Muscles of the Gluteal Region

Posterior View and Lateral View of the Gluteus Muscles

• All the gluteus muscles take their origin from the dorsal aspect of the hip bone, and  insert into the femur bone.
• There are three types of Gluteal muscles:
  • Gluteus Maximus- It is the largest muscle among the three muscles. The other  muscles cannot be found until you remove the gluteus maximus. It takes its origin from the dorsum of the hip bone as well as from the dorsum of the sacrum and also has ligaments. Insertion is on the gluteal tuberosity on the posterior aspect of the upper femur bone. Three important actions of the gluteus maximus-
    • It is the chief muscle for hip extension by pulling the femur bone posteriorly.
    • It is inserted in such a way that it rotates the femur bone laterally at the hip joint.
    • Upper fibers of the Gluteus maximus will pull the femur in such a way that the femur moves away from the body, which is called abduction. The fibers are inserted behind the axial line. The Nerve supply of gluteus maximus muscle is by the  inferior gluteal nerve
  • Gluteus Medius- It originates from the dorsum of the hip bone. It is inserted into the lateral surface of the greater trochanter bone of the femur. This muscle will pull the femur away from the body. Hence it works as an abductor muscle
  • Gluteus Minimus- It is the anterior most muscle among the three. It originates from the dorsum of the hip bone. It is inserted into the anterior surface of the greater trochanter of the bone. Gluteus mediums, gluteus minimus and tensor fasciae latae are the trio muscles that are supplied by the single nerve (superior gluteal nerve). This muscle will pull the femur away from the body. Hence it also works as an abductor muscle.

Trio Muscles Action

The trio muscle action involves Gluteus Medius, Gluteus Minimus, and Tensor Fasciae Latae. They are mainly used for pulling the femur bone away from the body. So, they are the abductor muscles.

The insertion of the fibers is anterior to the axial line. These muscles rotate the femur medially at the hip joint. If we are using TRIO muscles along with the Gluteus maximus, they help in the hip abduction. But the medial rotation is canceled by the lateral rotation. Because gluteus maximus is larger as compared to the other two

Another action of the Trio muscles is that they help in the pelvic stabilization

Piriformis Muscle

The Hip bone is present anteriorly, and it has the ileum superiorly, the pubis anteriorly and the Ischium part (Ischial tuberosity) posteriorly. The above three parts will meet at a point which forms the acetabulum. The head of the femur goes to the acetabulum and makes the hip joint. The greater trochanter nerve is also present on the femur bone.

The piriformis muscle inserts superiorly into the tip of the greater trochanter. The origin of piriformis muscle is from the anterior surface of the sacrum bone in the pelvis region. Then it comes out from the greater sciatic foramen to enter the gluteal region and insert on the tip of the greater trochanter bone of the femur. The Ischial spine is located medially between the superior greater sciatic notch and inferior lesser sciatic notch. These notches are converted into foramen by some ligaments. Sacrospinous ligament coming from sacrum bone to the ischial spine.This ligament helps to convert the notches into the foramen. Sacrotuberous ligament is coming from sacrum to ischial tuberosity (superficial ligament). This ligament helps to convert the lesser sciatic notch into lesser sciatic foramen

Pyriformis passes through the greater sciatic foramen where it comes from the pelvis region into the gluteal region. It is key muscle for the passage of the structures as some structures passes above  it and Some structures passes below it.

One nerve passes superior to piriformis called superior gluteal nerve and one nerve passes inferior to piriformis called inferior gluteal nerve. Inferior gluteal nerve supplies the gluteus maximus. Superior gluteal nerve supplies the TRIO muscles.

Some other structures passing through greater sciatic foramen below piriformis include The Sciatic Nerve. Sciatic, superior gluteal, and inferior gluteal nerves originate from the lumbosacral plexus in the pelvis and then reach the gluteal region through the greater sciatic foramen. After that, sciatic nerve runs in the posterior thigh region.

The PIN structures pass through the greater sciatic foramen and enter into the lesser sciatic foramen. They include:

• P: Pudendal nerve
• I: Internal pudendal vessels
• N: Nerve to obturator internus

These structures originate from the pelvis region and hook behind the ischial spine in the gluteal region behind the sacrospinous ligament. They enter into the lesser sciatic foramen and move to the perineum for supplying the muscles & skin in the perineal region.

Also Read: Development of Genito-Urinary System

PIN Structures

The Gluteus maximus has two insertions. 25% of the fibers are inserted on to the posterior aspect of the upper femur at the gluteal tuberosity and the remaining 75% of the fibers are inserted into the tibia anteriorly (Gerdy's tubercle) and continues into the iliotibial tract. Iliotibial tract is the modification of deep fascia & collagen fibers on the lateral aspect of the thigh and continues down to the tibia. It is called iliotibial tract because it comes from the ilium bone and goes towards the tibia. It is the region for the insertion of the two muscles, namely, Gluteus maximus (large muscle) posteriorly and Tensor fasciae latae (small muscle) anteriorly.

Tensor fascia latae originates from the hip bone and inserts into the iliotibial tract. The Gluteus medius, gluteus minimus and tensor fasciae latae are together called the Trio muscles that are supplied by the single nerve (superior gluteal nerve). Gluteus maximus is cut to see the gluteus Medius, which is present deep to the maximus anteriorly.

If gluteus Medius is cut, gluteus minimus is found deeper anteriorly to the Medius. The superior gluteal nerve comes from the lumbosacral plexus in the pelvis region and passes through the greater sciatic foramen above the piriformis muscle and supplies the TRIO muscle.

Inferior gluteal nerve passes the greater sciatic foramen below the piriformis to enter the gluteal region and supplies the gluteus maximus. These are called inferior and superior muscles in relation to the piriformis muscle, and they insert on to the tip of the greater trochanter of the femur bone. Posterior cutaneous nerve passes to the sciatic nerve to the posterior thigh and supplies the skin of the posterior thigh.

As read earlier the PIN structures include Pudendal nerve, Internal pudendal vessels and Nerve to obturator internus. These structures come from the greater sciatic foramen and hook behind the ischial spine in the gluteal region and go to the lesser sciatic foramen and continue towards the perineum region. Nerve to obturator internus covers the obturator foramen from the inner side. The tendon of Obturator Internus muscle will insert into the femur bone. This tendon is sent between the two muscles, namely, Superior gemellus muscle and Inferior gemellus muscle. 

If you remove the glutes muscle, then you will find the different muscles like Piriformis muscle, Superior gemellus muscle, Inferior gemellus muscle, Obturator internus, and Quadratus femoris muscle which is a quadrangular muscle attaching to the femur bone. These all muscles are short lateral rotators at the hip joint and turn the femur bone laterally.

TRIO muscles will not perform lateral rotation rather a medial rotation is present. 

Dissected Specimen of Gluteal Muscle

Gluteus maximus takes its origin from the dorsum of the hip bone as well as from the dorsal of the sacrum and have the ligaments. The Insertion includes:

• 25% of the fibers are inserted on to the posterior aspect of the upper femur at the gluteal tuberosity
• 75% of the fibers are directed into the iliotibial tract.

The Iliotibial tract also receives the insertion from the tensor fascia latae (anterior). This iliotibial tract further continues into Gredy’s tubercle on the anterior aspect of the tibia. Piriformis muscle comes from the greater sciatic foramen and inserts into the tip of the greater trochanter. The piriformis muscle will decide about the structures inferior or superior and inferior to it. Superior gluteal nerve passes through the greater sciatic foramen superior to piriformis and supplies the TIRO muscles. Inferior gluteal nerve passes under the piriform and supplies the gluteus maximus (largest muscle). The sciatic nerve will supply the posterior thigh and the posterior cutaneous nerve is also supplied to posterior thigh.

PIN structures come from the greater sciatic foramen and will hook behind the ischial spine in the gluteal region and go to the lesser sciatic foramen and continue towards the perineum region.

Muscles of the Gluteal Region (Abductor and Rotators of the Thigh)

In TRIO muscles, L5 root compression doesn't have any problem with hip adduction, but there is a problem in hip abduction. The Functions of TRIO muscles are:

• Abduction
• Medial rotation 
• Pelvic rotation & stabilisation

Gluteal maximus will antagonize the medial rotation. 

Third Action of the Trio Muscles

The TRIO muscles include Gluteus medius, Gluteus minimus and Tensor fascia latae. They help in Hip abduction, Medial rotation and Pelvic stabilization. While walking, one foot is in the air known as the swing phase of the walking cycle.

At that time, the other foot will be fixed to the ground known as the stance phase of the leg. Since one foot is taken out of the ground, gravity will pull the pelvis down. To prevent this, TRIO will have the function of pelvic stabilization. At this moment, origin and insertion will interchange. As the leg is fixed to the ground, femur cannot be moved down the hip bone and the origin becomes insertion. The TRIO muscle will pull the pelvis down so that the other side of the pelvis will move upwards with the help of vector, this is called the pelvic rotation to counteract the gravity. The vector is produced by the opposite (TRIO muscles) to maintain gravity. These muscles are supplied by the superior gluteal nerve.

If you have superior nerve injury, then the pelvis is not moved down, and the other pelvis will not move upwards as the vector is missing. Then the gravity will be powerful and pulling the other pelvis down, the Trendelenburg test will become positive. Then the patient has to drag the foot on the ground, and you cannot elevate it because limb length has become more. During the course of the disease, the patient will walk with the lurching gait.

Superior Gluteal Nerve

Anterior superior iliac spine (ASIS) on both sides will remain at the same level irrespective of the fact that which foot is in the air or on the ground.

If the right-sided TRIO muscles are not working then the patient is unable to pull the pelvis down then the other side of the pelvis will not be pulled up, especially while walking the foot comes into the air and the vector will be missing .Such that the gravity will not be maintained and the pelvis will sag on that side. Hence gravity moves the pelvis down whenever the patient is undergoing a swing phase.

In that condition, the lower limb will become long, and the patient will drag the foot to the ground.

After some time, patient can clear his foot from the ground if he is using a lurching gait.

In this condition, the Trendelenburg test will become positive because the ASIS line will not be at the same level (no straight line). In this condition, the doctor needs to place his thumb on the ASIS and ask the patient to take the foot off the ground, and if the ASIS falls down then the Trendelenburg test will become positive. To bring the pelvis back to normal, you need to bend the spine to the same side of the lesion. If the right-side muscles are not working, then the patients should bend the spine towards the right side so that the foot can be taken off the ground this is known as the lurching gait (patient will lurch towards the same side of the lesion). So that the ASIS will remain at the same level (straight line)

Frequently Asked Questions

Q1. Muscle attached to the lateral surface of greater trochanter

1. Gluteus maximus
2. Gluteus medius 
3. Gluteus minimus 
4. Piriformis

Answer: Gluteus Medius

Explanation 

• These gluteus muscles take their origin from the dorsal surface of the hip bone and inserted into the femur (moving of the femur)
• Gluteus maximus is the posterior muscle that attaches to the femur posteriorly. 
• Gluteus Medius is present in the middle region that attaches to the lateral surface of greater trochanter. 
• Gluteus minimus attaches to the greater trochanter anteriorly.
• Piriformis is attached to the tip of the trochanter on the superior surface

Q2. Injury to  nerve which passes superior to piriformis and winds around greater sciatic notch paralyses which muscle ?

1. Gluteus medius
2. Gluteus maximus
3. Obturator internus
4. Piriformis

Answer: Gluteus medius

Q3. In walking, gravity tends to tilt the pelvis and trunk to the unsupported side, a major factor in preventing this unwanted movement is

1. Adductor muscles
2. Quadriceps
3. Gluteus maximus
4. Gluteus medius and minimus

Answer: Gluteus medius and minimus

Explanation

• TRIO muscles include:
• Gluteus medius 
• Gluteus minimus 
• Tensor fascia latae

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