The buttock artery that boards love to hang in front of you when the real answer is the femoral head. Learn the trap before it costs you a point.
The Set-Up
A 7-year-old boy has 8 weeks of insidious left thigh pain and a limp, with no trauma. He has restricted abduction and internal rotation, the leg is held in external rotation, and the hip swings into external rotation when you flex it. A pelvic radiograph shows widening of the left hip joint. This is idiopathic avascular necrosis of the femoral head. Which single artery is the dominant blood supply to that femoral head?
This is Legg-Calve-Perthes, idiopathic AVN of the femoral head. Once the child is past infancy, the dominant supply to the head is the medial circumflex femoral artery through its retinacular branches that wrap the posterior femoral neck. The inferior gluteal artery is the planted trap: it feeds the buttock and rides with the sciatic nerve, and it only chips in a minor collateral twig through the cruciate anastomosis. Wrong neighborhood. That is buttock and nerve, not the femoral neck.
scroll to dismantle the trap
Know your suspect
Meet the Inferior Gluteal Artery
Four facts make it unmistakable. Tap each tab. The whole point is that none of them is "femoral head."
Where it starts
Anterior Division, Internal Iliac
The inferior gluteal artery is a terminal branch of the anterior division of the internal iliac artery. It is one of the two big terminal branches of that anterior division (the other heading into the pelvis and perineum).
The chain
Internal iliac, then anterior division, then inferior gluteal. It is a pelvic vessel that leaves the pelvis. It never touches the femoral artery family.
Internal iliac splits front and back. The gluteal arteries are the two that escape the pelvis: superior gluteal off the posterior division, inferior gluteal off the anterior division.
The gluteal arteries escaping the pelvis: superior above the piriformis, inferior below it.Tap to enlarge
How it leaves
Below the Piriformis
It exits the pelvis through the greater sciatic foramen, passing below the piriformis (the infrapiriform foramenThe piriformis splits the greater sciatic foramen into a small gap above it (suprapiriform) and a larger gap below it (infrapiriform). Below equals inferior gluteal plus sciatic nerve.).
Direct contrast
The superior gluteal artery exits above the piriformis. The inferior gluteal exits below. Superior is up top, inferior is underneath. The muscle is the divider.
SuperIOR sits on top of the piriformis. InferIOR slides underneath. The piriformis is the shelf between the two floors.
The piriformis is the divider; the inferior gluteal artery slips out below it.Tap to enlarge
What it feeds
Buttock and Posterior Hip
Its main job is gluteus maximus and the overlying posterior hip and buttock. It also helps the short external rotators (obturator internus, gemelli, quadratus femoris) and the upper hamstrings.
Not on the list
The femoral head. The hip joint capsule head supply comes from the circumflex femoral arteries, not from this buttock vessel.
If the lesion is in the meat of the buttock or in gluteus maximus, think inferior gluteal. If the lesion is in the femoral head, walk away from it.
The medial circumflex femoral, not this buttock vessel, is what feeds the femoral head.Tap to enlarge
Who it travels with
The Sciatic Nerve Companion
It runs alongside the sciatic nerve as the artery to the sciatic nerveAlso called the arteria comitans nervi ischiadici, a persistent remnant of the embryonic axial artery of the limb. It is why a buttock vessel and a thigh nerve travel together.. It also joins the cruciate anastomosisA cross-shaped network behind the hip linking inferior gluteal, both circumflex femorals, and the first perforating branch of the deep femoral. It is collateral insurance, not the main pipe to the head. behind the hip.
The relationship to the answer
Through the cruciate anastomosis it makes only a minor collateral contribution toward the femoral region. It is never the dominant head supply. Collateral backup is not the same as primary supply.
Inferior gluteal rides shotgun with the sciatic nerve. Buttock plus nerve. The cruciate anastomosis is a side door, not the front door to the head.
Below the piriformis the inferior gluteal artery runs alongside the sciatic nerve.Tap to enlarge
The signature move
Above or Below the Piriformis?
One muscle decides which gluteal artery you are looking at. Tap a doorway and watch the vessel light up.
Five vessels, one answer
The Femoral-Head Lineup
When the stem says femoral head, these are the five names they offer. Flip each card for the one-line elimination.
A dying femoral head (Legg-Calve-Perthes): the structure this lineup is really fighting over.Tap to enlarge
The Trap
Inferior Gluteal
Buttock and gluteus maximus. Rides with the sciatic nerve. Minor cruciate collateral only.
tap to flip
Why it is wrong
It is a buttock vessel that exits below the piriformis with the sciatic nerve. Its only link to the femoral region is a small collateral twig in the cruciate anastomosis. That is backup, not main supply.
Wrong neighborhood. Buttock and nerve, not the femoral neck.
The Answer
Medial Circumflex Femoral
Wraps the posterior femoral neck. Its retinacular branches are the main head supply after infancy.
tap to flip
Why it wins
It curls around the back of the femoral neck and sends retinacular arteries up into the head. Damage it (posterior hip dislocation, displaced neck fracture) and the head dies. This is the dominant supply.
Posterior neck retinacular vessels feed the head. This is the answer.
Decoy
Superior Gluteal
Exits ABOVE the piriformis. Feeds gluteus medius, minimus, and tensor fasciae latae: the hip abductors.
tap to flip
Why it is wrong
Its territory is the abductors. Injure it (or its nerve) and you get a Trendelenburg gait, not femoral head death. It is on the wrong floor and the wrong job.
Above the piriformis, abductors. Wrong vessel, wrong floor.
Decoy
Deep Femoral
Profunda femoris. The parent trunk that gives off the medial and lateral circumflex femorals.
tap to flip
Why it is wrong
It is the parent, not the worker. It is too proximal and supplies thigh muscles. The head is fed by its branch, the medial circumflex femoral, so name the branch.
It is the parent, not the worker. Name the branch (MCFA).
Decoy
Artery of Ligamentum Teres
Tiny foveal artery from the obturator. Supplies a small area of the head in young children.
tap to flip
Why it is wrong
This foveal twig matters in toddlers, then largely regresses. In older children and adults it supplies a trivial sliver of the head. It is never the dominant supply the stem is after.
Tiny foveal twig. Matters in toddlers, trivial later.
Reason it out
Decide the Vessel
Guess before you tap. Each branch tells you why.
Step 1: A femoral head is dying from avascular necrosis in an older child. Which territory do you blame first?
The buttock (gluteal) vessels
The vessels wrapping the posterior femoral neck
Step 2: A different stem asks for the artery that exits ABOVE the piriformis. Which is it?
Superior gluteal artery
Inferior gluteal artery
Memory Hooks
Above vs Below
SuperIOR exits above, inferIOR exits below.🔑The piriformis is the shelf. Superior sits on top of it, inferior slides under it with the sciatic nerve.
The real answer
Medial circumflex femoral is the Main supply.🔑M for Medial, M for Main. It wraps the posterior femoral neck and the retinacular arteries climb into the head.
The trap
Inferior gluteal rides with the sciatic nerve.🔑Buttock plus nerve, not the neck. The cruciate anastomosis is a side door, not the front door to the head.
Five quick hits
Rapid Quiz
Five pulled from a larger pool. Reload for a new set. Tap an answer, read why.
Board-style practice
Clinical Walkthrough
Full vignettes. Answers shuffle each round. Right-click or long-press to cross out options. Double-tap to highlight.
Medically reviewed by Kaitlyn Cocuzzo, MD and Fatima Ali, DO · Last reviewed June 2026
Bone Wizardry is an independent educational resource for visual learning in the medical sciences. It is not affiliated with, endorsed by, or sponsored by any licensing or examination board, contains no real or recalled examination questions, and does not guarantee any educational or examination outcome.
