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Anterior Compartment of the Thigh Muscles Anatomy
Anterior Compartment of the Thigh Muscles Anatomy
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The front part of the thigh, also called the anterior compartment, contains a group of muscles mainly responsible for extending the leg at the knee and flexing the thigh at the hip.Β
These muscles are essential for everyday movements such as walking, running, climbing stairs, and standing up from a seated position. They help stabilize the hip and knee joints and support much of the bodyβs weight during movement.
There are five main muscles in the anterior thigh compartment:Β
Sartorius
Quadriceps Femoris group (rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius).Β
Another important muscle near the front of the hip, the iliopsoas, also helps move the thigh but acts differently than most of the others. Together, these muscles play a key role in lower body movement, balance, and posture.
Sartorius
Sartorius
The sartorius is the longest muscle in the human body. It runs diagonally across the thigh from the outer hip to the inner knee, forming an S-shaped line.
Β Itβs located more superficially than other thigh muscles and helps with several complex movements, including crossing one leg over the other.
Origin: Anterior superior iliac spine (ASIS).
Insertion: Upper medial surface of the tibia.
Innervation: Femoral nerve.
Quadriceps Femoris
Quadriceps Femoris
The quadriceps femoris is one of the strongest muscle groups in the body. It includes four muscles: rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. Together, they form the main bulk of the front thigh. All four insert into the patella (kneecap) via the quadriceps tendon, which connects to the tibial tuberosity through the patellar ligament. Their main job is to extend the knee.
Vastus Lateralis
The vastus lateralis, from the greater trochanter and lateral lip of the linea aspera, extends the knee and stabilizes the patella.
Vastus Intermedius
The vastus intermedius, from the front and sides of the femoral shaft, extends the knee and stabilizes the patella.
Vastus Medialis
The vastus medialis, from the intertrochanteric line and medial lip of the linea aspera, extends the knee and stabilizes the patella.
Rectus Femoris
The rectus femoris, from the anterior inferior iliac spine and the area above the acetabulum, extends the knee and flexes the hip (itβs the only one of the four that crosses both joints).
Innervation: All by the femoral nerve.
Pectineus
Pectineus
The pectineus is a short, flat muscle that sits near the top of the inner thigh and helps form the floor of the femoral triangle. It helps bring the leg inward (adduction) and assists in hip flexion.
Origin: Pectineal line of the pubis.
Insertion: Pectineal line of the femur (just below the lesser trochanter).
Innervation: Mainly the femoral the nerve, sometimes also the obturator nerve.
Inner Hip Muscles
Inner Hip Muscles
Inner hip muscles are a group of smaller but very important muscles found deep inside the pelvis and upper thigh region. They connect the pelvis to the femur (thigh bone) and are mainly responsible for controlling the movement of the hip joint. Together, these muscles help you rotate, lift, and stabilize your thigh during activities like walking, running, jumping, and even sitting upright.
Although they are often overlooked compared to the larger thigh muscles, the inner hip muscles are crucial for posture and balance. They keep the head of the femur securely positioned inside the hip socket (acetabulum), preventing dislocation and ensuring smooth movement of the leg.
Quick Reference Table: Muscle Name, Origin, Insertion & Innervation
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Iliacus and Psoas Major (Iliopsoas)
The iliacus and psoas major together form the iliopsoas, the most powerful hip flexor in the body. These muscles start from the pelvis and lower spine and attach to the lesser trochanter of the femur.Β
They pull the thigh upward and slightly outward, allowing you to lift your leg when walking, climbing stairs, or running. They also help bend the trunk forward when your legs are fixed in place.
Origin: Psoas Major - transverse processes and bodies of T12βL5 vertebrae; Iliacus -Β Iliac fossa and anterior inferior iliac spine.
Insertion: Lesser trochanter of the femur.
Innervation: Iliacus - femoral nerve; Psoas Major - lumbar nerves (L1-L3).
Psoas Minor
The psoas minor is a small muscle; itβs missing in about half of people. When present, it lies in front of the psoas major and assists slightly in bending the trunk forward (flexion). It doesnβt play a major role in hip movement.
Origin: Vertebral bodies of T12 and L1.
Insertion: Pectineal line of the pubic bone.
Innervation: Anterior rami of L1 spinal nerve.
Obturator Externus
The obturator externus is located on the outer surface of the pelvis. It helps rotate the thigh outward and stabilizes the hip joint by keeping the head of the femur securely in the socket. This muscle is especially active when turning your leg outward, like when crossing one leg over the other while sitting.
Origin: Anterior surface of the obturator membrane, bony boundaries of the obturator foramen.
Insertion: Trochanteric fossa of the femur.
Innervation: Obturator nerve (L3, L4).
Piriformis
The piriformis is responsible for lateral rotation and abduction of the thigh.
Origin: From the front of the sacrum to the greater trochanter.
Insertion: Greater trochanter of the femur.
Innervation: Nerve to piriformis (branch of the sacral plexus).
Obturator Internus
The obturator internus is responsible for lateral rotation and abduction.
Origin: From the inner surface of the pelvis (obturator foramen) to the greater trochanter.
Insertion: Medial surface of the greater trochanter of the femur.
Innervation: Nerve to the obturator internus (branch of the sacral plexus).
Quadratus Femoris
The quadratus femoris is responsible for the lateral rotation of the thigh.
Origin: From the ischial tuberosity to the intertrochanteric crest.
Insertion: Intertrochanteric crest of the femur.
Innervation: Nerve to quadratus femoris (branch of the sacral plexus).
Gemelli
The gemelli (superior and inferior) are responsible for lateral rotation and abduction.
Origin: Superior gemellus from the ischial spine; inferior gemellus from the ischial tuberosity; both attach to the greater trochanter.
Insertion: Medial surface of the greater trochanter of the femur.
Innervation: Superior gemellus, nerve to obturator internus (branch of the sacral plexus); inferior gemellus, nerve to quadratus femoris (branch of the sacral plexus).
Need a recap? Take a look at the Anterior Compartment of the Thigh anatomy notes here.
Need a recap? Take a look at the Anterior Compartment of the Thigh anatomy notes here.
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References
References
Gray, H. (2009). Anatomy of the human body, part 2 (LibriVox Volunteers, Narr.) [Audiobook]. LibriVox. https://librivox.org/anatomy-of-the-human-body-part-2-by-henry-gray/ (Original work published 1858)
J Gordon Betts, Desaix, P., Johnson, E., Johnson, J. E., Korol, O., Kruse, D., Poe, B., Wise, J., Womble, M. D., & Young, K. A. (2013). Anatomy & physiology. Openstax College, Rice University. https://openstax.org/details/books/anatomy-and-physiology
Based on OpenStax, Anatomy and Physiology (2013), licensed under CC BY 4.0.
Access for free at https://openstax.org/books/anatomy-and-physiology/pages/1-introduction.
Content paraphrased; adaptations were made.
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