The muscles of the anterior compartment of the thigh are an important group of muscles that mostly function to extend the lower limb at the knee joint. This group of muscles is innervated by the femoral nerve (L2-L4), and is fed by the femoral artery. In this article, we will delve into the anatomy of the muscles of the anterior thigh, their actions, attachments and clinical correlations.
The iliopsoas comes as a two-muscle package, the psoas major and iliacus. These muscles originate from the pelvis and pass underneath the inguinal ligament into the anterior compartment of the thigh; where they’re then amalgamated into one common tendon. Unlike the majority of other anterior thigh muscles, the iliopsoas does not contribute to the extension of the leg at the knee joint.
Attachments: The psoas major has its origins from the lumbar vertebrae, while the iliacus has its origins from the iliac fossa of the pelvis. They both teriminate at the lesser trochanter of the femur.
Actions: Flexion of the thigh at the hip joint.
Innervation: The psoas major is innervated by the anterior rami of L1 to L3 of the spinal nerve, while the iliacus is innervated by the femoral nerve.
The quadriceps femoris is a formidable group of muscles that consist of the three vastus muscles and rectus femoris. This group of muscles forms the major bulk of the anterior compartment of the thigh, and is one of the most powerful muscles in the human body. All four components of the quadriceps femoris insert onto the patella via the quadriceps tendon, which then further attaches to the tibial tuberosity via the patella ligament.
Proximal Attachment: Originates from the greater trochanter and the lateral lip of the linea aspera of the femur.
Actions: Extension of the knee joint. It also helps to stabilize the patella.
Innervation: Innervated by the femoral nerve.
Proximal Attachment: Originates from the anterior and lateral surfaces of the femoral shaft.
Actions: Extension of the knee joint. It also helps to stabilize the patella.
Innervation: Innervated by the femoral nerve.
Proximal Attachment: Originates from the intertrochanteric line and medial lip of the linea aspera of the femur.
Actions: Extension of the knee joint. It also helps to stabilize the patella.
Innervation: Innervated by the femoral nerve.
Attachments: Originates from the anterior inferior iliac spine and the ilium of the pelvis. It attaches to the patella via the quadriceps femoris tendon.
Actions: Extension of the knee joint and flexion of the hip joint (it is the only muscle of the quadriceps group to cross both the hip and knee joints).
Innervation: Femoral nerve.
The sartorius muscle is the longest muscle in the body. It is long and slender, lying supercially to the other muscles in the thigh, and runs in the inferomedial direction.
Attachments: Originates from the anterior superior iliac spine and attaches to the superior, medial surface of the tibia.
Actions: At the hip joint, it is a flexor, abductor and lateral rotator. At the knee joint, it is also a flexor.
Innervation: Femoral nerve.
The pectineus is a flat, quadrangular-shaped muscle and is positioned at the lower margin of the femoral triangle.
Attachments: Originates from the pectineal line of the pubis bone. It attaches to the pectineal line on the posterior aspect of the femur, immediately inferior to the lesser trochanter.
Actions: Adduction and flexion of the hip joint.
Innervation: Femoral nerve. It may also receive a branch from the obturator nerve.
The Anterior Compartment of the Thigh contains the following muscles: Iliopsoas, Quadriceps Femoris, Vastus Lateralis, Vastus Intermedius, Vastus Medialis, Rectus Femoris, and Sartorius. The iliopsoas is responsible for flexion of the thigh at the hip joint and is innervated by the anterior rami of L1-3, while the iliacus is innervated by the femoral nerve. It inserts onto the pectineal line, which is located on the posterior aspect of the femur, immediately inferior to the lesser trochanter. Its action is adduction and flexion at the hip joint.
The quadriceps femoris is one of the most powerful muscles found in the body and is composed of four individual muscles - the three vastus muscles and the rectus femoris, collectively forming a bulk of the anterior thigh. All four muscles insert onto the patella via the quadriceps tendon, which in turn is attached to the tibial tuberosity by the patella ligament.
The sartorius is the longest muscle found in the human body and runs across the thigh in a inferomedial direction. It is more superficially placed than the other muscles in the leg and is positioned between the other muscles in the leg. It originates at the anterior superior iliac spine and attaches to the superior, medial surface of the tibia. At the hip joint, it is a flexor, abductor and lateral rotator. At the knee joint, it is also a flexor and is innervated by the femoral nerve.
The pectineus is a flat, quadrangular-shaped muscle which contributes to the floor of the femoral triangle. It originates from the pectineal line of the pubis bone.
The quadriceps femoris muscle can be used to test the femoral nerve in cases of suspected nerve palsy. This is performed by positioning the patient supine, with the knee slightly flexed. The patient is then asked to extend the leg (at the knee) against resistance. If the femoral nerve is damaged, contraction of the quadriceps femoris will be absent, demonstrating the significance of this muscle group in testing for nerve damage.
The combination of the four individual muscle groups that make up the quadriceps femoris allows for powerful and coordinated movement at the knee joint, as well as secondary stabilizing of the patella. In testing for nerve damage, they can also be used to assess the functionality of the femoral nerve, which can allow for a more accurate diagnosis and subsequent treatment plan.
