Lower Limb Anatomy

Thigh and Leg Compartments

• Thigh muscles are organized into three compartments including anterior (extensor), medial (adductor), and posterior (flexor).
• Compartments are separated by intermuscular septa from the inner surface of the fascia lata to the linea aspera of the femur.
• Compartments are named by location or action at the knee joint.
• Generally muscles of the anterior group are innervated by the femoral nerve.
• The medial group is innervated by the obturator nerve.
• The posterior group is innervated by the tibial portion of the sciatic nerve.
• Compartment sizes vary and the anterior compartment is the largest with the inclusion of the femur.
• The anterior compartment contains the anterior thigh muscles, flexors of the hip, and extensors of the knee.
• Anterior thigh muscles include the pectineus, iliopsoas, sartorius, and quadriceps femoris.
• Major muscles of the anterior compartment tend to atrophy (diminish) rapidly with disease.
• Physical therapy is necessary to restore strength, tone, and symmetry after immobilization of the thigh or leg.

Anterior Thigh Muscles: Flexors of Hip Joint

• Pectineus:
  • Proximal Attachment: Superior ramus of pubis
  • Distal Attachment: Pectineal line of femur, just inferior to lesser trochanter
  • Innervation: Femoral nerve (L2, L3) and may receive a branch from the obturator nerve
  • Main Action: Adducts and flexes thigh; assists with medial rotation of thigh
• Iliopsoas:
  • Proximal Attachment: Sides of T12-L5 vertebrae and discs between them, transverse processes of all lumbar vertebrae, sides of T12-L1 vertebrae and intervertebral discs
  • Distal Attachment: Lesser trochanter of femur
  • Innervation: Anterior rami of lumbar nerves (L1, L2, L3)
  • Main Action: Acts conjointly flexing thigh at hip joint and in stabilizing the joint
• Iliacus:
• Proximal Attachment: Iliac crest, iliac fossa, ala of sacrum, and anterior sacro-iliac ligaments
• Distal Attachment: Tendon of psoas major, lesser trochanter, and femur distal to it
• Innervation: Femoral nerve (L2, L3)
• Main Action: Acts conjointly flexing thigh at hip joint and in stabilizing the joint
• Sartorius:
• Proximal Attachment: Anterior superior iliac spine and superior part of notch inferior to it
• Distal Attachment: Superior part of medial surface of tibia
• Innervation: Femoral nerve (L2, L3)
• Main Action: Flexes, abducts, and laterally rotates thigh at hip joint; flexes leg at knee joint, and medially rotates leg when knee is flexed.
• The psoas major is also a postural muscle that helps control the deviation of the trunk and is active during standing.
• Sartorius, acting with three additional actions produce the once common cross-legged sitting position used by tailors, hence the name

Anterior Thigh Muscles: Extensors of Knee

• Quadriceps Femoris: Consist of four individual muscles; three vastus muscles and the rectus femoris.
  • They form the main bulk of the thigh, and collectively are one of the most powerful muscles in the body
• Rectus Femoris:
  • Proximal Attachment: Anterior inferior iliac spine and ilium superior to acetabulum
  • Distal Attachment: Via common tendinous (quadriceps tendon) & independent attachments to base of patella
  • Innervation: Femoral nerve (L2, L3, L4)
  • Main Action: Extends leg at knee joint and steadies hip joint to help the iliopsoas flex thigh
• Vastus Lateralis:
  • Proximal Attachment: Greater trochanter and lateral lip of linea aspera of femur.
  • Distal Attachment: Via common tendinous (quadriceps tendon) & indirectly via patellar ligament to tibial tuberosity
  • Innervation: Femoral nerve (L2, L3, L4)
  • Main Action: Extends leg at knee joint
• Vastus Medialis:
  • Proximal Attachment: Intertrochanteric line and medial lip of linea aspera of femur.
  • Distal Attachment: Via common tendinous (quadriceps tendon) & and medial and lateral vasti also attach to the patella and tibia via aponeuroses
  • Innervation: Femoral nerve (L2, L3, L4)
  • Main Action: Extends leg at knee joint
• Vastus Intermedius:
  • Proximal Attachment: Anterior and lateral surfaces of shaft of femur
  • Distal Attachment: Via common tendinous (quadriceps tendon) & and medial and lateral vasti also attach to the patella and tibia via aponeuroses
  • Innervation: Femoral nerve (L2, L3, L4)
  • Main Action: Extends leg at knee joint
• The four quadriceps femoris muscles unite proximal to the knee and attach to the patella via the quadriceps tendon.
• The patella is attached to the tibia by the patellar ligament and quadriceps femoris is main the extensor of the knee.
• During level walking, the quadriceps become active during the termination of the swing phase, preparing the knee to accept weight.
• Quadriceps are primarily responsible for absorbing the jarring shock of heel strike and it continues as the weight is assumed during the early stance phase.
• Quadriceps also function as a fixator during bent-knee sports, such as skiing and tennis, and contracts eccentrically during downhill walking and descending stairs.
• The patella is the largest sesamoid bone and withstands the compression on the quadriceps tendon during kneeling and friction when the knee is flexed and extended during running.
• The patellar ligament, attached to the tibial tuberosity, is the continuation of the quadriceps tendon in which the patella is embedded.

Medial Thigh Muscles & Adductors of Thigh

• Muscles of the medial thigh comprise the adductor group consisting of the adductor longus, adductor brevis, adductor magnus, gracilis, and obturator externus.
• These muscles attach proximally to the antero-inferior external surface of the bony pelvis, including the pubic bone, ischiopubic ramus, and ischial tuberosity, and adjacent obturator membrane.
• Muscles distally attach to the linea aspera of the femur.
• All adductor muscles are supplied by the obturator nerve (L2-L4), except for the "hamstring part" of the adductor magnus, which is supplied by the tibial part of the sciatic nerve (L4).
• Actions of adductors include adducting
• Adductor Longus:
  • Proximal Attachment: Inferior to pubic crest
  • Distal Attachment: Of linea aspera of femur
  • Innervation: Obturator nerve, branch of, anterior division (L2, L3, L4)
  • Main Action: Adducts thigh; to some extent flexes it
• Adductor Brevis:
  • Proximal Attachment: Body and inferior ramus of pubis
  • Distal Attachment: Pectineal line and proximal part of linea aspera of femur
  • Innervation: Obturator nerve, branch of, anterior division (L2, L3, L4)
  • Main Action: Adducts thigh; to some extent flexes it
• Adductor Magnus:
• Proximal Attachment: Adductor part inferior ramus of pubis and ramus of ischium, Hamstrings part ischial tuberosity
• Distal Attachment: Adductor part, gluteal tuberosity and linea aspera, medial supracondylar line & Hamstring part, adductor tubercle of femur
• Innervation: Adductor part, obturator nerve (L2, L3, L4), branches of posterior division & Hamstring part, tibial part of sciatic nerve (L4)
• Main Action: Adducts thigh; Adductor part flexes thigh ,and Hamstrings part extends thigh
• Gracilis:
  • Proximal Attachment: Body and inferior ramus of pubis
  • Distal Attachment: Superior part of medial surface of tibia
  • Innervation: Obturator nerve (L2, L3)
  • Main Action: Adducts thigh, also flexes leg and helps rotate leg medially
• Obturator Externus:
• Proximal Attachment: Margins of obturator foramen and obturator membrane
• Distal Attachment: Trochanteric fossa of femur
• Innervation: Obturator nerve (L3, L4)
• Main Action: Laterally rotates thigh and steadies head of femur in acetabulum
• Adductor magnus is the largest, most posterior, and most powerful muscle in the adductor group.
  • It is a composite, triangular muscle with a thick, medial margin that has an adductor part and a hamstring part, differing in their attachments, nerve supply, and main actions.
• Gracilis is a long, strap-like muscle and is both the most medial muscle of the thigh and the weakest member of the adductor group.
• It is the only one of the group to cross both the knee and hip joint.
• Gracilis is innervated by three different nerves.
• Gracilis joins the sartorius and semitendinosus muscles with a common tendinous insertion, the pes anserinus, into the superior part of the medial surface of the tibia.
• The adductor hiatus is an opening between the aponeurotic distal attachment of the adductor part of the adductor magnus and the tendinous distal attachment of the hamstring part.
  • It transmits the femoral artery and vein from the adductor canal in the thigh to the popliteal fossa posterior to the knee.
  • The opening is located just lateral and superior to the adductor tubercle of the femur.

Arteries of the Anterior and Medial Thigh

• Femoral:
  • Origin: Continuation of external iliac artery distal to inguinal ligament
• Course: Descends through femoral triangle bisecting it and courses through adductor canal continuing as the popliteal artery after traversing adductor hiatus
• Distribution: Branches supply anterior and anteromedial aspects of the thigh
• Profunda Femoris (deep artery of thigh):
  • Origin: Femoral artery 1-5 cm inferior to inguinal ligament
  • Course: Passes deeply between pectineus and adductor longus, descending posterior to the medial side of the adductor longus on the medial side of the femur
  • Distribution: Three to four perforating arteries pass through adductor magnus that winds around femur to supply the muscles in medial, posterior, and lateral part
• Medial Circumflex Femoral:
  • Origin: Profunda femoris artery which may arise from the femoral artery
  • Course: Passes medially and posteriorly between pectineus and iliopsoas, enters gluteal region giving rise to posterior retinacular arteries terminating into transverse and ascending branches ` - Distribution: Supplies blood to head and neck of femur, the transverse branch takes part in cruciate anastomosis, while the ascending branch joins inferior gluteal artery
• Lateral Circumflex Femoral:
  • Origin: Femoral artery
  • Course: Passes laterally deep to sartorius and rectus femoris and divides into ascending, transverse, and descending arteries
  • Distribution: Ascending branch supplies anterior part of gluteal region, transverse branch winds around femur, and descending branch joins genicular peri-articular anastomosis
• Obturator:
• Origin: Internal iliac artery or the inferior epigastric artery
• Course: Passes through obturator foramen entering medial compartment of the thigh and divides into anterior and posterior branches on respective sides of adductor brevis
• Distribution: Anterior branch supplies obturator externus, pectineus, adductors of thigh, and gracilis and the posterior branch supplies muscles attached to ischial tuberosity

Clinical Anatomy - Thigh

• Psoas Abscess:
  • A retroperitoneal pyogenic infection (pus-forming) in the abdomen or greater pelvis, characteristically with TB of the vertebral column or regional enteritis such Crohn disease, may result in the formation of a psoas abscess.
  • When the abscess passes between the psoas and its fascia to the inguinal and proximal thigh regions, severe pain may be referred to the hip, thigh, or knee joint.
  • A psoas abscess should be considered when edema occurs in the proximal part of the thigh.
  • Such an abscess may be palpated, observed, or mistaken for an indirect inguinal hernia, a femoral hernia, an enlargement of the inguinal lymph nodes, or a saphenous varix.
  • An obscured psoas shadow may be an indication of abdominal pathology.
• Paralysis of Quadriceps:
  • A person with paralyzed quadriceps muscles are unable to extend the leg against resistance and need to press on the distal end of the thigh during walking to prevent inadvertent flexion of the knee joint.
  • Weakness of the vastus medialis or vastus lateralis, resulting from arthritis or trauma to the knee joint, leads to abnormal patellar movement and loss of joint stability.
• Chondromalacia Patellae (runner's knee):
  • Common knee injury for marathon and running sport athletes.
  • Soreness and aching around the patella results from quadriceps imbalance and may result from a blow to the patella or extreme flexion of the knee (e.g., during squatting when power lifting).
• Patellar Fractures:
  • A direct blow to the patella may fracture it into two or more fragments.
  • Transverse fractures may result from a blow to the knee or sudden quadriceps contraction
  • Proximal fragment is pulled superiorly with the quadriceps tendon, and the distal fragment remains with the patellar ligament.
• Patellar Tendon Reflex:
  • Tapping the patellar ligament with a reflex hammer normally elicits the patellar tendon reflex (“knee jerk”).
  • Tests the integrity of the femoral nerve and the spinal cord segments L2-L4 reflex.
  • Diminution or absence may result from any lesion that interrupts the innervation of the quadriceps.

Gross Anatomy of the Leg

• The leg region (L. regio cruris) lies between the knee and the narrow, distal part of the leg including the tibia (shin bone) and fibula (calf bone).
• The ankle (L. tarsus) or talocrural region includes the medial and lateral prominences (malleoli) that flank the ankle (talocrural) joint. In non-technical use, the leg is referred to as the shank.

Bones of the Leg

• The tibia and fibula are bones of the leg; the tibia articulates with the condyles of the femur superiorly and the talus inferiorly transmitting the body's weight.
• The fibula mainly functions as an attachment for muscles for stability of the ankle joint. The shafts of the tibia and fibula are connected by a dense interosseous membrane.

The Tibia & Proximal End & Distal End

• The tibia is the main bone of the lower leg more commonly known as the shin, expanding and articulating at the knee and ankle joints respectively to support weight-bearing.
• The proximal tibia is widened by the medial and lateral condyles which form a flat surface, known as the tibial plateau to articulate with the femoral condyles forming the key articulation of the knee joint.
• The intercondylar eminence region is the main site of attachment for the ligaments and the menisci of the knee joint that articulates with the intercondylar fossa of the femur.
• The shaft of the tibia is prism-shaped, with three borders and three surfaces which are anterior, posterior and lateral.
• The palpable anterior border is marked by the tibial tuberosity and is the attachment site for the patella ligament.
• The posterior surface is marked by soleal line which blends with the medial border of the tibia and has a nutrient artery proximal to the soleal line.
• Lateral border is also known as the interosseous border to attach to the interosseous membrane that binds to the fibula.
• The distal end is widened for the medial malleolus to articulate with the tarsal bones and form part of the ankle joint.
• On the there is a fibular notch to bind the fibula forming the distal tibiofibular joint.

The Fibula

• Located within the lateral aspect of the leg, it main performs as an attachment point for muscles and is a non-weight-bearer.
• The fibula has three main articulations:
  • Proximal tibiofibular joint – articulates with the lateral condyle of the tibia.
  • Distal tibiofibular joint – articulates with the fibular notch of the tibia.
  • Ankle joint – articulates with the talus bone of the foot.
• At the proximal end, the fibula has an enlarged head with a surface of articulation with the lateral condyle of the tibia. On the posterior and lateral Surface of fibula neck, Is the common fibular nerve.
• The fibular shaft has three surfaces: anterior, lateral and posterior.
  • All three split into three comparments.
• The lateral surface continues inferiority as the lateral malleolus which can be palpated the ankle.

Clinical Anatomy of the Tibia & Fibula

• Tibia: Can use intraosseous access as vascular access at the anteromedial surface(2-3cm below tibial tuberosity) and proximal section (medial malleolus). IO access complications include osteomyelitis, iatrogenic fracture, and compartment syndrome.
• Fractures of the Tibia are relatively common with high energy traumas in younger populations and low energy traumas occuring in elderly populatiions. Medial malleolus fractures result from ankle twisting which may product unstable factures that requite management.
• Fibula: The lateral malleolus is prone to fracture and can occur in a spiral or transverse formation depending on the degree of ankle rotation and pressure.

Compartments of the Leg

• The anterior compartment of the leg (dorsiflexor/extensor compartment) is located anterior to the interosseous membrane between the lateral surface of the shaft of the tibia and the medial surface of the shaft of the fibula; bounded anteriorly by the deep fascia of the leg and skin.
• Two band-like thickenings of the fascia form retinacula to bind the tendons of the anterior compartment muscles before and after crossing the ankle joint as preventative measures to bowstringing during dorsiflexion of the joint.

Anterior Compartment of Leg

• Four muscles pass and insert anterior to the transverse axis of the talocrural joint and are controlled by the tibial anterior, extensor digitorum longus, extensor hallucis longus, and fibularis tertius.
• The extensor digitorum longus and extensor hallucis longus also extend the toes.
• The anterior compartment’s muscles are innervated by the deep fibular nerve (L4-S1), blood supplied via the anterior tibial artery.
• Tibialis Anterior lies alongside the lateral surface of the tibia, is the strongest dorsiflexor of the foot, originates from the lateral surface of the Tibia, attaches to the base of metatarsal l, performs dorsiflexion+inversion and is innervated by the deep fibular nerve.
• Extensor digitorum longus lies lateral and deep to tibialis anterior, tendons can be palpated on the dorsal surface of the foot, fibres converge into a tendon travels to the tendon splits into four inserting onto a toe, to extend the lateral four toes and dorsiflex the dorsiflex and is innervated by the deep fibular nerve..
• Extensor Hallucis Longus is deep to the EDL/Tibialis anterior, is on the medial surface and attaches is dorsal phalanx of the great toe. it Performs dorsal fexion plus extension of the great toe and is also innervated by the deep fibular nerve.
• The Fibularis tertius arises from the most inferior part of the eDL/medial surface, and is the tendon attached to metatarsal V to evert+ dorsiflex. The nerve supply is the deep fibular Nerve.
• The deep fibular (peroneal) nerve services the anterior, fibularis longus and brevis muscles

Lateral Compartment of the Leg

• Referred to as the evertor compartment, is the smallest section is is bounded behind the fibula anterior lateral septa and deep fascia ends at the superior fibular retinaculum with its passage ending in the the lateral malleolus .
• The fibularis longus (FL) is the longer, mor superficial of the two fibularis muscles attaching from the head of the fibula to the sole of the foot on the medial cuneiform bone and perform leg steadies and feet eversion
• The fibularis brevis (FB)underlices the muscle , traverses it from behind, with the Tendon attacing at the base of the 5th metatarsal , which is an offshoot from the fibularis longus

Leg

• Located in the largest and most posterior region, it is the superficial group of calf muscles with the calcaneal tendon being its thickest point, with there being smaller muslces which plantar +inverte + flex the toes. These smaller muscles are at the lower end of lateral condyle attached to all that follows,

Clinical Relevance of the Muscles, The Ankle Joint, Veins of the Lower Limb

• Footdrop: -Clinical sign indicating paralysis of the muscles in the anterior compartment of the leg.
  • Typically is occurs as a form of common fibular nerve damage, with limited capacity to plantar flex.

The Ankle Joint

• Synovial and in nature with leg bones forming , The tibia + fibula from part of that while the rest is linked to a bone in the foot The main point occurs where, at point of dorsiflexion the anterior locks into place while plantar is most unstable, It has several distinct layers.
• Medial Ligs form protection over overeversion while later are against hyperinversion

Movements and Muscles Involved

• Ankle is hinge joint .
• The Posterior compartment is known for Plantarflexion and its gastrocnemius, soleus, plantaris , while Dorsiflexion is a function of the anterior leg compartment, and is powered by the extensor hallucis longus ect. Nerve supply involves tobial superficial fibula and depp fibular and arterial supply derivers as mallar from tibial and fibula aritereis.

Clinical Relevance

• Ankle Sprain, in both partial and complete forms, is du damage in joint, The main area affected can be damaged is hyperinversion and there is damage over the lateral portion.

Pott's Fracture-Dislocation

• Bimalleolar or trimalleolar fracture caused by forceful eversion

The Ankle 'Ring

• Parts linked with the artualted surface of the tibia in terms of ring integrity
• This integrity breaks when an instancing force acts on and it’s difficult to break as the rest is with ligament

Veins

• Deep are under the vein
• Superficial ones are found in subcutaneous
• The main one of the foot is at the arch which drains into the superior and enters the tibia
• Lateral veins are found but that connects to the posterior Then they combine to form the poplitcal Vein which enters the thigh.

Issues

• Deep vein Thrombosis

Genu Valgum and Varum

• Region is drained via supieeior and inferior veins, but more from the inferior portion.
• In the legs, blood comes from the upper most point and there are Valves preventin going to the lungs in an mechanical shock. But can be prevented from the great sapehenous vein by the doras vein entering the medial maellesus or the inferior in the patella.

Small Saphenous Vein is just behind the great and goes into the popeteal fosa. Complications can arise at the limbs by drawing in the skin which prevents backfllow/incompotent causing them to swell. This can lead to Varicose veins where blood needs to go into the artery by cutting and moving or useing thermablatoin to heat, and close the path.

Questions cover the anatomy and function of the thigh and leg. It includes muscles, nerves, and ligaments. Learn about the different thigh compartments, muscle innervations, and the function of the fibula.