Anatomy of Thigh in a Nutshell

Anterior thigh

Dermatome:

• L1: inguinal ligament
• Going inferiorly, have bands for L2,3,4,5.
• Patella is in L4
• L5 is most of anterior leg and dominates top of the foot

Deep to skin on anterior thigh (526)

• Have superficial veins, cutaneous nerves
• Have terminal branches of lateral cutaneous nerve of the thigh (radiate along lateral aspect)
• Other nerves are branches of femoral nerve which are sensory for medial thigh
• Sensory innervation in anterior: 2 sources
  • Femoral
  • Lateral cutaneous nerve
• Great saphenous vein (AKA long saphenous vein)
  • Has beginnings on dorsal aspect of foot
  • Crosses ankle joint on medial side of leg
  • Goes into thigh and up to the region of inguinal ligament
  • Is a source for replacement vessels for coronary bypass.
  • Inferior to inguinal ligament, have saphenous opening in the fascia lata

1. 1. • Great saphenous vein passes through this saphenous opening
      • Dumps into deeper femoral vein

• Subcutaneous veins in lower limb communicate with deep veins
  • Thus, removal of a segment won’t compromise flow
  • Edema will remain shortly before other veins sprout into the region
• Other veins also pass into saphenous opening to dump into femoral
  • Superficial epigastric (with artery)
  • Anterior labial / scrotal vein→ into external pudendal (with artery)
  • Superficial dorsal vein of penis / clitoris→ into external pudendal vein
  • Saphenous vein has no companion artery
  • Superficial circumflex iliac vein

Inguinal region of proximal thigh (528)

• Lymphatic system in subcutaneous tissue associated with saphenous opening
  • Some nodes are parallel to inguinal ligament = transverse group
  • Others are more verticle
  • Collectively they are the superficial inguinal lymph nodes
    • May be enlarged due to infection in drainage field
    • Drainage field includes:
      1. All subcutaneous structures of lower limb (buttocks, thigh, leg, foot)
      2. Anterior abdominal wall below the umbilicus
      3. External genitalia (except testicles)
      4. Lower ½ of anal canal. (upper ½ goes to iliac nodes in the pelvis)

Compartments (487)

Anterior compartment: Extensors of the knee. All by femoral nerve.

• Sartorius
  • Origin: anterior superior iliac spine
  • Crosses knee joint, attaches medial aspect of tibia
  • Long strap like muscle, crosses both hip and knee
  • Flexes hip and knee, and externally (laterally) rotates the hip joint (not by itself, only facilitates)
• Tensor Fascia Lata
  • Also discussed in the posterior compartment
  • Is anterior to axis of hip joint, thus it flexes the hip joint
  • Put into posterior compartment due to nerve supply
• Iliopsosas
  • Passes deep to inguinal ligament
  • Is combo of psoas major and iliacus

1. 1. • As they descend out of iliac fossa, they unite
      • Forms common tendon to form iliopsoas

1. • Attaches lesser trochanter of femur
   • Is the only muscle that attaches the lesser trochanter
   • Function:

1. 1. • Is very powerful, is the primary hip flexor.
      • If the hip is fixed by other muscles and iliopsoas flexes, it will flex the vertebral column.

• • • Proper sit-ups remove iliopsoas out of use by Active insufficiency (it has already flexed the hip, thus can’t work well to flex trunk).

• Group: Quadroceps Femoris– 4 muscles
  • Rectus femoris:

1. 1. • Runs the length of the femur
      • The only muscle in this group that crosses the hip joint

• • • Origin from anterior inferior iliac spine (NOT ASIS)

1. • Vasti muscles – 3

1. 1. • Vastus Medialis
      • Vastus Lateralis

• • • Vastus Intermedius- seen deep to rectus femoris

• • • All have origin from femur, some fibers take origin from intermuscular septae (medial / lateral)
    • these do not cross hip, do not act on hip

1. • These 4 muscles (Quadroceps Femoris) approach knee joint and unite into common tendon = Quadriceps tendon.

1. 1. • Inserts onto the patella (knee cap)
      • Not all of the fibers end on the patella, some continue and envelop patella (except on joint surface) and extend from its distal end and attach onto the tibial tuberosity.
      • Fibrous tissue from bone to bone is not tendon, thus these fibers from patella to tibial tuberosity are patellar ligament (is continuation of Quadriceps tendon).

1. • Action of quadriceps is to extend the knee.

1. 1. • Patella is the fulcrum
      • These are the kicking muscle (front kick)

• • • Rectus femoris: also allows weak flexion of hip joint.

1. • Special role of Vastus medialis:

• • • Distal fibers come in obliquely to join quadriceps tendon
    • This offsets the tendency for patellar dislocation due to knee extension.
      1. The patella rests between the 2 chondyles of femur. Lateral is larger, thus preventing the shift
      2. Vasta medialis offsets pull

• All muscles in anterior compartment are innervated by femoral nerve, no exceptions.

Iliacus and psosas leave abdominal pelvic cavity as common muscle (iliopsoas) before entering the thigh and attaching lesser trochanter.

Medial compartment (474): Adductor for thigh (muscles of virtue)

• Gracilis
  • Takes origin from body of pubis
  • Thin strap-like muscle
  • Extends entire length of medial thigh, crosses knee, attaches medial tibia close to insertion of sartorius (anterior) and semi-tendinosus (posterior) (all 3 insert close to eachother, the point of attachment is called Pes Anserine “goose’s foot). One muscle from each compartment.
  • Since it crosses the knee (posterior aspect) it is also a weak knee flexor
  • Primary nerve of medial compartment: Obturator
• Pectineus
  • Thin sheet like muscle
  • Origin from pubis
  • Extends laterally to attach linea aspera of femur
  • Gets innervation from femoral nerve (may get some obturator)
• Adductor longus
  1. Between Gracilis / Pectineus
  2. Origin from pubis, inserts onto shaft of femur
  3. Action is on hip joint. Often the target of a pulled groin muscle.
• Adductor brevis
  • Deep to adductor longus
  • Thin, sheet like muscle
  • Short muscle from pubis, attaches femur
  • Obturator nerve splits into anterior / posterior divisions which go on either side of adductor brevis (good landmark). Will have trunk on anterior and posterior sides.
• Obturator externis
  • From margin of obturator foramen, superior / inferior pubic rami.
  • Is a medial compartment muscle
  • Innervated by obturator nerve
  • Inserts trochanteric fossa (greater trochanter) on the femur
• Adductor magnus 2 parts:
  • Adductor part:

1. 1. • Superior fibers
      • Origin: inferior pubic ramus, ischial ramus

• • • Inserts: gluteal tuberosity, linea aspera, medial supracondylar line

• • • Nerve: obturator nerve
    • Adducts / flexes the thigh

1. • Hamstring part:

1. 1. • Vertical fibers
      • Origin: ischial tuberosity

• • • Inserts: adductor tubercle of femur

• • • Nerve: tibial part of sciatic nerve

1. • This doesn’t cross the knee joint
   • Tendon attaches along femur

1. 1. • Has small holes that allow vessels to pass through to enter the posterior compartment
      • Arteries that lie in medial compartment pierce adductor magnus to supply posterior compartment

• • • Distally, have adductor hiatus– a large gap in tendon

Nerves / Vessels (482)

Femoral Triangle:

• Boundaries:
  • Superiorly: inguinal ligament
  • Laterally: sartorius muscle
  • Medially: adductor longus
  • Floor: from medial to lateral by the adductor longus, medial pectineus, and iliopsoas
  • Roof: Fascia Lata
• Contents
  • Receives femoral nerve, artery, vein

1. 1. • When they enter the thigh, they are very superficial
      • Vovered only by fascia lata (easy to get femoral artery pulse)

1. • Artery is equidistant between ASIS and pubic tubercle
   • On medial side of artery have vein, on lateral side have nerve.
   • Vessels are enveloped in a fascial sheath that invests the femoral artery and vein ( not nerve).

1. 1. • Anterior portion of Femoral sheath is extension of transversalis fascia (anterior part) out of anterior abdominal wall.
      • Posterior part is from fascia that overlies psoas major (psoas fascia).

• • • All of this fascia is the same layer, just different extensions.

1. • Femoral nerve ends soon as it enters the thigh, only exists as femoral nerve in thigh for a few cm.

1. 1. • Terminates as sensory nerves that pierce fascia to go toward skin
      • Has motor branches that innervate anterior compartment and pectineus

• • • 2 branches leave femoral triangle and travel with vessels. These branches enter the subsartorial canal.
      1. Nerve to vastus medialis
      2. Saphenous nerve
         1. passes with vessels and parts them above knee, crosses knee joint to become subcutaneous nerve to supply medial side of leg, ankle, foot.
         2. Is pure sensory, supplies nothing in thigh, only below knee.

• • At apex, vessels pass deep to sartorius. Tunnel on deep side of sartorius = subsartorial canal, AKA adductor canal / Hunter’s canal.
• Femoral sheath has septae that run between anterior / posterior lamella of the sheath: forms 3 compartments medial to lateral
  • Most lateral is occupied by femoral artery
  • Middle has femoral vein
  • Medial compartment has some lymphatics and loose CT

• • • Has an opening into abdominal pelvic cavity and is a weak point in wall of abdominopelvic cavity.
      1. A loop of intestine may go down along medial side of femoral vein to the femoral canalà brings loop of intestine into femoral triangle = femoral hernia (female issue- canal is bigger).
      2. Will have puffiness over femoral triangleà gut may go through saphenous opening and become subcutaneous. Different from inguinal hernia (male issue)
  • Superior limit = femoral ring.

Femoral artery: 482

• Has a branch coming off in femoral triangle = deep artery of the thigh (Profundus Femoral artery)
  • Is source of blood for medial compartment as will obturator artery (branch of internal iliac)
  • Apertures in tendon of adductor magnus allow vessels to go from medial compartment to posterior compartment: these vessels are branches of profundus femoral artery = perforating arteries (4-5) which are primary blood supply for the hamstrings.
  • Distribution is to thigh, becomes smaller as approach knee.
• Profundus femoral artery gives proximal branches as well (486)
  • Near origin, gives off pair: medial / lateral circumflex arteries
  • They encircle the hip joint to provide it with collateral circulation
  • Lateral femoral circumflex is larger

1. 1. • Descending branch largest – primary supply to quadriceps
      • Ascending- around hip joint
      • Transverse branches- around hip joint

• • Medial circumflex femoral artery: supplies to head and neck of femur.
• Thus: femoral artery comes into the thigh (494)
  • Is a conduit, does not supply thigh
  • Profundus a. gives off branches that are blood supply to thigh.

1. 1. • Lateral
      • Medial branch

• • • Gives off perforating branches

• As femoral artery approaches knee (475)
  • Along with vein, pass through adductor hiatus (hole in tendon of adductor magnus)
  • Vessels go to posterior aspect of knee (477)
  • Gap between hamstring muscles shows vessels
  • Popliteal surface of femur:

1. 1. • Between epicondyles, between lines of linea aspera
      • Is the area where vessels become popliteal artery / vein

• 2 muscles in leg: Gastrocnemius (medial / lateral head) (484)
  • Creates Popliteal fossa
  • Boundaries of Popliteal fossa:

1. 1. • Superiorly: bounded by two heads of biceps femoris
      • Inferiorly: bounded by medial / lateral heads of gastrocnemius

1. • Contents of Popliteal fossa:

• • • Contains popliteal artery, vein, sciatic nerve
    • Sciatic nerve from posterior thigh unites here with the A/V.
      1. Within the popliteal fossa, sciatic nerve splits into common fibular (passes lateral) and tibial nerve (stays in midline and goes into leg deep to muscles)
      2. Thus, fascial lining is lost and 2 components branch.

• • When the knee is in full extension, fascia lata forming roof of popliteal fossa tightens.
    • Vessels are right against bone, thus pulse is hard to find here.
    • Vein is usually more superficial than artery.

• • Popliteal artery gives off about 5 branches = genicular arteries.
    • They form collateral circulation of the knee joint.
    • Flexing knee for too long may cause compression of popliteal artery, thus collateral circulation kicks in.

Posterior Thigh

Compartments:

• At mid-thigh (487)
• Deep fascia of thigh is Fascia Lata which forms boundaries of compartment
  • These are deep bands that attach to linea aspira on the femur
  • Divide thigh into 3 compartments:
• Anterior compartment: extensor compartment
  • Extension of the knee (front kick)
• Medial compartment: adductor of hip
• Posterior compartment: flexors of the knee / hip extension.
  • Also called hamstring muscles
  • As tendons approach the knee, they are thick and cord-like.
  • Have criteria:

1. 1. • Must have origin from ischial tuberosity
      • Must be innervated by tibial portion of sciatic nerve.

• (Some say): must cross hip joint and knee joint

1. 1. Three hamstring muscles in compartment:

1. Biceps femoris (long head):
   1. From ischial tuberosity, crosses posterior aspect of knee joint on lateral side
   2. attaches the head of the fibula
2. Semi-tendonosus:
   1. ½ the length is cordlike tendon.
   2. attach to tibia on medial side of the leg after crossing posterior aspect of knee joint

• Semi-membranosus:
  1. travels with semitendonosus (are bound together)
  2. is more aponeurotic
  3. crosses posterior aspect of knee joint and attaches to the tibia.

1. 1. Biceps femoris (short head)

1. A non-hamstring muscle: (477)
2. Origin from femur (linea aspira)

• Joins with long head, unites to form common tendon.

1. Nerve is common fibular portion of sciatic nerve
2. Thus, lacks 2 criteria (origin / nerve) to be hamstring.

1. 1. Are both for knee flexion and hip extension (they cross both joints)

1. Cannot get a muscle that crosses 2 joints to act maximally on both joints at same time = Active Insufficiency (is a muscular phenomenon)
2. Cannot extend hip and flex knee at same time (problem for hook kicks)

• Passive Insufficiency: cannot get muscle to stretch maximally to allow maximum range across 2 joints at same time (is a CT phenomenon).