Learning Outcomes: Students will be able to:

1. Describe the musculoskeletal anatomy of the pelvis, sacroiliac, pubic symphysis, lumbosacral and hip joints and associated connective tissues that support these joints.
2. Identify the functional design of the pelvic girdle and hip joint and the osteokinematic and arthrokinematic movements
3. Describe the origin, insertion, actions, and nerve innervation of muscles that act on the pelvis and hip joints.
4. Describe sacroiliac joint sacral movements, pelvic girdle movements, and hip movements.
5. Identify how to strengthen and stretch each of the muscles or muscle groups that act upon the pelvic girdle and hip joint.
6. Describe Femoral Angle of Inclination and Femoral Angle of Torsion and the signs and symptoms associated with these pathologies.
7. Identify the mechanisms that can contribute to select pathologies of the hip and be able to describe their symptoms.

   Figure 1      

The bones of the pelvic girdle consist of two os coxae, or innominates, formed by the embryonic fusion of the ilium, ischium, and pubis.

The os coxae (innominates) are joined to the sacrum posteriorly at the sacroiliac joints, and to one another anteriorly at the pubic symphysis.. The pelvic girdle articulates with the fifth lumbar vertebra superiorly at the lumbosacral joint and inferiorly to the two femurs at the acetabulofemoral (hip) joints.

Pubis Symphysis (amphiarthrodial) – the junction between the

two pubic bones.

1. Fibrocartilage interpubic disc: this disc separates the

two pubic bones and during childbirth becomes softer

allowing more movement at the joint.

2. Superior Pubic Ligament: attaches to the pubic tubercles

on each side, strengthening the superior and anterior

portions of the joint. 

3. Inferior Pubic Ligament (Arcuate Pubic Ligament):

Attaches to the two inferior pubic rami, strengthening

the inferior portion of the joint.

4. Fibrous aponeurotic expansions of the abdominal wall

also help strengthen and stabilize this joint.

Figure 2

Sacroiliac (SI) Joints (arthrodial) –  the junction between the

“auricular” surfaces of the sacrum and the “auricular” surfaces

of the ilium. The function of the sacroiliac joint is to transmit weight

from the upper body through the vertebral column to the hips and

femurs. The sacroiliac ligaments support the SI joint on the anterior

and posterior surfaces of the joint.

1. Short Posterior Sacroiliac Ligament: attaches from the

posterior surface of the upper sacrum to the posterior

surface of the ilium.

2. Long Posterior Sacroiliac Ligament: runs vertically

from the posterior superior iliac spine to the lower

sacrum.

3. Anterior Sacroiliac Ligament: attaches from the anterior

surface of the sacrum and ala to the auricular surface of

ilium, stabilizing the anterior surface of the joint.

4. Sacrotuberous Ligament: a triangular ligament that

attaches from the sacrum to the ischial tuberosity.

5. Sacrospinous Ligament: a triangular ligament that

attaches from the sacrum to the ischial spine.

Figure 3

Sacroiliac Joint Motion

The actual type and amount of movement occurring at the SI joint is controversial. However, it is generally accepted that only a very small amount of movement (1-3 mm) occurs, it must be in conjunction with other motions, and is described as nutation or counternutation.

•  Nutation: Sometimes called sacral flexion, occurs when the base of the sacrum (superior part) moves anteriorly and inferiorly, and the apex (inferior part) moves posteriorly and superiorly.  

• Occurs with end range trunk flexion or hip extension

• Counternutation: Sometimes called sacral extension, occurs when the base (superior) of the sacrum moves posteriorly and superiorly, and the apex (inferior) moves anteriorly and inferiorly.

• Occurs with end range trunk extension or hip flexion

Note: In the initial moments of these movements the sacrum actually moves opposite of what is stated, but as soon as the joint ligaments become taut the sacrum follows the pelvis and spine.

Lumbosacral Joint

The lumbosacral joint is the articulation between the sacrum and L5 vertebra (L5-S1 spinal segment). Movement of the pelvis at the lumbosacral joint is limited. When the pelvis moves at the lumbosacral joint, the rest of the spine will begin to move once the motion at the lumbosacral joint has reached its limit. In addition to the spinal ligaments, this joint is also supported by:

• Iliolumbar ligament: attaches from the transverse process of L5 running laterally to the inner lip of the posterior portion of the iliac crest. Limits rotation of L5 on S1, and prevents L5 from anterior displacement.

• Lumbosacral : attaches from the transverse process of L5 running laterally and inferiorly to the ala of the sacrum, also limiting L5 anterior displacement.

Figure 5

Pelvic Girdle Movements

The joints directly involved in pelvic girdle movement include the two hip joints and the lumbosacral joint. Because the axial skeleton attaches to the pelvis through the sacroiliac joint, movement of the pelvis in relationship to the hip also influences spinal movements.

In good posture the anterior superior iliac spine (ASIS) and the pubic symphysis are in the same vertical plane, known as spine neutral or neutral spine.

 Figure 6    

Sagittal Plane Movement

Anterior Pelvic Rotation: occurs when the pelvis rotates forward, moving the ASIS anterior to the pubic synthesis, decreasing the angle between the pelvis and the femoral shafts, resulting in closed chain hip flexion. A force couple is creating by the simultaneous contraction of the hip flexors and trunk extensors.

• Spinal extension occurs increasing lumbar lordosis

                   Figure 7

Anterior Pelvic Tilt: Tilt reflects a postural fault due to muscular imbalance: tight hip flexors and low back extensors, weak trunk flexors and hip extensors.

Posterior Pelvic Rotation: occurs when the pelvis rotates backward, moving the ASIS posterior to the pubic synthesis, increasing the angle between the pelvis and the femoral shafts, resulting in closed chain hip extension. A force couple is created by the simultaneous contraction of the hip extensors and trunk flexors.

• Spinal flexion occurs decreasing lumbar lordosis curve

                Figure 8

Posterior Pelvic Tilt: Tilt reflects a postural fault due to muscular imbalance: tight hip extensors and trunk flexors, weak hip flexors and low back extensors.

Frontal Plane Movement

Left Lateral Pelvic Rotation: the right pelvis is elevated while the left moves inferiorly, resulting in left hip abduction and right hip adduction.

• Right lateral flexion of the trunk occurs

   Figure 9            Front View

Right Lateral Pelvic Rotation: the left pelvis is elevated/hiked rotating the pelvis toward the right as it moves inferiorly, resulting in right hip abduction and left hip adduction.

• Left lateral flexion of the trunk occurs

      Figure 10    Front View

Transverse Plane Movement

Left Transverse Pelvic Rotation: With rotation of the pelvis to the body’s left, the right iliac crest moves anteriorly in relation to the left iliac crest, which moves posteriorly.  Closed chain right hip external rotation and left hip internal rotation occur during left transverse pelvic rotation.

Figure 11

Right Transverse Pelvic Rotation: With rotation of the pelvis to the body’s right, the left iliac crest moves anteriorly in relation to the right iliac crest, which moves posteriorly. Closed chain right hip external rotation and left hip internal rotation occur during left transverse pelvic rotation.

Figure 12

Acetabulofemoral (enarthrodial- triaxial)

Closed Pack Position: Fully extended, internally rotated, and abducted

Open Pack Position: Flexed 30º and abducted 30º

1. Acetabular Labrum: a fibrocartilaginous ring of tissue that surrounds the circumference of the acetabulum increasing the depth of the socket and the joint stability.

2. Transverse Acetabular Ligament: Because the acetabulum does not form a complete ring at the hip joints inferior margin its two ends are connected by the transverse acetabular ligament.

3. Ligamentum Teres: attaches from the internal surface of the acetabulum to the fovea capitus on the head of the femur.

--Primarily provides a conduit for the blood vessels and nerves to the femoral.

4. Iliofemoral “Y” Ligament: attaches from the anterior inferior iliac spine (AIIS) and the posterosuperior aspect of the brim of the acetabulum. It splits into two parts crossing the hip anteriorly to attach to the intertrochanteric line of the femur.

--Limits hip hyperextension

5. Pubofemoral Ligament: attaches from the medial aspect of the acetabular rim and lateral aspect of the superior ramus of the pubis to femoral neck and center portion of the intertrochanteric line of the femur.

--Limits hip hyperextension and abduction 

6. Ischiofemoral Ligament: attaches from the ischial portion of the acetabulum to the femoral neck.

--Limits hip internal rotation & hip hyperextension

 Figure 13

  Figure 14

Figure 15

Hip Joint Movements

Hip Flexion: Anterior movement of the femur in the sagittal plane

Hip Extension: movement of the femur straight posteriorly from any point in the sagittal plane away from the pelvis

Hip Abduction: Lateral movement of the femur in the frontal plane away from the body midline

Hip Adduction: Medial movement of the femur in the frontal plane toward the body midline

Hip External Rotation: Lateral rotary movement of the femur in the transverse plane around its longitudinal axis away from the body midline

Hip Internal Rotation: Medial rotary movement of the femur in the transverse plane around its longitudinal axis toward the body midline

Hip Joint Range of Motion

Flexion: 120° (knee flexed)

                90° (knee extended)

Extension: 30° 

Abduction: 45°

Adduction: 30°

Internal Rotation: 45°

External Rotation: 45°   

Femoral Angle of Inclination

Femoral Angle of Torsion

The angle between the shaft of the femur and the neck of the femur in the transverse plane. Normally the head is rotated anteriorly (anteverted) from the shaft approximately 15º.  

• Anteversion: When the angle is increased (significantly >15º) and can result in a “toeing in” position during standing and walking and can restrict lateral rotation ROM at the hip.
• Retroversion: When the angle is decreased (significantly <8º) and can result in a “toeing out” position during standing and walking and can restrict medial rotation ROM at the hip.

  Figure 17          

Muscle Innervation & Cutaneous Distribution

Muscles of the Hip Joint

Anterior – primarily hip flexion

• Iliacus
• Psoas (major & minor)
• Pectineus
• Rectus Femoris
• Sartorius

Posterior – primarily hip extension

• Gluteus maximus
• Semitendinosus
• Semimembranosus
• Biceps femoris
• 6 External Rotators

Lateral – primarily hip abduction

• Tensor fasciae latae
• Gluteus medius
• Gluteus minimus

Medial – primarily hip adduction

• Adductor brevis
• Adductor longus
• Adductor magnus
• Gracilis

Muscles of the Anterior Hip

 Figure 22

Figure 23

Figure 24

Muscles of the Lateral Hip

Figure 26

Deep 6 External Rotators

1. Piriformis
2. Gemellus Superior
3. Obturator Internus
4. Gemellus Inferior
5. Obturator Externus
6. Quadratus Femoris

Origin: Anterior sacrum, posterior portions

  of the ischium and obturator foreman

Insertion: Superior and posterior aspect of

  the greater trochanter of the femur

Action: Hip external rotation

Nerve: Branches of the sacral plexus and

  the obturator nerve

       Figure 27  

Piriformis Syndrome

Description: Compression of the sciatic nerve (L4-S2) as it passes under (or through) the Piriformis causing pain to radiate into the buttock and distally along the course of the sciatic nerve.

How to locate Piriformis: ½ distance between PSIS & sacral apex. Drop off edge of sacrum → lies between edge and greater trochanter.

 Figure 28     

Muscles of the Posterior Hip

Figure 29

Figure 30

Muscles of the Medial Hip

Figure 31

Hip Flexion & IT Band Tightness Tests

Tight Hamstrings

Pelvis and Hip Joint Review Questions