calcaneus via the calcaneal tendon.
• Supplied from the tibial nerve, the soleus plantar flexes the foot regardless of its position, and steadies leg on foot.
• The plantaris muscle is located at lateral supracondylar ridge of femur and attaches to the posterior surface of calcaneus via calcaneal tendon.
• Supplied via the tibial nerve, it's a weak plantar flexor of the foot.
• Four muscles are in the deep posterior compartment which includes the popliteus, flexor hallucis longus, flexor digitorum longus and the tibialis posterior muscles.
• Popliteus muscle extends from the lateral condyle of femur, lateral meniscus and attaches to the posterior surface of tibia.
• Supplied by tibial nerve, it weakly flexes the knee and unlocks it by rotating femur on fixed tibia.
• Flexor hallucis longus muscle originates from the shaft of fibula and interosseous membrane, and inserts on the plantar surface of base of distal phalanx of big toe.
• Supplied by tibial nerve,it flexes great toe, and weakly plantar flexes foot.
• Flexor digitorum longus muscle originating from shaft of tibia and by a broad tendon to fibula, and inserts at the bases of distal phalanges of lateral four toes.
• Supplied by the tibial nerve, this muscle flexes lateral four toes and plantar flexes the foot.
• The tibialis posterior muscle origin is at the shafts of tibia and fibula, and interosseous membrane and inserts at the tuberosity of navicular bone, cuneiform bone, cuboid bone, and bases of 2nd, 3rd and 4th metatarsal.
• This plantar flexes and inverts the foot, receiving its innervation via tibial nerve.

Muscles of the Foot

• There is very dense layer of deep fascia runs down middle of the sole, which is plantar aponeurosis.
• The Plantar aponeurosis helps to maintain the longitudinal arch of the foot.
• Two muscles are on the dorsum of the foot and innervated by the deep peroneal nerve.
• The two muscles are extensor digitorum brevis and extensor hallucis brevis.
• The muscles of the plantar aspect of the foot function as a group and their primary function is to resist flattening and maintain the arch of the foot.
• All of the plantar muscles are innervated either by the medial plantar nerve or the lateral plantar nerve, with both being branches of tibial nerve.
• Muscles on the plantar aspect of the foot are arranged in four layers.
• First layer contains abductor hallucis, flexor digitorum brevis and abductor digiti minimi.
• Second layer consists of the quadratus plantae and lumbricals.
• Third layer is comprises by flexor hallucis brevis, adductor hallucis, and flexor digiti minimi brevis.
• Fourth layer entails dorsal interossei, plantar interossei.

Clinical Notes related to issues with the femoral nerve

• Injury to the femoral nerve leads to considerable weakness of leg extension because there's paralysis of quadriceps femoris muscle.
• Sensory loss on the anterior part of the thigh (damage to anterior cutaneous branches) coupled with the antero-medial part of the leg (damage to the saphenous nerve, a sensory branch of the femoral nerve) occurs.

Clinical Notes related to issues with the sciatic nerve

• The sciatic nerve may be compressed by the priformis muscle due to its spasm.
• Complete section of sciatic nerve is uncommon due to its deep location.
• When this occurs the leg is nearly useless.
• Extension of hip and flexion of the leg is impaired due to paralysis of hamstring muscles.
• All foot movements are lost.
• Sensory loss will involve the leg and foot, except antero-medial part of the leg, as this part innervated by saphenous nerve.

Clinical Notes related to issues with the tibial nerve

• Injury to the tibial nerve is uncommon due to it 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 paralysed.
• There will be an inability to plantar flex the foot and flex the toes.
• Sensory loss is observed on the sole of the foot.

Clinical Notes related to issues with the common peroneal nerve

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

Arteries of the Lower Limb

• Femoral artery represents the principal artery of the lower limb.
• It is actually the continuation of the external iliac artery.
• The external iliac artery becomes the femoral artery as it passes posterior to the inguinal ligament.
• The femoral artery first enters the femoral triangle.
• Leaving the triangle it passes through the adductor canal and then adductor hiatus and reaches to the popliteal fossa, where it becomes the popliteal artery.
• Branches of the femoral artery including the superficial epigastric artery, superficial circumflex iliac artery, external pudendal arteries descending genicular artery and deep artery of the thigh with its lateral and medical circumflex femoral arteries.
• Popliteal artery supplies a number of branches around knee joint.
• They participate the formation of genicular anastomoses.
• Popliteal artery terminates by giving its two terminal branches at the inferior border of the popliteus muscle.
• They are the anterior and posterior tibial arteries.
• The anterior tibial artery descends in the anterior compartment.
• It continues as the dorsal artery of the foot (dorsalis pedis artery) as it passes between the malleoli.
• It gives off the arcuate artery which gives rise to 2nd, 3rd and 4th metatarsal arteries.
• There is the Dorsal artery of the foot which terminates by giving its two terminal branches and the first dorsal metatarsal artery.
• The Deep plantar artery unites with the lateral plantar artery to form the deep plantar arch.
• Posterior tibial artery descends in the posterior compartment

Veins of the Lower Limb

• Veins of the lower limb can be classified as superficial and deep veins.
• Deep veins generally follow the arteries, with the are thus referred to as the comitant veins or provided with the same name as the artery it follows.
• Deep veins finally drain into the femoral vein.
• The femoral vein becomes the external iliac vein as it passes posterior to the inguinal ligament.

Clinical Notes relating to veins

• Cannulation of the femoral vein is used for recording the pressures and take blood samples from the right heart and/or pulmonary artery.
• A long slender catheter is inserted and advanced through the internal iliac, common iliac and inferior vena cava respectively and to the right atrium.

Veins of the Lower Limb

• Two major superficial veins exist in the lower limb.
• The great saphenous vein is located on the medial side.
• Small saphenous vein is positioned on the lateral side.
• These veins collect all the venous blood from the superficial structures.

Great Saphenous Vein

• This is the longest vein of the body.
• Ascends to the level of femoral triangle; then passes through the saphenous opening to drain into the femoral vein.

Small Saphenous Vein

• Terminates by draining into the popliteal vein.
• Drains at the level of popliteal fossa.