Thigh Muscles

The thigh is the part of the lower limb that extends from the hip to the knee. It contains some of the body’s largest and strongest muscles, which not only stabilize the legs but also play a vital role in moving them. By supporting the upper body through their connection with the hips, these muscles make everyday activities such as walking, running, and climbing possible.

Fascial Compartments of the Thigh

There are roughly 15 individual muscles surrounding the thigh region that give it shape and function. Based on their location, these muscles are organized into three fascial compartments: anterior, medial, and posterior. Muscles at the front of the thigh belong to the anterior compartment, those along the inner thigh and groin make up the medial compartment, and those at the back of the thigh are in the posterior compartment.

Intermuscular Septa That Separate the Three Compartments

The thigh shows a clear division into these three compartments in a cross-section. The compartments are arranged around the femur and are separated from one another by three thick layers of deep fascia, called intermuscular septa. 

• Lateral intermuscular septum: Found on the lateral (outer) side of the thigh, it separates the anterior compartment from the posterior compartment.
• Medial intermuscular septum: Found on the medial (inner) side of the thigh, it separates the anterior compartment from the medial compartment.
• Posterior intermuscular septum: Found at the back of the thigh, it separates the posterior compartment from the medial compartment.

The entire structure is surrounded by the fascia lata or the deep fascia of the thigh that marks the outer boundaries of these compartments.

Muscles in the Anterior Compartment of the Thigh

These muscles originate from the hip bone and/or femur, cross the knee joint, and insert into the knee and lower leg bones, typically the patella and tibia.

Here are the muscles located at the front of the thigh: 

• Sartorius
• Articularis genus
• Quadriceps femoris (a four-headed muscle group)
  • Rectus femoris
  • Vastus lateralis
  • Vastus intermedius
  • Vastus medialis

The iliopsoas muscle complex, formed by the iliacus and psoas major muscles, is sometimes considered part of the anterior compartment, as it contributes to moving the thigh at the hip joint. However, anatomically, it is located in the posterior abdominal wall.

Function: These muscles flex the hip joint (sartorius, rectus femoris) and extend the knee joint (quadriceps femoris group).

Nerve Supply: Femoral nerve (L2-L4).

Blood Supply: From branches of the femoral artery.

Muscles in the Medial Compartment of the Thigh

These muscles arise from the hip bone, cross the hip joint, and insert into the femur, except the gracilis, which continues past the knee to the tibia.

Here are the muscles located on the inner thigh:

• Gracilis
• Pectineus
• Adductor brevis
• Adductor longus
• Adductor magnus

The obturator externus lies in the medial compartment anatomically, but functions with the posterior compartment muscles.

Function: These muscles make up the hip adductor group and bring the thighs toward the midline at the hip joint.

Nerve Supply: Obturator nerve (L2-L4).

Blood Supply: Obturator artery; most individual muscles receive additional blood supply from branches of the deep femoral artery.

Muscles in the Posterior Compartment of the Thigh (Hamstring Group)

These muscles all originate from the ischial tuberosity in the hip bone, cross both the hip and knee joints, and insert into the tibia and/or fibula. The only exception is the short head of the biceps femoris, which originates from the femur.

Here are the muscles located at the back of the thigh:

• Biceps femoris
• Semitendinosus
• Semimembranosus

Function: Acting as the hamstring group, these muscles flex the knee and also work together with the gluteus maximus to extend the hip joint.

Nerve Supply: Tibial branch (L4-S3) of the sciatic nerve.

Blood Supply: From branches of the inferior gluteal artery and perforating branches of the deep femoral artery.