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The Gemellus Muscles

The word “gemellus” comes from the Latin word “geminus,” meaning “twin.” True to their name, there are two gemellus muscles:

  1. Superior gemellus
  2. Inferior gemellus

These small, triangular muscles are located in the hip region, specifically in the buttocks area. They’re part of a group of muscles known as the lateral rotators of the hip.

Anatomy and Location

The gemellus muscles are situated in a strategic position:

  • The superior gemellus originates from the ischial spine of the pelvis.
  • The inferior gemellus originates from the ischial tuberosity and the lateral obturator ring.

Both muscles insert into the medial surface of the greater trochanter of the femur (thighbone), alongside the tendon of the obturator internus muscle.

See Also: Hip Muscles Anatomy
Gemellus Muscles insertion

Function and Action

Despite their small size, the gemellus muscles play several important roles:

  1. Lateral Rotation: Their primary function is to rotate the thigh laterally (external rotation).
  2. Hip Abduction: They assist in abducting the flexed thigh (moving it away from the body’s midline).
  3. Stabilization: They help stabilize the hip joint during movement.

Interestingly, these muscles work in close cooperation with the obturator internus muscle. Together, they form what’s known as the “triceps coxae” or “triceps of the hip.”

Innervation and Blood Supply

The gemellus muscles receive their nerve supply from different sources:

  • The superior gemellus is innervated by the nerve to the obturator internus (from the sacral plexus, L5-S1).
  • The inferior gemellus is innervated by the nerve to the quadratus femoris.

Both muscles receive their blood supply primarily from the inferior gluteal artery.

Superior and Inferior gemellus muscles
OriginIschial spine
InsertionMedial surface of greater trochanter of femur, in common with obturator internus
InnervationNerve to the obturator internus and superior gemellus a branch of the sacral plexus (L5, S1)
Blood SupplyInferior gluteal artery
ActionRotates the thigh laterally (external rotation of the thigh)
Also helps abduct the flexed thigh
Superior Gemellus Muscle Anatomy
OriginPosterior portions of ischial tuberosity and lateral obturator ring
InsertionMedial surface of greater trochanter of femur, in common with obturator internus
InnervationNerve to the quadratus femoris and inferior gemellus
Blood SupplyInferior gluteal artery
ActionRotates the thigh laterally (external rotation of the thigh)
Also helps abduct the flexed thigh
Inferior Gemellus Muscle Anatomy

Clinical Significance

While rarely injured in isolation due to their small size and protected location, the gemellus muscles can be affected in conditions involving the hip rotators or sciatic nerve. Strengthening these muscles can contribute to improved hip stability and function, which is beneficial for various activities and sports.

Gemelli-obturator syndrome involves dynamic compression of the sciatic nerve due to stretching of the gemelli-obturator complex. The anatomical relationship between the sciatic nerve (coursing deep to the piriformis and superficial to the triceps coxae muscles) creates potential for nerve compression, resulting in sciatic pain

The gemelli muscles, components of the triceps coxae, have significant implications in the posterior surgical approach to the hip, also known as the Kocher-Langenbeck approach.

References & More

  1. Clinically Oriented Anatomy – 8th Edition
  2. Lezak B, Massel DH. Anatomy, Bony Pelvis and Lower Limb, Gemelli Muscles. [Updated 2023 Aug 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: Pubmed
  3. Balius R, Susín A, Morros C, Pujol M, Pérez-Cuenca D, Sala-Blanch X. Gemelli-obturator complex in the deep gluteal space: an anatomic and dynamic study. Skeletal Radiol. 2018 Jun;47(6):763-770. PubMed
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