Proximal neurovasculature, Knee and Leg Flashcards
Sacral plexus: Label picture
Where is it found?
What are the main exit points?
What are the branches? What do they supply?
What else can be found in this area?
- Sacral plexus = network of nerve fibres that supplies skin and muscles of pelvis and lower limb
- Located on posterolateral pelvic wall anterior to piriformis muscle
- Formed by anterior rami/ ventral rami from L4- S4.
- Sacral plexus begins as anterior fibres of S1-S4 and are joined by L4/L5 which combine to form lumbosacral trunk. The L4/L5 spinal nerves descend to meet sacral roots as they emerge from spinal cord.
- Two main exit points –>
- greater sciatic foramen, nerves going to gluteal region
- Remain in pelvis –> innervate pelvic muscles/ organs/ perineum
Branches:
- First see the lumbosacral trunk contributing L4/L5 to sacral plexus
- Then superior gluteal nerve coming off, leaving via greater sciatic foramen going to innervate the gluteus medius/ minimus muscles/ tensor fascia latae. (Loss leads to dropping of pelvis on weak side).
- becomes the sciatic nerve (L4-S3) which innervates the posterior thigh, leg and foot. Loss leads to weakness of lower limb muscles
- Pudendal portion (S2-S4) --> innervates skeletal muscles of perineum, external urethral sphincter and exeternal anal sphincter, levator ani. Sensory to external genitalia.
- Can also see sympathetic chain and nerve to levator ani.
What is a good mnemonic for the sacral plexus?
Some irish sailor pesters polly
Superior gluteal nerve (L4-S1)
Inferior gluteal nerve (L5, S1, S2) –> innervates gluteus maximus
Sciatic nerve (L4- S3) –> tibial portion to muscles of posterior thigh, hamstring component adductor magnus, posterior leg and foot. Common fibular portion –> short head biceps femoris, all muscles anterior and lateral compartments of leg
Posterior femoral cutaneous (S1-S3) –> innervates skin on posterior thigh/ leg/ perineum
Pudendal (S2-S4) –> sphincters, skeletal muscle of pelvis, genitalia
Describe the lumbar plexus:
branches
- Lumbar plexus formed from anterior/ ventral rami of spinal nerves L1-L4.
- Lumbar plexus has 6 major peripheral nerves which descend down posterior abdominal wall to reach the lower limb:
- Iliohypogastric nerve (L1) –> innervates internal oblique and transversus abdominis
- Ilioinguinal (L1) –> innervates internal oblqique and transversus abdominis
- Lateral cutaneous nerve of thigh (L2, L3) (lateral femoral cutaneous nerve LFCN) –> Innervates the anterior and lateral thigh down to knee
- Femoral nerve (L2-L4) –> innervates iliacus, pectineus, sartorius and quadriceps femoris, sensory to anterior thigh and medial leg
- Genitofemoral nerve (L1, L2) –> Genital branch to cremasteric muscle, sensory to scrotum/ mons pubis and labia majora, anterior thigh
- Obturator nerve (L2,3,4) –> innervates obturator externus, pectineus, adductor longus, brevis, magnus and gracilis.
- Lumbosacral trunk (L4, L5) --> runs to join sacral plexus.
Describe the course of the lateral cutaneous nerve into the thigh
- Lateral cutaneous nerve enters thigh close to the ASIS, emerges superficial to sartorius
- It can become compressed leading to loss of sensation on atnerior lateral thigh, burning sensation
- Compression of Lateral cuteanous nerve = meralgia paraesthetica or calvin klein syndrome
- Compression can simply be due to trousers/ belt
Describe/ draw the arterial tree of the lower limb
Describe the femoral triangle and its contents
What is the clinical relevance?
How do the vessels pass into the popliteal fossa?
- Femoral triangle borders:
- Superiorly by inguinal ligament running between ASIS and pubic tubercle
- Laterally by sartorius
- Medially by adductor longus
- Contents from medial to lateral: (lymph VAN).
- Most medial = lymphatics, cloquets node
- femoral vein
- femoral artery
- femoral nerve
- Clinically:
- Femoral pulse felt at midinguinal point (halfway between ASIS and pubic tubercle)
- Access to femoral artery -> located superficially, can be accessed for procedures such as coronary angiography
- Pass through the subsartorial/ adductor canal, before passing through adductor hiatus to reach popliteal fossa.
Label the image
Describe the blood supply from the common iliac to the lower limb
- Common iliac –> internal and external iliac arteries
- Internal iliac –> pelvis and gluteal region
- external iliac –> continues as the femoral artery
- Femoral artery gives off deep branch –> profunda femoris –> gives off 3 more branches:
- medial and lateral circumflex branches –> Medial circumflex to femur head (loss leads to avascular necrosis) , lateral to lateral femur and muscles
- Perforating branches –> supply muscles of medial and posterior thigh
- Femoral artery travels through subsartorial canal and adductor hiatus into the popliteal fossa
- Becomes popliteal artery –> exits between gastrocnemius and popliteus, gives off anterior tibial artery and tibioperoneal trunk
- Tibiperoneal trunk continues posteriorly dividing into posterior tibial and fibular artery.
What is the relevance of a pelvic rim fracture?
- Pelvic rim fracture can lacerate vessels supplying lower limb, epecially arteries running over sacroiliac joint (internal iliac artery).
- Must stabilise patients with pelvic rim fractures to prevent laceration of arteries and bleed out
Describe the adductor canal
When does it begin
what are its contents
where do they run to?
- Adductor canal runs deep to sartorius down the middle 1/3 of the medial thigh to the adductor hiatus (in addutor magnus)
- Femoral artery enters adductor canal after entering thigh at midingunal point (+/- 1cm medial/lateral).
- Runs into adductor canal with femoral vein and saphenous nerve
- Femoral artery and vein then pass deep and posterior at the adductor hiatus to enter the popliteal fossa
- Saphenous nerve continues to innervate the knee and skin of medial leg and foot
What has this patient suffered from?
What is the treatment?
What is the danger with this condition?
- Compartment syndrome in the anterior compartment of the thigh
- A fasciotomy has been done, incised the fascia of the iliotibial tract
- Danger of compression of the femoral artery which supplies the entirety of the thigh leg and foot, leads to hypoxia and tissue necrosis, therefore it is an emergency and pressure must be released.
Describe the lymphatic drainage of the lower limb
Superficial groups
- Superficial inguinal lymph nodes are split into a horizontal group just below the inguinal ligament
- And a vertical group that follow the proximal part of the great saphenous vein
- The superficial inguinal lymph nodes drain into the deep inguinal lymph nodes
Describe the lymph drainage of the lower limb :
Deep lymph nodes
What structures drain here?
- Horizontal and vertical superficial lymph node groups drain into the deep lymph nodes
- Deep inguinal lymph nodes are within the femoral canal medial to the femoral vein.
- Cloquet’s node sits within the femoral canal
- Lymph from lower limb, perineal region (incl. penis/ lower vagina/ lower anal canal/ anterior labia majora/ scrotal skin) all drain here.
- Lymph adenopathy in the inguinal region can be the first sign of a perineal metastatic cancer.
What is the relevance of the entry point of the great saphenous vein?
- The great saphenous vein runs superficially to meet the femoral vein.
- It travels deep in the femoral triangle and can develop a varicosity here
- It can dilate forming a saphena varix, mimicking a femoral hernia.
Label the image
To note:
- Tibial tuberosity –> attachment point for patella tendon
- Fibula head does not form the knee joint
- Fibula shaft is not needed, can be used for mandibular reconstruction
- Interosseous membrane is a syndesmosis, fibrous joint between the tibia and fibula
Label the image
How would a patient present with anterior compartment dysfunction?
- Anterior compartment allows dorsiflexion (lifting of the foot) and inversion (turning of foot inwards).
- Loss of ability to lift foot during walking leads to foot drop, compensated for by high stepping gait with toe landing or if the hip is dysfunctioning circumduction gait.
What type of joint is the knee joint?
What movements can occur at the knee?
- Knee joint = modified hinge and synovial joint
- Movements:
- flexion and extension
- medial and lateral rotation
- Translocation –> sliding of bones over each other, prevents wear and tear.
What three bones form the knee joint?
What articulations are there in the knee joint?
What are joint surfaces covered in?
- Knee joint is formed by the articulations of the femur, tibia and patella
- Knee joint consists of two articulations:
- Tibiofemoral articulation –> between the medial and lateral condyles of the femur and the tibial condyles (weight bearing joint)
- Patellofemoral –> between the anterior aspect of the femur and patella (allows quadriceps femoris to insert directly over knee increasing efficiency of the muscle).
- Both joint surfaces covered in hyaline cartilage
Label the image
What is the intercondylar eminence formed by?
The intercondylar eminence is formed by the attachment of the anterior and posterior cruciate ligaments
What are the menisci of the knee joint?
What are their functions?
- Medial and lateral menisci are C-shaped/ Crescent shaped fibrocartilage structures sat on the tibial condyles, attache to the intercondylar area of tibia
- They increase the contact area of the knee joint, deepening articular surface of tibia.
- Are weight bearing
- Act as shock absorbers by increasing SA to dissipate forces
- participate in knee locking
- Medial meniscus also attaches to the medial collateral ligament/ tibial ligament, if tibial ligament is damaged it can also damage the medial meniscus, increasing risk of degeneration
What type of bone is the patella? What does it articulate with?
What is its function?
what is it covered with?
What inserts onto the patella?
what does the patella insert onto?
- Patella = sesamoid bone that articulates posteriorly with the femoral condyles
- Function:
- Reduces ligament and tendon wear
- spreads forces passing to femoral condyles
- Increases the efficiency / moment (mechanical bending force) of the quadriceps muscles
- Quadriceps femoris tendon inserts onto tibial tuberosity via the patella, which is contained within it
- Continues at the patella ligament which inserts onto the tibial tuberosity.
What two pathologies are shown?
What two key ligaments support the knee joint?
How do they support the knee joint?
What can damage them?
- Anterior and posterior cruciate ligaments which resist anterior- posterior translocation (sliding of the femur and tibia) and rotation of the knee
- Named according to their position of origin on the tibia:
- anterior cruciate ligament from anterior tibia, travels up and posterior to insert on femur –> prevents anterior translocation of tibia on femur
- posterior cruciate ligament from posterior tibia, travels up and anterior to insert on femur –> prevents posterior translocation of the tibia on femur
- Ligaments can be damaged when placed under excess tension
How can cruciate ligament function be tested?
- Drawer test where patients knee is at 90 degrees flexion, examiner tests tibial movement both forward and backward. Excess anterior movement of tibia or lack of end point suggests ACL tear, excess posterior movement suggests PCL tear.
- Lachman test (20 degrees flexion), again stabilise knee joint, examiner moves tibia forward/ backward. Better more sensitive test for ACL damage, reduces false negatives produced by hamstring tension.
What other ligaments support the knee?
- Medial (tibial) and lateral (fibula) collateral ligaments help support the knee
- Resist valgus (distal limb away from midline) and varus forces at the knee (distal limb towards midline).
- Lateral collateral ligament keeps the tibia in abducted position, prevents over adduction. Damage to LCL can occur with excess force medially (i.e varus stress). Loss of LCL leads to tibia being pulled medially - adduction -> varus deformity.
- Medial collateral ligament keeps tibia from being over abducted. Damage occurs from excess lateral stress/ valgus stress, leads to tibia becoming abducted/ valgus deformity.
Describe the blood supply to the knee
- Blood supply to the knee is extensive and anastomotic
- Tibial/ femoral fractures do not normally result in avascular bone necrosis
Describe the bursae around the knee
Bursa = synovial fluid filled sac found at point of wear/ tear on knee joint
4 main bursae of knee joint:
- Suprapatella bursa –> extension of synovial cavity of knee located between
- quadriceps femoris and femur
- Prepatella bursa –> found between apex of patella and skin
- Infrapatella bursa –> split into deep and superficial, deep between tibia and patella ligament, superficial between patella ligament and skin
- Semimembranous bursa –> located posteriorly in knee joint between semimembranous muscle and medial head of gastrocnemius
What is inflammation of the bursa called? How can this occur?
What clinical test can check for bursitis?
- Bursitis and due to overuse of the knee joint
- Prepatellar bursitis, infrapatellar bursitis
- Suprapatellar bursa communicates with knee joint cavity
- Clinical test = patella tap, milk the suprapatella bursa inferiorly then press patella posteriorly, should tap against the femur. Tap sensation felt if there is excess fluid.
What happens during full extension of the knee?
What can reverse this movement?
- femur rotates medially on the tibia and “locks”, this puts it into its most stable and supportive position
- Passive movement under which ligaments are under tension
- Locking of the knee is reverse by the popliteus muscle –> unlocks the knee by lateral rotation
- Innervated by the tibial nerve (L5, S1)
- Popliteus muscle = deep flexor of the knee, arising from lateral femur and inserting onto medial tibia.
What muscles dorsiflex the ankle?
What muscles plantarflex the ankle?
- Ankle dorsiflexion –> tibialis anterior, Extensor hallucis longus, extensor digitorum longus (anterior compartment muscles)
- Ankle plantarflexion –> Gastrocnemius, soleus, flexor digitorum longus, flexor hallucis longus, fibularis longus, fibularis brevis (posterior and lateral compartment muscles).
What muscles invert the foot and resist excessive eversion?
What muscles evert the foot and resist excessive inversion?
Foot inversion:
Tibialis anterior and tibialis posterior
Foot eversion:
fibularis longus and fibularis brevis
Describe the anterior compartment of the lower leg:
General action
Innervation
Blood supply
Muscles
- Anterior compartment generally acts to dorsiflex the ankle and invert the foot
- Innervated by the deep fibular nerve (L4, L5, S1)
- Supplied by the anterior tibial artery
Muscles:
ibialis anterior –> located alongside lateral surface of tibia, strongest dorsiflexor. Originates at lateral tibia, inserts onto medial cuneiform and base of metatarsal 1.
Extensor digitorum longus –> lies lateral and deep to tibialis anterior, originates lateral condyle of tibia, forms a tendon travels to dorsum of foot, splits into 4 each inserting onto a toe. Extension of lateral 4 toes and dorsiflexion of foot
Extensor hallucis longus –> deep to TA and EDL. Originates medial fibular shaft, tendon crosses anterior ankle and inserts to base of distal phalanx of great toe. Extends big toe, dorsiflex foot.
Describe how the deep fibular nerve gets to the anterior compartment of the leg
Where might this course be vulnerable?
what would occur with anterior compartment dysfunction?
- Sciatic nerve enters the popliteal fossa and splits into the tibial nerve and the common fibular nerve
- Common fibular nerve splits of at medial border of biceps femoris. It runs laterally over the head of the fibula, and is subcutaneous here. –> risk of damage/ compression
- Runs into lateral compartment of the leg giving off superficial branch (innervates lateral compartment) and deep branch that will innervate anterior compartment.
- Dysfunction of anterior compartment -> foot drop, commonly caused by damage to common fibular nerve, unopposed plantarflexion.
Describe the lateral compartment of the leg:
General function
Innervation
Blood supply
Muscles
- General function –> eversion of the foot and weak plantarflexion
- Innervation –> superficial fibular nerve (L5 , S1)
- Blood supply –> Fibular artery
Muscles:
Fibularis longus –> originates lateral condyle tibia, superior/ lateral fibula, fibres converge into a tendon passes inferior to lateral malleolus, travels under the foot, inserts onto metatarsal 1 –> eversion of foot
Fibularis brevis –> deeper and shorter than fibularis longus. From fibula shaft, travels under lateral malleolus, inserts onto metatarsal V tuberosity.
FB can contract so strongly it leads to metatarsal V tuberosity avulsion fracture.
Describe the posterior compartment of the lower leg
General action
Innervation
Blood supply
Muscles
- General action: foot and digit plantarflexion, inversion
- Innervation: Tibial nerve ( S1-S2)
- Blood supply: posterior tibial artery
Muscles: Superficial
Gastrocnemius: Most superficial, two heads (medial and lateral from respective condyles on femur) that converge to form single muscle belly. Combines with soleus to insert onto calcaneal tendon which inserts onto calcaneus. Crosses the knee so flexes, and plantar flex ankle
Soleus: Deep to gastrocnemius, originates at tibia inserts onto calcaneal tendon.
Plantaris (small muscle, between heads of gastrocnemius). Flexor of knee and plantar flexion of foot at ankle
Muscles: Deep:
Popliteus –> unlocks the knee to allow flexion, rotates femur laterally on tibia.
Tibialis posterior –> originates interosseus membrane, enters foot posterior to medial malleolus, attaches to plantar surface of medial tarsal bones
Flexor digitorum longus –> from medial tibia, attaches to plantar surface of lateral 4 digits, flexes lateral 4 toes
Flexor hallucis longus –> Originates posterior fibula, attaches to plantar surface great toe, flexes great toe
Describe the popliteal fossa :
Borders
Contents
What normally fills it?
Borders:
- Superomedial border –> Semimembranosus
- Superolateral –> Biceps femoris
- Inferomedial –> medial head gastrocnemius
- Inferolateral –> lateral head gastrocnemius/ plantaris
- Floor –> formed by posterior surface of knee capsule
Contents (from medial to lateral):
- Popliteal artery (deepest structure)
- popliteal vein
- tibial nerve (branch of sciatic)(superficial)
- common fibular nerve (branch of sciatic)(superficial)
- Popliteal fossa normally filled with fat.
Label the image
What are common reasons for swellings in the popliteal fossa?
- Baker’s cyst = inflammation of semimembranosus bursa, usually arises with arthritis of knee.
- Popliteal aneurysm –> dilation of artery greater than 50% normal diameter. Can compress the tibial nerve, leading to weakened plantar flexion and parasethesia of foot and posterolateral leg.
- Rarer causes: popliteal cyst, DVT, neoplasm, neuroma
