Thigh Anatomy: Compartments and Illiopsoas

• The thigh divides into three compartments: anterior (extensor), medial (adductor), and posterior (flexor).

Compartments of the Thigh

• Anterior compartment contains pectineus, iliopsoas, sartorius, and quadriceps femoris muscles.
• The anterior compartment is supplied by the femoral nerve.
• Medial compartment contains adductor longus, adductor brevis, adductor magnus, gracilis, and obturator externus muscles.
• The medial compartment is supplied by the obturator nerve.
• Posterior compartment contains biceps femoris, semitendinosus, and semimembranosus muscles, supplied by the sciatic nerve.

Psoas Major (Illiopsoas)

• Originates from the sides of T12-L5 vertebrae and discs and the transverse processes of lumbar vertebrae.
• Inserts at the lesser trochanter of the femur.
• Receives nerve supply from the ventral rami of L1-L3, which arise from the lumbar plexus.
• Responsible for the flexion of the thigh at the hip.

Iliacus (Illiopsoas)

• Originates from the iliac crest and iliac fossa.
• Insertion is at the lesser trochanter.
• Nerve supply comes from the femoral nerve within the pelvis.
• Action is flexion of the thigh at the hip.

Sartorius

• Originates from the anterior superior iliac spine.
• Inserts on the superior part of the medial surface of the tibia (SGS).
• Nerve supply is via the femoral nerve.
• Responsible for flexion and lateral rotation of the thigh at the hip, as well as flexion of the knee.

Quadriceps Femoris

• Consists of the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius.

Rectus Femoris

• Straight head originates from the anterior inferior iliac spine.
• Reflected head originates from the groove above the acetabulum.
• Receives nerve supply from the femoral nerve.
• Produces extension of the leg at the knee joint and flexion of the hip.

Vastus Lateralis

• Originates from the greater trochanter and lateral lip of the linea aspera of the femur.
• Nerve supply is from the femoral nerve.
• Facilitates extension of the leg at the knee joint.

Vastus Medialis

• Originates from the intertrochanteric line and medial lip of linea aspera of femur.
• Nerve supply from femoral nerve.
• Causes extension of the leg at the knee joint.

Vastus Intermedius

• Originates from the anterior and lateral surfaces of the femoral shaft.
• Receives nerve supply from the femoral nerve.
• Facilitates extension of the leg at the knee joint.
• The quadriceps tendon's common insertion (tendon) goes to the patella's base.
• The patellar ligament then attaches to the tibial tuberosity.

Femoral Triangle

• Defined as a triangular area on the thigh's medial side.
• Superior (base) boundary is the inguinal ligament.
• Lateral boundary is the medial border of the sartorius.
• Medial boundary is the medial border of the adductor longus.
• The floor consists of the iliopsoas, pectineus and adductor longus from lateral to medial.

Contents of the Femoral Triangle

• Femoral nerve and branches
• Femoral sheath
• Femoral artery and branches
• Femoral vein and tributaries
• Femoral branch of the genitofemoral nerve
• Deep inguinal lymph nodes
• Lateral cutaneous nerve of the thigh

Femoral Sheath

• The femoral sheath is a downward extension of the abdominal fascia into the thigh.
• Anteriorly, it is formed by the fascia transversalis.
• Posteriorly, it is formed by the fascia iliaca.
• Consists of three compartments: lateral, intermediate, and medial.
• The lateral compartment contains femoral artery and femoral branch of genitofemoral nerve.
• The intermediate compartment contains femoral vein.
• The medial compartment, or femoral canal, contains the lymph node of Cloquet.

Femoral Nerve

• The femoral nerve is the largest branch of the lumbar plexus, originating from L2, L3, and L4 dorsal divisions.
• Emerges from the lateral border of psoas major muscle within the abdomen.
• It then passes downward between psoas and iliacus.
• It then enters the thigh behind the inguinal ligament lateral to the femoral artery but outside the femoral sheath.
• Terminates about 1½ inches (4 cm) below the inguinal ligament, dividing into anterior and posterior divisions.

Branches of the Femoral Nerve

• Muscular branches supply the muscles of the anterior compartment of the thigh.
• Articular branches extend to the knee and hip joints.
• Cutaneous branches include the intermediate and medial cutaneous nerves of the thigh.
• The saphenous nerve descends on the medial side of the knee joint and the medial side of the leg, then anterior to the medial malleolus till the medial side of the dorsum of the foot.