What is the longest muscle in the body?

Sartorius Muscle Anatomy: Origin, Insertion,  & ActionSartorius Muscle Anatomy Study
Origin: Inferior portion of the anterior superior iliac spine and the area just below it plus the sacrum
Insertion: Upper medial surface of tibial shaft at the tibial flare
Action: Assists with hip flexion, knee flexion, medial rotation of the knee, lateral rotation of the hip
Synergist:  Iliopsoas, Pectineus, Tensor fasciae latae, Adductor brevis.

Primary Actions of the Sartorius:

• The Sartorius is not a prime mover and does not have a primary action, who knew?

Secondary Actions of the Sartorius:1. Assists with flexion of the thigh at the hip

• Agonists: Psoas Major, Iliacus
• Antagonists: Gluteus Maximus, Semitendinosus, Semimembranosus, Biceps Femoris (long head), adductor magnus (posterior part)

2. Assists with external rotation of the thigh at hip

• Agonists: Obturator Internus, Obturator Externus, Gemellus Superior, Gemellus Inferior, Quadratus Femoris
• Antagonists: Tensor Fasciae Latae, Gluteus Minimus (anterior fibers), Gluteus Medius (anterior fibers)

3. Assists with abduction of the thigh at the hip

• Agonists: Gluteus Maximus (upper fibers), Gluteus Medius, Gluteus Minimus
• Antagonists: Adductor Longus, Adductor Brevis, Adductor Magnus

4. Assists with flexion of the knee

• Agonists: Biceps Femoris, Semitendinosus, Semimembranosus
• Antagonists: Vastus Lateralis, Vastus Intermedius, Vastus Medialis, Rectus Femoris

5. Assists with internal rotation of the knee when flexed

• Agonists: Popliteus, Semitendinosus, Semimembranosus
• Antagonists: Biceps Femoris

And yes, the sartorius is the longest muscle in the body.

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