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Inferior Gemellus Muscle Anatomy

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Origin
  • Ischial tuberosity
Insertion
  • Medial surface of the greater trochanter, near the trochanteric fossa, via the obturator internus tendon
Action
  • Lateral rotation of the hip
  • Assists with abduction when the hip is flexed
Innervation
  • Nerve to quadratus femoris (L5, S1)
Blood Supply
  • Inferior gluteal and medial circumflex femoral arterial contributions
  • Descriptions vary between sources
Last updated: Estimated Reading Time: 5 min

Location & Overview

The inferior gemellus is one of the two gemellus muscles. The inferior gemellus is located inferior to (below) the superior gemellus and is also superior to (above) the quadratus femoris muscle. Both gemellus muscles are collectively known as the gemelli muscles, and they are two of the six external rotator muscles of the gluteal region. The other four muscles are the obturator externus, obturator internus, quadratus femoris, and piriformis. Both gemelli muscles connect to the obturator internus muscle via a conjoined tendon. The combination of these three muscles is sometimes referred to as the ‘triceps coxae’.[1,2]

Inferior gemellus muscle, posterior view
Here, we can see the inferior gemellus muscle from a posterior view.
Deep six hip external/lateral rotators
Pictured here are the deep six hip external rotator muscles: the piriformis, superior gemellus, inferior gemellus, obturator internus, obturator externus, and quadratus femoris. These muscles play an important role in stabilizing the hip joint and facilitating hip lateral rotation.

Origin & Insertion

The inferior gemellus originates from the ischial tuberosity. Its tendon blends with the obturator internus tendon and inserts on the medial surface of the greater trochanter, near the trochanteric fossa. It sits inferior to the obturator internus and superior to the quadratus femoris, helping reinforce the obturator internus tendon region.[3,4]

Inferior gemellus origin marked in red
Here, we can see the origin of the inferior gemellus muscle marked in red on the ischial tuberosity.
Inferior gemellus insertion marked in blue
Here, we can see the insertion of the inferior gemellus muscle marked in blue on the medial surface of the greater trochanter, near the trochanteric fossa.

Action & Function

The primary action of the inferior gemellus is lateral (external) rotation of the hip joint. Additionally, when the hip is flexed, the muscle can also aid in abduction of the hip. However, it is worth noting that the force the gemelli muscles provide for abduction is significantly weaker than that of larger muscles, such as the gluteal muscles.[1,2]

Image of a person demonstrating the movement of external rotation.
This image shows an example of hip external rotation, which involves rotating the leg from the hip joint outward (laterally). External rotation is also referred to as lateral rotation. The opposite of external rotation (lateral rotation) is internal rotation (medial rotation). External (lateral) rotation of the hip joint is the primary action of the inferior gemellus.
Image of a person demonstrating the movement of hip abduction.
This image shows an example of hip abduction, which involves moving the leg out to the side (laterally). The opposite of hip abduction is hip adduction. The inferior gemellus can assist with hip abduction, but only when the hip is flexed.

Innervation

The inferior gemellus is innervated by the ‘nerve to quadratus femoris’, which originates from the spinal roots of L5 and S1. This nerve also innervates the quadratus femoris muscle. The nerve passes through the greater sciatic foramen as it leaves the pelvic cavity. It also passes underneath the piriformis muscle as it enters the gluteal region.[1,2]

Nerve to quadratus femoris
This image shows the nerve to quadratus femoris, which innervates the inferior gemellus muscle.

Blood Supply

The inferior gemellus has varying blood-supply descriptions. Some descriptions list the inferior gluteal artery as supplying both gemelli, while others list the inferior gemellus as supplied mainly by the medial circumflex femoral artery.[4,5] This discrepancy is anatomically plausible because the deep branch of the medial circumflex femoral artery passes anterior to the conjoint tendon of the inferior gemellus, obturator internus, and superior gemellus, while the inferior gluteal artery supplies neighboring deep gluteal muscles and participates in nearby posterior hip arterial anastomoses.[6] Because published descriptions vary, the inferior gemellus is best described as receiving arterial contributions from the inferior gluteal and medial circumflex femoral arterial systems rather than from one consistently agreed-upon single source.

References

  1. [1] Dalley AF II, Agur AMR. Moore’s Clinically Oriented Anatomy. 9th ed. Wolters Kluwer Health; 2022.
  2. [2] Lezak B, Massel DH. Anatomy, Bony Pelvis and Lower Limb, Gemelli Muscles. (Updated 2022 Aug 29). In: StatPearls (Internet). Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557420/
  3. [3] Dalley AF 2nd, Agur AMR. Moore’s clinically oriented anatomy. 9th ed. Philadelphia: Wolters Kluwer; 2023.
  4. [4] Lezak B, Massel DH. Anatomy, Bony Pelvis and Lower Limb, Gemelli Muscles. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2023.
  5. [5] Standring S, editor. Gray’s anatomy: the anatomical basis of clinical practice. 42nd ed. Amsterdam: Elsevier; 2021.
  6. [6] Gautier E, Ganz K, Krügel N, Gill T, Ganz R. Anatomy of the medial femoral circumflex artery and its surgical implications. J Bone Joint Surg Br. 2000;82(5):679-683.

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