Sartorius Anatomy

Origin

• ASIS: Anterior Superior Iliac Spine.
• Notch: Also attaches to the upper half of the notch immediately below the ASIS.

Course

• Runs obliquely across the upper and middle thirds of the thigh.
• Moves from Lateral (ASIS) to Medial (Tibia).
• Spirals around the medial aspect of the thigh to reach the posterior aspect of the medial condyle, then curves forward.

Insertion

• Pes Anserinus: Upper part of the medial surface of the tibia.
• Arrangement: Inserts ANTERIOR and SUPERIOR to the Gracilis and Semitendinosus.
• Expansion: Sends an expansion to the capsule of the knee joint and crural fascia.

Femoral Nerve

• Roots: L2, L3.
• Branches: Usually receives 2 distinct branches from the Intermediate Cutaneous Nerve of Thigh (which pierces the muscle).
• Proprioception: High density of muscle spindles, suggesting a role in proprioceptive feedback for limb position.

The muscle is often pierced by the intermediate cutaneous nerve of the thigh.

Detailed Relations

• Anterior: Fascia Lata, Skin.
• Posterior (Deep): Iliacus, Psoas major, Rectus Femoris, Vastus Medialis, Adductor Longus/Magnus.
• Medial Border: Forms the lateral boundary of the Femoral Triangle.
• Adductor Canal: The Sartorius forms the ROOF (Anterior wall) of the canal, covering the Femoral Artery/Vein and Saphenous Nerve.

Vascular Supply

• Proximal: Branches from Circumflex Iliac arteries.
• Middle: Branches from the Femoral Artery (muscular branches).
• Distal: Branches from the Descending Genicular and Inferior Medial Genicular arteries.

This segmental supply allows for various muscular flaps (e.g., Rotation flaps for groin defects).

Palpation

• Origin: Easily palpable at the ASIS.
• Belly: Can be made prominent by asking the patient to lift the heel and cross the legs (FABER position).
• Adductor Canal: The muscle belly is the guide. The pulse of the femoral artery can be felt DEEP to the sartorius in the mid-thigh.

Surgical Marking

• A line from ASIS to the Medial Femoral Condyle approximates the course.
• The upper 1/3 forms the lateral border of the femoral triangle.
• The middle 1/3 covers the Hunter's Canal.

Identifying the medial border of the Sartorius is the key step in the anterior approach to the Femoral Artery.

Coxa Saltans (Snapping Hip) Classification

Sartorius pathology fits into the external/extra-articular types.

• External Type:
  1. Iliotibial Band (ITB): Most common. Snaps over Greater Trochanter.
  2. Gluteus Maximus: Anterior fibers snapping over GT.
• Internal Type:
  1. Iliopsoas: Snaps over Iliopectineal eminence or femoral head.
• Rare Variants:
  1. Sartorius: Snapping over the ASIS or AIIS (rare).
  2. Biceps Femoris: Long head snapping over Ischial Tuberosity.

Although Sartorius snapping is rare, it must be considered in athletes with anterior hip snapping that mimics intra-articular pathology.

Pathophysiology

• Inflammation: Of the bursa lying between the Pes Anserinus insertion and the MCL/Tibia.
• Causes: Overuse (Runners), Tight hamstrings, Obesity, Valgus deformity (Osteoarthritis).
• Association: Strongly associated with early OA of the medial compartment.

The term "Cyclist's Knee" generally refers to ITB, but "Breaststroker's Knee" can involve the Pes Anserinus (or MCL).

Clinical Presentation

• Pain: Medial aspect of proximal tibia. Worse with stairs or rising from seated.
• Swelling: Mild localized edema.
• Sign: Negative Valgus stress (excludes MCL), Negative McMurray (excludes Meniscus).

Often co-exists with medial compartment OA. Accurate localization of tenderness is key.

X-Ray

• AP/Lat Knee: Usually normal for bursitis. Assessing for OA (Osteophytes) or Stress Fracture (proximal tibia).
• Proximal Tibia Exostosis: Can irritate the overlying SGT tendons.

Ultrasound

• Diagnostic: Shows fluid filled bursa deep to SGT tendons.
• Guided Injection: Target for corticosteroid injection.

MRI

• Gold Standard.
• Shows local inflammation, tendonitis, or bursitis.
• Excludes meniscal tears or subchondral insufficiency fractures.

MRI is particularly useful to rule out a subtle tibial stress fracture in runners.

Treatment Protocol

• Physiotherapy: Focus on correcting Valgus mechanics and stretching tight adducts/hamstrings.
• Injection: Highly effective. Must be placed into the bursa, avoiding the tendon substance.

Ultrasound guidance significantly improves the accuracy of bursal injections compared to landmark-based techniques.

Pes Anserinus Harvest (ACL)

• Incision: Vertical, medial to tibial tubercle.
• Sartorius Fascia: Incise the fascia in line with the Sartorius fibers (or L-shaped incision).
• Exposure: Reflect Sartorius fascia to reveal Gracilis and Semitendinosus deep to it.
• Preservation: Usually Sartorius is PRESERVED and repaired over the tunnels.

The Sartorius acts as the "Check Rein" or covering layer. Meticulous repair of the sartorius fascia prevents hematoma formation and assists with healing.

Adductor Canal Exploration

• Indication: Vascular bypass, Saphenous nerve release.
• Landmark: Medial border of Sartorius.
• Technique: Retract Sartorius LATERALLY (usually) or medially (depending on exposure need).
• Roof: Incise the subsartorial fascia to access the vessels.
• Nerve: Identify Saphenous nerve crossing from lateral to medial over the artery.

Careless retraction can injure the nerve to Vastus Medialis which runs with the Saphenous nerve.