Sartorius Muscle: Anatomy, Origin, Insertion, Nerve Supply, Relations, Function, MRI & CT Imaging

Topic

Sartorius muscle

The sartorius is the longest muscle in the human body, running obliquely across the anterior thigh. It extends from the anterior superior iliac spine to the medial aspect of the tibia. Its superficial, strap-like course gives the thigh its diagonal contour. The sartorius is part of the anterior compartment of the thigh and plays a key role in complex movements of the hip and knee, especially those involving crossing the legs.

It has important surgical and radiological relevance due to its superficial location, role in pes anserinus formation, and utility as a flap in reconstructive surgery.

Synonyms

Tailor’s muscle
Longest muscle of the body
Anterior thigh strap muscle

Origin, Course, and Insertion

Origin:
- Arises from the anterior superior iliac spine (ASIS) and adjacent notch below it
Course:
- Runs inferomedially across the anterior thigh in a spiral-like path
- Lies superficial to the quadriceps, adductors, and other thigh muscles
- Forms the lateral border of the femoral triangle proximally and the roof of the adductor canal distally
Insertion:
- Inserts into the medial surface of the proximal tibia as part of the pes anserinus, alongside gracilis and semitendinosus tendons

Relations

Anteriorly: Subcutaneous tissue and skin
Posteriorly: Quadriceps femoris proximally, adductors and gracilis distally
Laterally: Tensor fasciae latae and rectus femoris
Medially: Adductor longus, gracilis, semitendinosus

Nerve Supply

Femoral nerve (L2–L4)

Arterial Supply

Femoral artery (muscular branches)
Lateral circumflex femoral artery
Descending genicular artery

Venous Drainage

Venous drainage into the femoral vein via the great saphenous and muscular tributaries

Function

Flexion of the hip joint
Abduction and external rotation of the thigh
Flexion of the knee joint
Contributes to combined actions such as sitting cross-legged (“tailor position”)

Clinical Significance

Commonly used in reconstructive surgery as a flap due to its length and vascularity
Involved in pes anserinus bursitis, leading to medial knee pain
Can be strained in athletes with forceful hip or knee movements
Serves as a surface landmark in femoral triangle and adductor canal approaches

MRI Appearance

T1-weighted images:

Muscle shows low-to-intermediate signal intensity
Fatty infiltration or chronic degeneration may appear bright

T2-weighted images:

Low-to-intermediate baseline signal intensity
Acute strain or edema shows bright signal intensity

STIR (Short Tau Inversion Recovery):

Baseline signal low-to-intermediate
Inflammation, bursitis near pes anserinus, or acute injury appears bright

Proton Density Fat-Sat (PD FS):

Normal muscle shows low-to-intermediate signal
Pathology appears with localized or diffuse bright signal

T1 Fat-Sat Post-Contrast:

Normal muscle enhances mildly and evenly
Pathological states show heterogeneous or rim enhancement, depending on etiology

CT Appearance

Non-Contrast CT:

Appears as a homogeneous soft tissue density running obliquely across anterior thigh
Acute hematoma appears hyperdense
Chronic fatty change shows low attenuation

Post-Contrast CT:

Mild uniform enhancement in normal muscle
Inflammatory, neoplastic, or traumatic pathology shows more intense, heterogeneous enhancement
Abscess demonstrates rim enhancement with central low density

MRI image