The External Rotators

Fig 1. Deep external rotators. Illustration by Prue Schafferius

The External Rotators

This is the collective name of a group of six deep muscles responsible for the action of external rotation of the hip/femur.

These muscles are also crucial for hip health. Poor functioning external rotators can cause incorrect leg alignment, tendonitis/over use injuries, general hip pain, bursitis (inflammation of the bursa), less stability through the hip joint and wear and tear on the joint. Obturator internus and the gemelli in particular, have a decompressive effect on the hip joint, very slightly pulling the head of the femur away from the acetabulum, which in turn relieves pain in those experiencing osteo-arthritis of the hip.

Healthy hip function for Bellydancers is essential to prevent wear on the lubrum and the joint. Stretches and exercises for hip health will be covered in the BODY CONDITIONNG course.

The six deep rotators originate from different areas on the pelvis but all insert on or near the greater trochanter.

Piriformis

Originates on the anterior sacrum. It passes under the sciatic notch and inserts on the top of the greater trochanter. This muscle also sits on top of the sciatic nerve, meaning that a tight piriformis can cause issues with the sciatic nerve. This condition is called sciatica and will be covered in the INJURY MANAGEMENT course.

Actions from the anatomical position

• If the sacrum is fixed (still) piriformis externally rotates and abducts the femur.
• If the femur is fixed, piriformis adds to extension of the pelvis and internal rotation of the pelvis.

Quadratus femoris (QL)

Originates from the lateral ischium, runs horizontally and inserts onto the posterior aspect of the greater trochanter.

Actions

• When the pelvis is fixed, QL externally rotates the femur.
• With the femur fixed, QL contributes to extension of the pelvis and medial rotation of the pelvis

Qbturator internus

Originates from the ischium and ilium, passing posteriorly through the lesser sciatic notch, making a turn around the body of the ischium and then inserting on the medial aspect of the greater trochanter. A bursa (sack of fluid) at the point where the obturator internus wraps around the ischium. This bursa reduces friction at the point of contact between muscle and bone.

Actions

• If the pelvis is fixed, this muscle acts on external rotation and abduction of the femur.
• If the femur is fixed, obturator internus acts on extension and medial rotation of the pelvis.

Obturator externus

This muscle arises from the external surface of the obturator membrane. It then passes behind the neck of the femur, and inserts on the medial surface of the greater trochanter.

Actions

• If the pelvis is fixed, it acts on external rotation and abduction of the femur.
• If the femur is fixed, it is a flexor of the pelvis. It also medially rotate the pelvis.

Gemellus superior and inferior

These are small muscles located above and below the obturator internus.

Actions

• Their actions are the same as obturator internus.

Psoas and Iliacus

Fig 2. Psoas and Iliacus. Illustration by Prue Schafferius

Psoas

The actions of the psoas on the spine, were previously discussed in THE TRUNK AND SPINE module. This muscle also acts on the movements of the pelvis. The psoas originates from the vertebral bodies of T12-L5. The fibres run anterior to the pelvis and inserts on the lesser trochanter. A bursa to reduce friction is located where the muscle bends on the anterior pelvis.

Actions from the anatomical position

• When the vertebrae are fixed, the psoas flexes the hip as well as a weak adductor and external rotator.

Iliacus

While the iliacus joins the psoas to insert through the same tendon on the lesser trochanter, it originates from the entire internal iliac fossa rather than the lumbar spine.

Actions from the anatomical position

• When the pelvis is fixed, the iliacus joins the psoas in flexion of the femur.
• When the femur is fixed, the iliacus acts in flexion of the pelvis. (sticking the bottom out) Note; because of its origins on the pelvis, the iliacus does not act on the spine like the psoas.

Lateral Muscles of the Hips

Fig 3. Gluteus maximus, medius, minimus posterior view.

Fig 4. Gluteus medius and gluteus minimus lateral view.

Fig 5. Tensor fasciae lata and gluteus maximus lateral view.

Illustrations by Prue Schafferius

Lateral Muscles of the Hips

The following muscles are important for a Bellydancer to be able to execute movements such as chonks, shimmies, hip drops and lifts to name just a few! They are also easily overworked if the external rotators are lacking in strength. As there is a bursa located on the lateral aspect of the greater trochanter, it is quite easy to fall into a pattern of overworking these lateral glutes and inflaming the bursa, leading to pain that is often poorly treated by health professionals. We will cover how to overcome this particular problem in the INJURY MANAGEMENT course.

Gluteus medius

This muscle has a broad origin on the external iliac fossa. Its fibers draw closer together as they insert on the side of the greater trochanter.

Actions from the anatomical position

• When the pelvis is fixed, the glute med is acts on abduction of the femur.
• However, when the femur is fixed, the glute med is involved in flexion and extension of the pelvis (also known as anterior and posterior tilt, or sticking the bottom 'out' and tucking it 'under'.)
• Lateral flexion of the pelvis is also performed by (hip lifts, drops, chonks etc)

Gluteus minimus

This is a small muscle that originates from the iliac fossa and inserts on the anterior side of the greater trochanter.

Actions from the anatomical position

• When the femur is fixed, the glute min acts on abduction of the femur.
• The glute min also contributes to flexion of the pelvis (anterior tilt)
• Along with glute med, glute min also acts on lateral flexion of the pelvis (hip drops, lifts, chonks, 3/4 shimmy etc)

Tensor fasciae latae (TFL)

The TFL originates from the iliac crest (at the top, on the lateral side of the pelvis) This muscle runs down the side of the hip and does not insert onto bone, but onto a long, strong band of fibrous tissue called the Iliotibial tract or band. Often called the ITB, this band runs down the lateral side of the femur and attaches to the superlateral tibia and the head of the fibula.

The ITB plays an important role in the function and stability of the knee. This will be detailed in THE KNEE module.

Actions from the anatomical position

• The TFL has the same roles as the glute med and glute min; abduction, internal rotation and some flexion of the femur.
• When the femur is fixed; anterior tilt and lateral flexion of the pelvis.
• The TFL also plays a small part in lateral rotation of the flexed knee (twisting the knee outwards when it is bent)

Gluteus Maximus

Fig 6. Gluteus maximus posterior view. Illustration by Prue Schafferius

Gluteus Maximus

This well known muscle is one of the largest and strongest muscles in the body. It consists of a deep layer as well as a superficial layer.

The glute max, arises on the posterior sacrum and coccyx as well as a little from the pelvis (ilium). The deep layer inserts on the back of the femur, while the superficial layer inserts into the TFL. The superficial layer along with the TFL, can be described as the 'pelvic deltoid muscle'. These two muscles insert onto the ITB from opposite directions,

Actions from the anatomical position

Deep layer

• When the pelvis is fixed, the deep layers of glute max pull the femur into extension as well as external rotation.
• When the femur is fixed, the glute max acts on extension of the pelvis (posterior tilt, or tucking the bottom 'under')

Superficial layer

• Acts on the femur in extension, external rotation and abduction.
• When the femur is fixed, it assists in lateral flexion of the pelvis.

TFL and superficial glute max

• Act together on abduction of the femur.

Other Hip Flexor Muscles

Fig 7. Sartorius anterior view.

Fig 8. Rectus femoris anterior view.

Fig 9. Rectus femoris lateral and medial view.

Illustrations by Prue Schafferius

Other Hip Flexor Muscles

Sartorius

The sartorius is the longest muscle in the body. It begins on the ASIS (the bony bit that sticks out at the front of the pelvis) and runs diagonally down and across the thigh towards and inserts on the medial side of the tibia. This muscle crosses both the hip and the knee joint.

Actions from the anatomical position

• When the pelvis is fixed, sartorius acts on flexion, external rotation, and abduction of the femur.
• It also acts on medial rotation of the tibia (twisting the lower leg inwards)

Rectus femoris

This muscle is part of the quadriceps femoris group, otherwise known as the quads. We will look at these muscles in more detail in THE KNEE module. The rectus femoris is the only muscle in this group to cross both the hip and the knee joints. It arises from the just above the anterior side of the acetabulum on the anterior inferior iliac spine. It passes over the top of the quads and inserts into the quadriceps tendon. This tendon surrounds the patella (knee cap) and then turns into the patella ligament which inserts onto the the top of the tibia on the tibial tuberosity.

Actions from the anatomical position

• The rectus femoris acts on both the knee and the hip.
• When the pelvis is fixed, it acts on flexion of the femur.
• When the femur is fixed, it acts on flexion of the pelvis (anterior tilt, sticking the bottom out)

The Hamstrings

Fig 10. The hamstrings posterior view. Illustration by Prue Schafferius

The Hamstrings

The hamstrings are a group of three muscles located on the posterior side of the thigh. They work together to both extend the femur and bend the knee. The hamstrings originate on the ischial tuberosity (the sitting bone) and insert onto the the tibia and fibula.

Semimembranosus is the deepest of the three muscles. It inserts on the back of the tibial condyle on the posterior medial aspect.

Semitendinosus is located on top of the semimembranosus. It inserts into the supermedial aspect of the tibial shaft via a long tendon.

Biceps femoris is located laterally to the other two hamstrings. It has two heads that merge and insert into one tendon which inserts into the fibula.

Actions from the anatomical position

• When the pelvis is fixed, the hamstrings act on extension of the femur.
• When the femur is fixed, the hamstrings act on extension/ posterior tilt of the pelvis ('tucking' the bottom under)
• The actions of the hamstrings on the knee will be discussed in THE KNEE module.

The Adductor/ Inside Thigh Muscles

Fig 11. The adductors anterior view.

Fig 12. Adductor magnus.

Illustrations by Prue Schafferius

The Adductor/Inside Thigh Muscles

The adductors are a group of five muscles that are located on the medial thigh. They all have the same action of adduction of the femur enough though they have different insertion points.

Pectineus runs from the lateral pubis (just next to the pubic symphysis) and inserts just below the lesser trochanter and the femur.

Adductor brevis originates from the medial pubis to the the mid part of the femur.

Adductor longus originates medially on the pubis. It runs over the adductor brevis and inserts lower on the medial femur.

Adductor magnus is the strongest and largest adductor muscle. It consists of two portions that originate and insert on different parts of the inferior femur. The anterior portion originates on the ischiopubic ramus and runs diagonally, inserting on the linea aspera of the femur. The posterior portion arises from the ischial tuberosity and runs straight down where it inserts on the medial femoral condyle.

Gracilis is a long muscle that runs from the inferonmedial pubis and inserts on the the tibia, just below the knee on the medial condyle. This muscle crosses both the hip and the knee. See the video below to discover how this affects flexibility.

Actions from the anatomical position

The adductors primarily adduct the the thigh, bringing the leg from an abducted position back towards the midline, or taking the leg across the midline.

But they can also act from the anatomical position as hip flexors or lateral or medial rotators. If the femur is already in flexion, they can act on extension of the femur.