203 Gluteal And Thigh Muscles, Femoral Triangle , Arterial Supply Of The Thigh Flashcards
(43 cards)
Explain the Trendelenburg sign, importance, muscles invovled, causes , implication of positive sign
Trendelenburg Sign & Hip Abductor Function – Flashcard Questions
1. What is the purpose of the Trendelenburg test?
2. Which muscles are primarily responsible for hip abduction?
3. Which nerve innervates the gluteus medius and minimus muscles?
4. What is a positive Trendelenburg sign?
5. What causes the pelvis to drop on the unsupported side during the Trendelenburg test?
6. Why does weakness of the gluteus medius and minimus cause pelvic tilt?
7. How does the body compensate for a weak abductor during walking?
8. What is a compensated Trendelenburg gait?
9. Why does the trunk lean toward the affected side in compensated Trendelenburg gait?
10. What happens to the center of gravity when the trunk leans toward the affected side?
11. How does the Trendelenburg sign help identify superior gluteal nerve injury?
12. What spinal nerve roots contribute to the superior gluteal nerve?
13. During single-leg stance, how do hip abductors stabilize the pelvis?
14. What other conditions besides nerve injury can cause a Trendelenburg gait?
15. How would a patient with bilateral abductor weakness present when walking?
16. What is the difference between Trendelenburg gait and antalgic gait due to pain?
17. What anatomical side is being tested when a patient stands on their right leg?
18. In a positive Trendelenburg test, which side of the pelvis drops?
19. Why doesn’t the pelvis drop when hip abductors are functioning normally?
20. What is the function of the gluteus minimus compared to the gluteus medius?
Trendelenburg or waddling gait.
Trendelenburg sign is used to test the integrity of the hip abductor muscles. It occurs due to disruption of these muscles.
The two main muscles for hip abduction are gluteus minimus and medius. Medius is the main hip abductor. Both are innervated by superior gluteal nerve
Injury to L3-L5 nerve root or avulsion of the tendons of these muscles.
Abductor muscles keep the pelvis level during single stance or when patient stands on one leg. If you stand on both legs, each leg carries half the body weight.
When you’re standing on one leg, the supporting leg takes the entire load.
If the hip abductors connected to the supporting leg (leg touching the ground) are intact, the pelvis will remain level and the trunk will not lean towards any side.
ABDUCTOR
INJURY CAUSES TILT OF PELVIS
AWAY FROM AFFECTED
SIDE
If the abductor muscles of the supporting leg are injured or affected, then the patient will show the Trendelenburg sign.
When checking the integrity of the right side hip abductor muscles, stand behind the patient and ask the patient to stand on one leg. If the hip abductors connected to the supporting leg (leg touching the ground) are intact, the pelvis will remain level and the trunk will not lean towards any side.
Contra lateral hemi pelvis hip drop
Pelvis leans towards unaffected side but trunk leans towards affected side.
The trunk helps in stabilizing the pelvis and maintaining the center of gravity by leaning towards the affected side of the pelvis.
What happens when the gluteus medius/minimus muscles are weak?
• These muscles normally hold your pelvis level when you stand on one leg.
• When you lift one leg (like during walking), the muscles on the standing leg side contract to keep your pelvis from dropping on the side where the leg is lifted.
If those muscles are weak or not working:
• When you stand on that leg, the pelvis drops down on the opposite side (the side where the foot is lifted).
• This is because the weak muscles can’t hold the pelvis level.
What does this mean for walking?
• The person may develop a Trendelenburg gait, which looks like this:
• When they stand on the weak leg, they lean their upper body towards the weak side.
• This leaning helps reduce the force needed by the weak muscles to hold the pelvis steady.
• But it causes an abnormal walking pattern, and sometimes discomfort.
Why does the patient lean toward the weak side?
• Think of it like trying to balance a heavy load on one side.
• By leaning toward the weak side, they reduce the load or demand on the weak muscles, making it easier to stand or walk without falling.
Great question — and yes, it can seem counterintuitive at first. Let’s clear it up with anatomy, mechanics, and clinical reasoning behind the Trendelenburg sign:
📌 Why does the pelvis tilt down to the unaffected side in a positive Trendelenburg test?
Because the affected side’s muscles (gluteus medius & minimus) are too weak to hold the pelvis level when you’re standing on that leg.
🔍 Imagine this:
Let’s say the right gluteus medius and minimus are weak.
What happens during the Trendelenburg test:
1. The patient is asked to stand on the right leg (affected side).
2. The left leg (unaffected side) is lifted off the ground.
3. Normally, the right gluteus medius/minimus contract to keep the pelvis level.
4. But if they’re weak → they fail to stabilize the pelvis → so the pelvis tilts down on the left side (the unaffected, lifted side).
• Because there’s no muscular support to hold it up on the right side.
🟡 Result: Pelvis tilts downward on the unaffected (lifted) side — that’s the positive Trendelenburg sign.
🧍♂️ What about the lean?
When walking, patients will compensate:
• They lean toward the affected (weak) side during stance phase — this is called a compensated Trendelenburg gait.
• Why?
• Leaning toward the weak side moves the center of gravity closer to the hip joint.
• This reduces the torque and demand on the weakened muscles, helping prevent pelvic drop.
🔁 So, to clarify:
Situation What happens
Trendelenburg test Pelvis drops on the unaffected side when standing on the affected side
Gait (walking) Person leans toward affected side to compensate for weak hip abductors
Pain (e.g. arthritis) Patient may lean toward affected side due to pain, but this is a different mechanism from muscle weakness
Let me know if you’d like this illustrated or summarized in a diagram-style breakdown!
Here are the answers to the Trendelenburg and gluteal region flashcard questions for OSCE prep:
🦴 Trendelenburg Sign & Hip Abductor Function – Flashcard Answers
1. What is the purpose of the Trendelenburg test?
→ To assess the strength and integrity of the hip abductor muscles (mainly gluteus medius and minimus) on the weight-bearing leg.
2. Which muscles are primarily responsible for hip abduction?
→ Gluteus medius and gluteus minimus.
3. Which nerve innervates the gluteus medius and minimus muscles?
→ Superior gluteal nerve (L4, L5, S1).
4. What is a positive Trendelenburg sign?
→ Pelvis drops on the side of the lifted (unsupported) leg when the patient stands on the affected (supporting) leg.
5. What causes the pelvis to drop on the unsupported side during the Trendelenburg test?
→ Weakness or paralysis of the hip abductors on the supporting leg.
6. Why does weakness of the gluteus medius and minimus cause pelvic tilt?
→ These muscles normally contract to stabilize the pelvis. If they’re weak, they can’t counterbalance the weight of the opposite side.
7. How does the body compensate for a weak abductor during walking?
→ The patient leans their trunk toward the weak (affected) side to shift the center of gravity and reduce the demand on the abductors.
8. What is a compensated Trendelenburg gait?
→ A gait where the patient leans the torso toward the affected side to reduce pelvic drop caused by weak abductors.
9. Why does the trunk lean toward the affected side in compensated Trendelenburg gait?
→ To bring the center of gravity closer to the hip joint and reduce the load on the weak muscles.
10. What happens to the center of gravity when the trunk leans toward the affected side?
→ It moves closer to the hip joint, decreasing the lever arm and muscular effort needed.
11. How does the Trendelenburg sign help identify superior gluteal nerve injury?
→ Injury to this nerve weakens gluteus medius/minimus, leading to a positive Trendelenburg sign.
12. What spinal nerve roots contribute to the superior gluteal nerve?
→ L4, L5, and S1.
13. During single-leg stance, how do hip abductors stabilize the pelvis?
→ By contracting to prevent the pelvis from tilting downward on the unsupported side.
14. What other conditions besides nerve injury can cause a Trendelenburg gait?
→ Muscle tears, muscular dystrophy, hip joint dislocation, or avulsion of the gluteal tendons.
15. How would a patient with bilateral abductor weakness present when walking?
→ Waddling gait — alternating pelvic drops on each side, often seen in muscular dystrophy.
16. What is the difference between Trendelenburg gait and antalgic gait due to pain?
→ Trendelenburg gait is due to muscle weakness; antalgic gait is due to pain avoidance (limping).
17. What anatomical side is being tested when a patient stands on their right leg?
→ The right side — the supporting leg’s abductors are being tested.
18. In a positive Trendelenburg test, which side of the pelvis drops?
→ The side opposite to the one standing (the unsupported leg side).
19. Why doesn’t the pelvis drop when hip abductors are functioning normally?
→ The gluteus medius/minimus contract to hold the pelvis level during single-leg stance.
20. What is the function of the gluteus minimus compared to the gluteus medius?
→ Both abduct the thigh and stabilize the pelvis; gluteus minimus also assists in medial rotation.
Would you like this turned into a printable or digital flashcard deck?
The gluteal region is separated from the thigh by the gluteal fold and the left and right gluteal regions are separated from each other by a deep fissure called the gluteal cleft
The muscles of the gluteal region are grouped into two layers:
Superficial and deep layers
The ligament that spans from the ischial spine to the Ala of the sacrum
The ligament that spans from the ischial tuberosity to the Ala of the sacrum
These two ligaments create the greater and lesser sciatic foramen
SP ligament
ST ligament
Obturator membrane covers almost all the Obturator foramen leaving a small hole called the Obturator canal. The inguinal ligament which is the inferior thickening of aponeurosis of the external oblique abdominis muscle, will attach to ASIS stretching to the pubic tubercle, forming the base of the inguinal canal.
Below the inguinal ligament, there’s a gap. There’s a gap between the inguinal ligament and the superior aspect of the pubis and the anterior and inferior iliac spine. These gaps act as gateways to the greater ,lesser sciatic foramen, Obturator canal and the gap between inguinal ligament and pelvic bone is the soft inguinal space or sub inguinal space.
They acts as gateway for plenty structured to access the lower limb from the pelvis region
Sub inguinal space is divided into two by a fascia of the iliacus muscle. Part of the iliacus muscle fascia thickens and extends to the pecten pubis and blends with the inguinal ligament. That thickened part becomes the ileopectineal ligament. This ligament divides the subinguinal space into medial aperture and lateral aperture. Medial is a gateway for artery and veins. This medial aperture is also called lacuna vascularis cuz it only carries arteries and veins. The lateral aperture is a passageway for muscle and nerve. remember psoas major
comes from the posterior abdominal wall and the iliacus muscle so when the two muscles join, they pass under the inguinal
ligament via the lateral
aperture to go to the lesser trochanter so the lateral aperture is called lacuna muscularis
Femoral artery is the major arterial supply to the lower limb. This artery is actually the the external iliac artery
The external iliac artery becomes the femoral artery when it crosses the inguinal ligament.
The femoral vein as it ascends up and crossses the inguinal Ligament, the name changes to external iliac vein.
State The muscles in the superficial layer of the gluteal region(they are three)
Which is the most superficial?
Which muscle is the largest muscle in the body in terms of surface area?
Which muscle in the body is the largest in terms of density?
Gluteus max(most superficial and largest muscle in the body in terms of density but in terms of surface area, the largest muscle is the latissimus dorsi
Gluteus min
Gluteus medius
Tensor fascia lata is also considered to be part of the superficial gluteal layer.
What is the origins(4), insertions(2),action, innervation of the gluteus max
Origin: gluteal surface of the pelvic bone beyond the posterior gluteal line, also ST ligament, also Ala of the sacrum and also thoracolumbar fascia
Most fibers of the gluteus max comes from Elsewhere other than the posterior gluteal line
Insertion: these fibers converge inferiorly and the superior fibers insert at the ileotibial tract and the inferior fibers insert at the gluteal tuberosity on the dermis
Actions: its an anti gravity muscle cuz it can generate large amount of force to lift the body against gravity. Extensor of the thigh(main action), abduction, lateral rotation
Superior fibers are attached above the head of the femur so pulling it will cause head of femur will go medially while shaft goes laterally and that will cause abduction
Inferior fibers will bring femur close to midline so adduction
When you sit, you extend your thigh In order to get up. As you’re going up, you’re moving against gravity. So this gluteus max lifts you against gravity that’s why it’s dense. Also works when you’re climbing the staircase cuz you’re also going against gravity.
Men have bigger gluteus muscle
Innervation is inferior gluteal nerve
The tensor fascia lata
Origin
Insertion
Action
Innervation
It’s located on the lateral aspect of the thigh.
The tensor fasciae latae muscle is the most superficial muscle of the anterolateral aspect of the thigh. It is positioned lateral to the hip joint
Origin: gluteal surface anterior to the anterior gluteal line and along the lateral lip of the iliac crest or the part of the lateral
Lip that’s anterior to the anterior gluteal line is the origin
The tensor fascia lata muscle originates on the gluteal surface of the ilium, specifically between the anterior and inferior gluteal lines
Insertion: iliotibial tract
Action: it tightens or tenses the iliotibial band or tract and allows you stand firm
Assists in hip flexion, abduction, and medial rotation(from gpt)
Innervation: superior gluteal nerve (confirm. Dr Kyei said inferior)
It’s a key stabilizer for the hip and knee joints and plays a role in hip and knee movements like flexion, abduction, and internal rotation. The TFL connects to the iliotibial band (ITB), a thick band of connective tissue that runs along the outside of the leg.
Anatomy and Function:
Origin: The TFL originates from the anterior superior iliac spine (ASIS) and the anterior aspect of the iliac crest.
Insertion: It inserts into the iliotibial band (ITB).
Action: The TFL helps stabilize the hip and knee joints by tightening the iliotibial band. It also contributes to hip flexion, abduction, and internal rotation.
Nerve Innervation: The superior gluteal nerve (L4-S1) innervates the TFL.
Blood Supply: The TFL receives blood supply from the superior gluteal and lateral circumflex femoral arteries.
Clinical Significance: The TFL can become tight or cause pain due to overuse, weakness of surrounding muscles, or other factors.
In summary, the TFL is a muscle in the hip and thigh that stabilizes the hip and knee, contributes to various hip movements, and is connected to the iliotibial band.
Gluteus medius and minimus
Origin
Insertion
Action
Innervation
Origin: between posterior and anterior gluteal lines
Insertion: superolateral part of greater trochanter
Action: abduction, lateral rotation or external
Rotation or opening of thigh, stabilizes hip joint
Innervation: superior gluteal nerve
Minimus: gluteal surface between inferior and anterior gluteal lines
Insertion: greater trochanter
Same action as medius
Innervation: superior gluteal nerve
Supple: superior gluteal artery
Drainage: superior gluteal vein
So basically all the superficial gluteal muscles do abduction and lateral rotation
Medius has anterior and posterior fibers
Anterior cause medial rotation
Posterior cayse lateral rotation
Minimus always does medial rotation.
The action occurs at the joint and that explains how the muscle works.
Both mediums and minimus cause abduction cuz when the fibers pull, they pull medically but cause the insertion point where the joint is to move medically but the bone itself moves laterally
They stabilize the hip joint
Deep layer of the gluteal muscles are
Piriformis
Gamelus superior and inferior
Quadratus femoris
Obturator internus
Piriformis origin insertion action
Origin and insertion : anterior surface of the Ala of the sacrum and passes through greater sciatic foramen to get to the superior border of the greater trochanter that it inserts on when the foramen is divided into superior and inferior aperture
Action: abduction and lateral rotation
Innervated: nerve to piriformis which is a direct branch of the sacral
Plexus
Note that all the deep muscles insert at the greater trochanter except the quadratus femoris. These muscles are the primary lateral rotators of the hip
The structure that divides the greater sciatic foramen into superior and inferior apertures (or compartments) is?
Piriformis muscle
Gemellus superior and inferior
Origin
Insertion
Action
Innervation
Superior
Origin: ischial spine to
Insertion: medial surface of greater trochanter by the tendon of the Obturator internus
Action: abduction and lateral rotation
Innervation: nerve to Obturator internus
Obturator internus
Origin
Insertion
Its tendon Fits between gemellus inferior and superior
Origin:internal surface of Obturator membrane and adjacent bony structures
Insertion: medial surface of the greater trochanter
Action: abduction and lateral rotation
So Obturator internus, gemellus superior and inferior all insert at the medial surface of the greater trochanter but the G superior and inferior insert there via the tendon of the Obturator internus while lies between them
Innervation: nerve to Obturator internus
Because it loops around the ischial spine, it’s near the pudendal nerve — relevant in pudendal nerve blocks and pelvic surgeries.
Usually the origins of muscles are Medial and the insertion points of muscles are lateral
There’s a pivot where the joint is. The joint is the point of turning always. The superior portion to the joint always pulls medially while if the muscle is inferior to the joint, it always laterally
So when superior fibers are contracted, they pull head of femur medially and since there’s a pivot or joint there, the shaft will move laterally and thag will be abduction
The inferior fibers are contracted and pill the head medially and the shaft will follow medially cuz the Pivot is there so it’ll be pulled in the same direction as she shaft so the inferior fibers will cause adduction. But all the fibers being pulled medially will cause the shaft to laterally rotate and they will all extend. So extension is the main action and other actions will be abduction adduction and lateral rotation
But the medius and minimus, the medius has two fibers anterior and posterior fibers so posterior fibers do lateral rotation and anterior do medial rotation
But with minimus, it always does medial rotation.
If you still don’t understand the actions, watch a YouTube video. Period
You’re putting together an excellent conceptual understanding — this is how to truly learn anatomy: by visualizing the origins, insertions, axis of rotation, and how muscle fibers pull across a joint pivot. Let me help clarify, affirm, and refine your thoughts.
🔄 Muscles Work Like Levers Around Joints (Pivots)
You’re absolutely right:
• Muscles have origins (usually more medial/stable) and insertions (usually more lateral/moveable).
• When a muscle contracts, it pulls the insertion toward the origin, causing movement around a pivot (joint axis).
• Depending on where the fibers are located relative to the pivot, the same muscle can cause different actions.
🦴 Example: Gluteus Maximus
Fibers Origin (Medial) Insertion (Lateral) Primary Action
Superior fibers Iliac crest IT band (which inserts into lateral tibia) Abduction
Inferior fibers Sacrum & coccyx Gluteal tuberosity of femur Adduction
All fibers Medial origin → lateral insertion Pull posterior to hip joint axis Lateral rotation + Extension
✅ So yes — the direction of pull relative to the joint explains how the same muscle can perform multiple functions based on which fibers are activated.
🍑 Gluteus Medius & Minimus
Muscle Fiber Orientation Main Actions
Gluteus medius Anterior vs posterior Anterior → medial rotation Posterior → lateral rotation All → abduction
Gluteus minimus More uniform (anterolateral) Primarily medial rotation + abduction
So your understanding is ✅ correct:
• Medius has dual fiber roles: anterior = medial rotator, posterior = lateral rotator.
• Minimus acts mostly as a medial rotator (and abductor), and doesn’t contribute significantly to lateral rotation.
🔁 Extension, Rotation, Abduction/Adduction: How They Relate
For gluteus maximus:
• The fibers all pass posterior to the hip joint = powerful extensor.
• All fibers pull laterally, causing lateral rotation.
• Depending on which fibers fire:
• Superior = abduction
• Inferior = adduction
So yes — extension and lateral rotation are the main actions, while abduction/adduction depend on the fiber group.
✅ Final Summary (You’re Right!)
💡 When a muscle crosses a joint: • Its direction of pull across the joint pivot determines what movement it causes. • Gluteus maximus is a powerful extensor and lateral rotator. • Fiber direction explains why some parts abduct and others adduct. • Gluteus medius is more versatile: abduction + medial/lateral rotation. • Gluteus minimus is more uniform, mainly for abduction + medial rotation.
You’re thinking like a true clinician or anatomist. Let me know if you’d like a visual with fiber directions + joint axis!
Absolutely! Understanding muscles as levers working around joints (pivots) is foundational for mastering biomechanics and movement.
🧠 Big Idea: Muscles Act Like Levers
When a muscle contracts, it pulls on a bone — but how that pull translates into movement depends on how the muscle crosses the joint, and where its origin and insertion lie relative to the joint’s axis (pivot).
🛠️ Lever System in the Body: The Basics
In biomechanics, a lever has 3 parts:
Part In the Body Example
Lever arm The bone Femur, humerus, tibia, etc.
Fulcrum (pivot) The joint Hip joint, knee joint, etc.
Force Muscle contraction Gluteus maximus, biceps brachii, etc.
So a muscle contracts, pulls on a bone (lever), causing movement around the joint (pivot point/fulcrum).
🔄 Example: Gluteus Maximus & Hip Joint
• Origin: Medial — sacrum/ilium
• Insertion: Lateral — gluteal tuberosity or IT band
• Joint/Pivot: Hip joint
💥 When it contracts:
• It pulls the femur backward (extension) because the line of pull is behind the pivot.
• Since its fibers pull laterally → lateral rotation of the femur.
• Superior fibers are above the joint → cause abduction.
• Inferior fibers are below the joint → cause adduction.
🎢 How Direction of Pull Affects Motion
Let’s use a visual analogy: Think of the hip joint like a door hinge, and the femur like the door.
If you pull the top of the door sideways, it opens differently than if you pull the bottom.
• Superior pull (above joint) → Abduction
• Inferior pull (below joint) → Adduction
• Pull behind joint → Extension
• Pull in front → Flexion
• Pull across front → Medial rotation
• Pull across back → Lateral rotation
💡 Key Principle: Position Relative to Pivot = Function
Muscle Location Function
Crosses anterior to joint Flexion
Crosses posterior to joint Extension
Crosses lateral to joint Abduction
Crosses medial to joint Adduction
Fibers pull anteriorly & transversely Medial rotation
Fibers pull posteriorly & transversely Lateral rotation
🧠 Bonus Example: Biceps at the Elbow
• Fulcrum: Elbow joint
• Force: Biceps pulling on radius
• Load: Forearm/hand
When the biceps contracts, it pulls the forearm up → elbow flexion.
But if the insertion were behind the joint? It would cause extension.
🔁 Summary
• Joints = Pivots or hinges
• Bones = Levers
• Muscles = Forces that pull
• The position of the muscle relative to the pivot determines the direction of movement
• Muscles can have multiple actions if they have different fiber angles (like gluteus medius)
Would you like a table of specific muscles and how they act as levers, or an animation/gif to see this in motion?
Brilliant question! You’re thinking deeply about position, direction of pull, and movement around the joint — and this is how you master anatomy!
Let’s walk through this clearly and simply, like a mini detective story 🕵️:
🧩 First, Let’s Revisit the Rule You Mentioned:
You said:
“The superior portion to the joint always pulls medially, while the inferior portion pulls laterally.”
That sounds like it could be true in some cases — but it’s not a universal rule.
In fact, the direction a muscle pulls depends on:
• Where it starts (origin),
• Where it ends (insertion), and
• How its line of pull relates to the joint’s pivot.
So let’s look at gluteus medius and minimus — and see why they abduct, not adduct.
🎯 What Is Abduction?
Abduction means lifting your leg away from the midline — like when doing a jumping jack.
Imagine your hip as a hinge, and your leg as a stick.
If you tie a rope on top of the stick, and pull straight up, the stick lifts outward = abduction.
🦴 Now Look at Gluteus Medius & Minimus
Feature Gluteus Medius / Minimus
Location On the side of the pelvis, above the hip joint
Direction of pull From the pelvis (origin) to the greater trochanter (insertion)
Relative to hip Their line of pull is lateral to the joint
Action Abduction (pulls the femur out to the side)
✅ They are not pulling the femur medially.
Instead, they pull laterally and upward, which causes abduction.
🤔 Why Not Adduction?
If they pulled the femur toward the midline, that would be adduction.
But they don’t — their pull is from superolateral to inferolateral, so when they contract, they pull the greater trochanter up and out → abduction.
💡 Helpful Visualization
• Imagine you’re standing straight.
• A muscle on the outer side of your hip pulls the top of your thigh upward and outward.
• That’s what gluteus medius and minimus do → they pull the femur out to the side.
🔄 Medial vs. Lateral Rotation
Now, they do pull the head of the femur medially — and that causes medial rotation, especially the anterior fibers.
So you’re partially right!
🧠 The head of the femur rotates medially, but the shaft of the femur moves laterally = abduction + medial rotation.
✅ Final Summary:
• Gluteus medius and minimus are above and lateral to the hip joint.
• They pull the femur outward and slightly forward, not inward.
• That causes abduction (main action) and medial rotation (especially for anterior fibers).
• Your idea of pulling medially if above the joint is true for rotation, but not for abduction/adduction — those depend on whether the muscle is medial or lateral to the joint.
Want a simple sketch to show this in action?
You’re doing great by asking questions — this is a tricky topic, but I’ll explain it even more simply, like a picture in words. Let’s imagine it together. 🧠🎨
🌟 Imagine This First:
🎯 You are a robot with a long stick for a leg, and your hip is the hinge (the joint).
Your muscles are like ropes pulling on that stick.
Where the rope is attached (left or right, front or back) tells you what direction the stick will move when the rope pulls.
💡 What Is the “Line of Pull”?
The line of pull is just the direction the muscle pulls from, based on:
• Where it starts (origin), and
• Where it ends (insertion),
• And where the joint is in between.
The direction of the pull compared to the middle of the joint tells you if it’s:
• ➡️ Lateral (pulls from outside → away from the middle)
• ⬅️ Medial (pulls from inside → toward the middle)
🏃 Think of Your Leg
Let’s say you’re standing up straight.
• Your hip joint is the hinge.
• The middle of your body is the midline (imagine a vertical line through your belly button).
• Now imagine a muscle on the inside of your thigh — like adductor longus.
👉 When it pulls, it pulls toward the middle of your body = medial pull → adduction.
Now imagine a muscle on the outside of your hip — like gluteus medius.
👉 When it pulls, it pulls outward, away from the midline = lateral pull → abduction.
🎮 Muscle Actions = Based on Pull Direction Around the Joint
Where Muscle Is Located Direction of Pull Resulting Movement
Medial to joint Pulls inward Adduction
Lateral to joint Pulls outward Abduction
In front of joint Pulls forward Flexion
Behind the joint Pulls backward Extension
📌 Simple Example:
Let’s look at adductor longus:
• Starts on the pubis (inside of the hip)
• Ends on the inner femur
• The rope (muscle) pulls inward, so your leg moves toward the other leg → medial pull = adduction
Now gluteus medius:
• Starts on the outside of the pelvis
• Ends on the outside of the thigh
• Pulls your leg away from the body → lateral pull = abduction
🌈 Final Visual
Imagine the hip joint like a door hinge:
• If the rope is pulling from the inside of the door, it swings inward → medial
• If the rope is pulling from the outside, the door swings outward → lateral
Would you like me to draw this as a super simple diagram to show exactly how the ropes/muscles pull from medial or lateral?
Quadratus femoris origin insertion action
one of the deep gluteal muscles — short, square, and powerful! 💪
🟪 Quadratus Femoris — The Basics
Feature Description
Shape Flat and square-shaped (“quadratus” means square)
Location Deep in the buttock, under the gluteus maximus
Function Lateral rotation and stabilization of the hip joint
📍 Origin & Insertion
• Origin: Lateral border of the ischial tuberosity (the sitting bone)
• Insertion: Intertrochanteric crest (specifically the quadrate tubercle) on the posterior femur
👉 Line of Pull:
It pulls horizontally, from medial (ischium) to lateral (femur).
⚙️ Actions
Action Explanation
✅ Lateral rotation of the thigh Rotates the femur outward (especially when standing or walking)
✅ Stabilizes the hip joint Helps keep the femoral head securely in the acetabulum
🧠 It’s like a belt pulling the back of the thigh outward to rotate your leg laterally.
🔌 Nerve Supply
• Nerve to quadratus femoris
• From L4, L5, S1 (a branch of the sacral plexus)
(Note: This nerve also innervates inferior gemellus.)
🩻 Clinical Relevance
• Injury or tightness in quadratus femoris can compress the sciatic nerve (just above it), leading to deep buttock pain (like deep gluteal syndrome).
• Weakness affects lateral rotation and hip stability, especially when walking or changing direction.
📌 Easy Way to Remember:
“Quadratus femoris is the square muscle that pulls your thigh out and holds your hip tight.”
Would you like a labeled diagram to help visualize it?
Great question! Let’s clear this up simply:
🟪 Quadratus Femoris
Main action: ✅ Lateral rotation of the thigh at the hip
Extra action: ➖ Weak adduction (when the hip is flexed)
🧠 Why?
• Quadratus femoris runs horizontally from the ischial tuberosity to the intertrochanteric crest.
• This line of pull is medial to lateral, below the axis of the hip joint.
• That horizontal pull rotates the femur outward → lateral rotation.
When the hip is flexed, the muscle’s line of pull also brings the thigh closer to the body’s midline → a little adduction.
🧾 Summary:
Action Strong or Weak?
✅ Lateral rotation Strong
➖ Adduction (hip flexed) Weak
❌ Abduction No
So no — quadratus femoris does not do abduction. It does lateral rotation and a little adduction when your hip is bent.
The nerve to quadratus femoris passes through the greater sciatic foramen and under the piriformis muscle as it enters the gluteal region.
So in order of movement from the first muscle you see in deep layer, we have from piriformis, we go to gemellus superior then we get to Obturator internus tendon then we get to gemellus inferior and finally quadratus femoris
What’s the diff between the tensor fascia lata and the fascia lata?
Excellent question! It’s very common to mix up Tensor Fasciae Latae (TFL) with the Fascia Lata, but they’re actually quite different things. Let’s break it down clearly and simply:
🟦 1. Tensor Fasciae Latae (TFL) — This is a Muscle
Feature Description
Type Skeletal muscle
Location Upper outer thigh, just in front of the hip
Origin Anterior part of the iliac crest and ASIS (anterior superior iliac spine)
Insertion Iliotibial tract (IT band)
Action - Helps with hip flexion, abduction, medial rotation
- Stabilizes the **knee joint** via the IT band |
✅ It’s an actual muscle that contracts, and it “tenses” the fascia lata — that’s where it gets its name: Tensor (tightener) of the fascia lata.
🧵 2. Fascia Lata — This is a Sheet of Connective Tissue
Feature Description
Type Deep fascia (not a muscle)
Location Surrounds all thigh muscles like a sleeve
Function - Holds muscles in place
- Helps venous return by compressing veins
- Transfers force via the **iliotibial tract** (lateral part) |
| Specialization | Thickens laterally to form the Iliotibial (IT) band |
❌ It doesn’t contract. It’s like a tight stretchy bodysuit that surrounds and supports the muscles.
🤝 Their Relationship
• The TFL muscle inserts into the fascia lata (specifically the IT band part of it).
• When the TFL contracts, it tightens (tenses) the fascia lata, especially the IT band — helping stabilize the knee during walking or running.
📌 Summary Table
Feature Tensor Fasciae Latae (TFL) Fascia Lata
Type Muscle Deep fascia (connective tissue)
Location Anterolateral hip Surrounds thigh muscles
Function Moves hip & stabilizes knee Supports muscles, distributes force
Contracts? Yes No
Connected to Fascia lata (via IT band) Receives tension from TFL & glute max
Let me know if you’d like a diagram to show the difference between the two!
✅ Yes, the Tensor Fasciae Latae (TFL) absolutely tenses the Iliotibial (IT) tract.
That’s actually one of its main jobs — and it’s even in its name:
Tensor = to tense or tighten Fasciae Latae = refers to the fascia lata, of which the IT tract is a thickened part on the lateral thigh
🧠 How it works:
1. The TFL originates from the iliac crest/ASIS.
2. It inserts into the IT tract, which is a thick band of fascia running down the lateral thigh.
3. When the TFL contracts, it pulls on the IT tract, tightening it.
🎯 Why this matters:
• A tight IT tract helps to stabilize the knee, especially during activities like walking, running, or standing on one leg.
• TFL works with gluteus maximus (which also inserts into the IT tract) to:
• Stabilize the pelvis
• Support the lateral knee joint
📌 Summary:
Muscle Inserts into IT Tract? Tenses IT Tract? Function via IT Tract
Tensor Fasciae Latae ✅ Yes ✅ Yes Hip flexion, abduction, knee stability
Gluteus Maximus ✅ Yes (upper fibers) ✅ Yes Hip extension, knee stability
Let me know if you’d like a simple visual to show this connection!
Innervation | Superior gluteal nerve (L4, L5, S1) |
Fascia lata is a deep Dacia that covers entire thigh and blends with gluteal aponeurosis and when it crosses the inguinal region of the groin, it fuses with the superficial fascia of the abdomen which is divided into two an outer fatty tissue layer(camper’s fascia) and inner membrane of thin fibrous sheet( scarpa’s fascia) and these fuse inferiorly and blend with the fascia lata
Inferior Fusion & Blending:
➤ As you go inferiorly (toward the thigh):
• Camper’s fascia continues into the thigh, becoming part of the fatty layer of the superficial fascia of the thigh.
• Scarpa’s fascia becomes thinner and denser, and it:
✅ Fuses with the fascia lata (deep fascia of the thigh) about 2 cm below the inguinal ligament.
📌 Why this matters:
• This fusion forms a barrier that prevents fluid (like urine or blood) from spreading from the abdomen into the thigh — which is clinically important in injuries like urethral rupture.
• Instead, such fluids can spread upward into the abdominal wall or into the scrotum/labia, but not into the thigh.
🧠 Easy Summary:
The superficial fascia of the lower abdomen has a fatty outer layer (Camper’s) and a fibrous inner layer (Scarpa’s). Scarpa’s fascia fuses with the fascia lata, forming a barrier between the abdomen and thigh. If you want to see any muscle in the thigh, you have to cut the fascia lata.
The position of the sciatic nerve should be considered when giving IM injection at the gluteal region. You must decide the region into four quadrants (superior lateral, superior medial, inferior lateral and inferior medial)
Superior lateral is the safest point for injection. Anywhere else you’re likely to come into contact with the sciatic nerve and cause paralysis
✅ You’re absolutely right — the superolateral quadrant of the gluteal region is the safest site for intramuscular (IM) injections, and here’s why:
💉 Why the Superolateral Quadrant?
The gluteal region is divided into four quadrants by drawing:
• A vertical line from the iliac crest to the gluteal fold, and
• A horizontal line from the midpoint of the gluteal region.
This creates:
Quadrant Risk
Superolateral ✅ Safest!
Superomedial ❌ Risk of hitting superior gluteal vessels/nerves
Inferolateral ❌ Close to sciatic nerve
Inferomedial ❌ Highest risk — sciatic nerve + major vessels
📍 The sciatic nerve travels through the inferomedial quadrant.
• Injecting there risks nerve injury, which can cause:
• Paralysis
• Severe pain
• Numbness or weakness in the lower limb
✅ Safest IM Injection Site
Target the upper outer quadrant (superolateral), specifically the gluteus medius muscle — away from the sciatic nerve.
🧠 Clinical Tip (Alternative Method):
Use the “V method”:
1. Place your palm over the greater trochanter.
2. Point your index finger toward the anterior superior iliac spine (ASIS).
3. Spread your middle finger back along the iliac crest.
4. Inject between the two fingers — in the gluteus medius, safe from major nerves.
Let me know if you’d like a labeled diagram showing safe and unsafe areas!
The thigh is between the gluteal region and the leg.
The thigh helps you lift your body when sitting down and you want to jump.
The muscles and Neuro vascular structures are bound by a tough deep fascia called fascia lata. So outer skin then you get to the fatty layer before you get to the fascia lata. If you have uneven distribution of fat in the thigh, the skin on the thigh won’t be smooth.
Fascia lata will send septa or divisions to the femur demarcating the arrangement of the muscles in the thigh . This organizes the muscles into anterior, medial and posterior compartments
Each compartment is unique cuz it has its own nerve supply
Anterior compartment of the thigh helps you flex thigh at hip joint and gluteal part helps you extend the thigh and some muscles in posterior compartment support the gluteal muscles for extension
Muscles in the anterior compartment are innervated by femoral nerve
Muscles in posterior compartment do extension of thigh,flexion of knee and medial and lateral rotation of the knee joint
Posterior compartment are innervated by sciatic nerve. Medial compartment muscles are for adduction of thigh (gluteal muscles did abduction of the thigh).
It is easier to abduct the thigh than to adduct it.
Medial compartment muscles are innervated by Obturator nerve
Compartment,Action,Main Nerve,Key Muscles
Anterior, Flex hip, extend knee,Femoral,Quads, iliopsoas, sartorius
Posterior,Extend hip, flex knee,Sciatic,Hamstrings
Medial,Adduct thigh,Obturator,Adductors, gracilis, obt. externus
State the muscles in the Anterior compartment of the thigh
Muscles are:
Psoas major
Iliacus
Sartorius
Pectineus(can be considered both anterior and posterior )
Quadriceps femoris (Vastus medialis ,Vastus intermedia
Vastus lateralis
Rectus femoris)
Sure! Here’s an easy mnemonic to help you remember the main muscles of the anterior compartment of the thigh:
🎓 Mnemonic: “I Quit Studying Physiology”
Each letter stands for one muscle:
• I – Iliopsoas (Iliacus + Psoas major)
• Q – Quadriceps femoris
• (Rectus femoris, Vastus medialis, Vastus lateralis, Vastus intermedius)
• S – Sartorius
• P – Pectineus (shared with medial compartment but mainly femoral nerve)
✅ Bonus Facts:
• Iliopsoas: Strong hip flexor
• Quadriceps femoris: Main knee extensor
• Sartorius: Flexes hip and knee, helps in crossing legs
• Pectineus: Adducts and flexes thigh (sometimes innervated by both femoral and obturator nerves)
📌 Summary:
“I Quit Studying Physiology” → Iliopsoas, Quadriceps, Sartorius, Pectineus
Would you like a visual diagram to go with it?
State the origin insertion innervation action of psoas major
Psoas major: origin- transverse process of L1-L4 vertebra and bodies of L1 to L4 and its associated intervertebral discs.
Insertion: The muscle belly of psoas major descends through the posterior abdominal wall, enters the pelvis, and passes under the inguinal ligament through the muscular lacuna or lacuna muscularis (not vascular lacuna). It joins the tendon of iliacus, and together they insert onto the lesser trochanter of the femur as the iliopsoas tendon.
Innervation: Anterior rami of L1-L3 spinal nerve(these are just coming out and haven’t joined the plexus yet)
State the origin insertion innervation action of iliacus
Iliacus
Origin : iliac fossa
Insertion: muscle belly also passes lacuna muscularis, go under the inguinal ligament and joins the psoas major tendon to insert at lesser trochanter
Innervation: nerve to iliacus which is a branch of femoral nerve
Both muscles(iliacus and psoas major ) flex the thigh. They’re not Powerful flexors. If person is in supine position such that your ventral side is up , and wants to sit so you have to lift your trunk and in this case, your thighs are stationary , the psoas and iliacus muscle lifts the trunk up
If you’re flexing the trunk, thigh is stationary
If you’re flexing the thigh, the trunk is stationary
State the origin insertion innervation action of sartorius
Sartorius muscle is also called what muscle?
Root of femoral nerve is L2,L3 and L4.
You had the problem with the action so watch a video on it
So for the anterior muscles, you start with sartorius from medial to lateral and then you go to Vastus medialis and then rectus femoris and Vastus intermedia under it and then most lateral is Vastus lateralis and that’s it for the anterior compartment
Sartorius muscle: longest muscle in the body. Also called tailors muscle.
Origin: anterior superior iliac spine
Insertion: crosses obliquely to the anteromedial surface of medial condyle of the tibia via pes anserinus
Belt muscle.
Innervation: femoral nerve
Flexion of the thigh at the hip joint while the leg is stationary
Medial rotation of the foot
Extension of the leg at the knee joint
Lateral rotation of the thigh but medial rotation of the leg
What is pes anserinus
🦵 Pes Anserinus (Goose’s Foot)
Pes anserinus is the conjoined insertion of three muscles from different compartments of the thigh that attach to the anteromedial surface of the proximal tibia. It’s named “goose’s foot” because the tendons spread out like a goose’s webbed foot.
🧠 Mnemonic to Remember the Muscles:
“Say Grace before Tea”
Muscle Compartment Nerve
S – Sartorius Anterior Femoral nerve
G – Gracilis Medial Obturator nerve
T – Semitendinosus Posterior Tibial nerve (from sciatic)
📍 Location:
• Found medially below the knee, on the superomedial surface of the tibia.
• Lies just deep to the skin and superficial to the medial collateral ligament (MCL).
🩺 Clinical Relevance:
• Pes anserine bursitis: Inflammation of the bursa beneath the pes anserinus — common in runners or overweight individuals with osteoarthritis.
Would you like a labeled diagram or a clinical case example for pes anserinus?
