By Elizabeth A. Murray, Mount St. Joseph University
The thigh has three compartments of muscles that surround the femur—anterior, medial, and posterior. The anterior compartment contains the four muscles of the quadriceps femoris group, as well as four other muscles, but some consider the tensor muscle of the fascia lata with the gluteal region.
Iliopsoas
The most proximal anterior compartment muscle is psoas major which is the muscle posterior to and around which the lumbar plexus forms and distributes in the posterior abdominal wall. Psoas major originates from the 12th thoracic vertebra and the five lumbar vertebrae and ends up in a dual insertion on the lesser trochanter of the femur.
It is called dual insertion because a second muscle—the iliacus—takes origin from the iliac fossa of the hip bone, blends with the psoas major, and together they insert on the lesser trochanter—the two muscles are collectively called the iliopsoas. Because psoas major originates on the lumbar spine, it can help flex the trunk at the low back, whereas iliacus cannot. But both cross the anterior aspect of the hip joint, so together they flex the hip.
In terms of innervation, iliacus is supplied by the femoral nerve itself, while psoas major is supplied by small segmental branches off the ventral rami of the lumbar plexus, due to its proximity near the midline of the body.
Psoas Minor
Psoas minor is found in very few people. But when present, psoas minor appears as a small version of psoas major sitting on the major’s anterior surface.
It typically originates from T12 and L1 only and inserts on the anterior pelvic bone near where the ilium and pubis meet. It doesn’t insert with the iliopsoas.
This article comes directly from content in the video series How We Move: The Gross Anatomy of Motion. Watch it now, on Wondrium.
Sartorius
Once within the anterior thigh, the most superficial, most obvious muscle is the sartorius—the longest muscle in the body.
Sartorius originates from the anterior superior iliac spine and then takes an oblique course to attach to the medial aspect of the proximal tibia, so it crosses both the hip joint and the knee joint. Its attachment to the medial tibia is in a spot known as the pes anserine, from the Latin for the “goose’s foot”.
Sartorius is supplied by the femoral nerve, and is used when you cross your legs to put your lateral leg on top of your opposite knee. In words, what’s happening during that motion is that you are flexing, abducting, and laterally rotating at the hip joint, while flexing and slightly mediately rotating your knee joint.
The name sartorius comes from the Latin for “tailor”, since in the past, tailors would sit cross-legged with their fabric in their lap while they worked.
Tensor of the Fascia Lata
Another muscle that—in a not-so-obvious sense—could be said to cross both the hip and the knee is the tensor of the fascia lata. In a cadaver, it appears like a pocket or packet of muscle within the anterior and superior aspect of the iliotibial tract.
The muscle belly originates from the lateral edge of the anterior superior iliac spine and a pronounced region on the lateral ilium known as the iliac tubercle and inserts on the iliotibial tract or IT band—which crosses the knee. But, the muscle belly really only acts on the hip joint and to tighten the iliotibial tract, thereby supporting the hip, thigh, and lateral knee.
Because it is lateral to the hip joint, the tensor of the fascia lata can assist in hip abduction, and because it’s anteriorly placed, it can assist in hip flexion, as well as medial rotation of the hip.
Quadriceps Femoris
The last four muscles in the anterior thigh constitute the quadriceps femoris group: rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. Though they all have different origins, all four of these muscles converge on a single tendon that crosses the anterior aspect of the knee joint. It’s in this tendon that the patella forms, then the tendon—now better called a ligament—continues distal to the knee joint to attach to the tibial tuberosity.
So, the quadriceps tendon connects the four quad muscles to the patella, then the continuing portion attaches the patella to the tibial tuberosity—it connects bone to bone—so is anatomically referred to as the patellar ligament.
Rectus Femoris
The rectus femoris also crosses the hip joint—and is the only one of the quads that does. It originates on the anterior inferior iliac spine and partly on the rim of the acetabulum, crosses the anterior hip joint, and then inserts by the patellar ligament onto the tibial tuberosity, crossing the anterior knee joint.
It is used when thigh flexion and knee extension are needed together, like when kicking a ball. The other three members of the quadriceps group all originate from the femur itself, and since they don’t cross the hip, can only act in knee extension.
Vastus Lateralis, Medialis, Intermedius
Vastus lateralis originates along the intertrochanteric line, the greater trochanter’s inferior border, the gluteal tuberosity, and all along the lateral aspect of the linea aspera.
So, although it is a member of the anterior compartment of the thigh, the origin of vastus lateralis begins posteriorly on the femur, it passes deep to the iliotibial tract, and joins the other three quadriceps femoris muscles to insert on the tibial tuberosity. It is the largest muscle in the body and can be seen and felt all along the lateral thigh.
The vastus medialis originates off the intertrochanteric line and medial aspect of the linea aspera, but the bulge of its muscle appears much closer to the knee, where it joins the quadriceps tendon.
The final member of the quads, the vastus intermedius is deep to rectus femoris. Vastus intermedius takes origin all along the anterior and lateral proximal two-thirds of the femur, including as far posteriorly as the linea aspera, and joins the other three members of the quadriceps femoris group to cross the anterior knee and attach to the tibial tuberosity.
Common Questions about the Anterior Compartment Muscles of the Thigh
The anterior compartment contains the four muscles of the quadriceps femoris group, as well as four other muscles, but some consider the tensor muscle of the fascia lata with the gluteal region.
The last four muscles in the anterior thigh constitute the quadriceps femoris group: rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius.
Apart from the quadriceps femoris group, there are psoas major, iliacus, psoas minor, sartorius, and tensor of the facia lata constituting the anterior compartment.
