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Rectus femoris muscle

The rectus femoris is one of the four muscles of the quadriceps femoris group, located in the anterior compartment of the thigh. It is unique among the quadriceps because it crosses both the hip and knee joints, acting as a flexor of the hip and an extensor of the knee. It is a long, fusiform muscle situated superficially, making it an important surface landmark.

It plays a vital role in walking, running, kicking, and jumping, and is commonly involved in sports-related injuries such as strains and tendinopathies.

Synonyms

  • Straight head of quadriceps femoris

  • Rectus of the thigh

  • Quadriceps rectus muscle

Origin, Course, and Insertion

  • Origin:

    • Straight head: Anterior inferior iliac spine (AIIS)

    • Reflected head: Superior rim of the acetabulum and hip joint capsule

  • Course:

    • The two heads unite to form a thick, fusiform belly

    • The muscle descends vertically in the anterior thigh, lying superficial to the vastus intermedius

    • Distally, it joins the other quadriceps muscles to form the quadriceps tendon

  • Insertion:

    • Inserts via the quadriceps tendon into the base of the patella

    • Continues through the patellar ligament to attach to the tibial tuberosity

Relations

  • Anteriorly: Subcutaneous tissue and skin of the anterior thigh

  • Posteriorly: Vastus intermedius muscle

  • Laterally: Vastus lateralis

  • Medially: Vastus medialis

  • Superiorly: Hip joint capsule and iliacus

  • Inferiorly: Quadriceps tendon and patella

Nerve Supply

  • Femoral nerve (L2–L4)

Arterial Supply

  • Lateral circumflex femoral artery (ascending and descending branches)

  • Femoral artery (muscular branches)

  • Profunda femoris artery (contributions)

Venous Drainage

  • Venous blood drains into the lateral circumflex femoral vein, profunda femoris vein, and ultimately into the femoral vein

Function

  • Extends the leg at the knee joint (as part of the quadriceps group)

  • Flexes the thigh at the hip joint

  • Stabilizes the hip and knee during walking and running

  • Provides explosive power during jumping and kicking

Clinical Significance

  • Frequently injured in sports, especially during sprinting or kicking

  • Involved in rectus femoris tendinopathy and quadriceps tendon rupture

  • Important in gait biomechanics and rehabilitation following knee or hip surgery

  • Target in intramuscular injections (though vastus lateralis is preferred)

MRI Appearance

T1-weighted images:

  • Muscle shows low-to-intermediate signal intensity

  • Chronic fatty infiltration or degeneration shows bright signal

T2-weighted images:

  • Normal baseline signal is low-to-intermediate

  • Acute injury, edema, or strain shows bright signal

STIR (Short Tau Inversion Recovery):

  • Muscle demonstrates low-to-intermediate baseline signal

  • Pathology such as strain or inflammation shows bright signal

Proton Density Fat-Sat (PD FS):

  • Low-to-intermediate baseline signal

  • Acute injury or tendinopathy appears as localized bright signal

T1 Fat-Sat Post-Contrast:

  • Normal muscle enhances mildly and uniformly

  • Pathology shows heterogeneous or rim enhancement depending on lesion type

CT Appearance

Non-Contrast CT:

  • Appears as homogeneous soft tissue density in anterior thigh

  • Acute hematoma may appear as hyperdense region

  • Chronic fatty degeneration may appear as low-attenuation streaks

Post-Contrast CT:

  • Normal muscle shows mild homogeneous enhancement

  • Pathologic changes (inflammatory or neoplastic) show irregular or intense enhancement

  • Abscess appears as central low density with peripheral rim enhancement

MRI image

Rectus femoris muscle MRI axial anatomy image-img-00000-00000_00001 - Copy

MRI image

Rectus femoris muscle MRI axial anatomy image-img-00000-00000 - Copy

CT image

Rectus femoris muscle CORONAL

CT image

Rectus femoris muscle ct axial anatomy image-img-00000-00000

CT image

Rectus femoris muscle ct axial anatomy image-img-00000-00000_00001

CT image

Rectus femoris muscle ct