Gemellus Inferior

Origin, Insertion, Action, Innervation

Origin: Upper border of the ischial tuberosity
Insertion: Medial surface of the greater trochanter of the femur, via the obturator internus tendon (blends with the lower border of the tendon)
Action:
Primary: External (lateral) rotation of the hip
Stabilization of the femoral head in the acetabulum
Abduction of the hip when the hip is flexed
Innervation: Nerve to quadratus femoris from the sacral plexus (L4, L5, S1) — shares innervation with quadratus femoris, not obturator internus

Palpation Guide

Client position: Sidelying, affected side up, hip flexed approximately 45 degrees, pillow between the knees.
Landmark sequence:

Locate the greater trochanter and the ischial tuberosity.
Find the obturator internus–gemelli complex zone: the space between the piriformis line (above) and quadratus femoris (below), approximately halfway between the ischial tuberosity and the greater trochanter.
Gemellus inferior lies at the inferior edge of this complex, immediately superior to quadratus femoris.
In practice, it cannot be distinguished from the obturator internus tendon or gemellus superior by palpation alone. Treat the complex as a unit.

Tissue feel: Indistinguishable from the obturator internus–gemelli complex. Part of the continuous band of deep rotator tissue.
Confirmation test: Resisted external rotation activates the entire deep six group. No clinical test isolates gemellus inferior.
Common errors:
Attempting individual muscle isolation — the gemelli are too small and too intimately blended with the obturator internus tendon for individual palpation.

Trigger Point Referral

Common TrP locations: Within the obturator internus–gemelli complex, near the ischial tuberosity origin. TrPs are attributed to the complex rather than to individual muscles.
Referral pattern: Deep aching in the posterior buttock between the ischial tuberosity and greater trochanter.
Clinical significance: Gemellus inferior originates from the ischial tuberosity — the same landmark as the hamstring origin. TrP pain at this location can be confused with proximal hamstring tendinopathy (also called "high hamstring" pain). If a client points to the ischial tuberosity and says it hurts with sitting but hamstring-specific testing is negative, the deep rotators (including gemellus inferior) may be the source.

Trigger point referral diagram — coming soon

Image coming soon. For visual reference, see [Gemellus Inferior at TriggerPoints.net](http://www.triggerpoints.net/muscle/gemellus-inferior).

Clinical Notes

Common conditions:

Part of the deep rotator complex relevant to conditions/piriformis-syndrome differential.
Relevant to proximal hamstring tendinopathy differential — gemellus inferior shares its origin (ischial tuberosity) with the hamstrings, making symptom location overlap common.
Relevant to conditions/hip-osteoarthritis — guards alongside the other deep rotators in response to joint degeneration.

What you'll typically find:

Never symptomatic in isolation. Presents as part of the deep rotator complex.
Because gemellus inferior shares innervation with quadratus femoris (nerve to quadratus femoris, L4–S1), these two muscles are neurologically linked — they activate together, separate from the gemellus superior–obturator internus pair.
Ischial tuberosity tenderness that does not correlate with hamstring loading (negative resisted knee flexion, negative hamstring stretch tests) should prompt consideration of the deep rotators.

Treatment effects:

Treated as part of the deep rotator strip from piriformis to quadratus femoris. Longitudinal stripping from the piriformis line to the ischial tuberosity covers the entire complex.
When working near the ischial tuberosity, sustained compression affects both gemellus inferior and the proximal hamstring attachments. Differentiate by having the client alternately contract external rotation (deep rotators) and knee flexion (hamstrings) to determine which structure is producing the tenderness.

Cautions:

The sciatic nerve passes through this region. Monitor for radiating leg symptoms during treatment.
The ischial tuberosity region is close to sensitive anatomy — communicate clearly about hand placement and maintain professional boundaries.

Clinical pearl:

Note the split innervation of the gemelli: gemellus superior is innervated by the nerve to obturator internus (L5, S1, S2), while gemellus inferior is innervated by the nerve to quadratus femoris (L4, L5, S1). This means upper and lower deep six muscles can be affected differently in lumbar nerve root lesions — an L4 radiculopathy would more likely affect gemellus inferior and quadratus femoris, while L5/S1 would affect piriformis, gemellus superior, and obturator internus.

Assessment

Resisted external rotation (shared with all deep six):

Client supine with hip and knee flexed to 90 degrees. Resist external rotation at the ankle. Tests the group collectively.

Passive hip internal rotation:

Client prone with knee flexed to 90 degrees. Let the foot fall laterally. Less than 30 degrees of internal rotation suggests deep rotator tightness.

Muscle Groups

Deep six hip external rotators (anatomical):

Obturator internus–gemelli complex (functional unit):

Related Muscles

Functional unit:

anatomy/muscles/obturator-internus — the central muscle of the complex
anatomy/muscles/gemellus-superior — brackets the superior border of the obturator internus tendon

Shared innervation:

anatomy/muscles/quadratus-femoris — shares nerve to quadratus femoris (L4, L5, S1)

Adjacent deep six:

anatomy/muscles/quadratus-femoris — lies immediately inferior
anatomy/muscles/piriformis — most superior of the deep six

Antagonists (hip internal rotation):

anatomy/muscles/gluteus-medius (anterior fibers)
anatomy/muscles/gluteus-minimus
anatomy/muscles/tensor-fasciae-latae

Key Takeaways

Part of the obturator internus–gemelli complex — treated as a group, never isolated clinically.
Shares its ischial tuberosity origin with the hamstrings — ischial pain with negative hamstring tests suggests deep rotator involvement.
Innervated by the nerve to quadratus femoris (L4–S1), distinct from gemellus superior — the gemelli have split innervation.