Learning Outcomes: Students will be able to:
- Describe the musculoskeletal anatomy of the pelvis, sacroiliac, pubic symphysis, lumbosacral and hip joints and associated connective tissues that support these joints.
- Identify the functional design of the pelvic girdle and hip joint and the osteokinematic and arthrokinematic movements
- Describe the origin, insertion, actions, and nerve innervation of muscles that act on the pelvis and hip joints.
- Describe sacroiliac joint sacral movements, pelvic girdle movements, and hip movements.
- Identify how to strengthen and stretch each of the muscles or muscle groups that act upon the pelvic girdle and hip joint.
- Describe Femoral Angle of Inclination and Femoral Angle of Torsion and the signs and symptoms associated with these pathologies.
- Identify the mechanisms that can contribute to select pathologies of the hip and be able to describe their symptoms.
The pelvic girdle is located between the trunk (lumbar area) and the thighs (femurs). The pelvic girdle functions primarily to provide stability and support for the upper body and transmits upper body weight to the lower limbs when standing (or to the ischial tuberosity when sitting). It also contributes to walking by providing a sturdy base for trunk and lower extremity muscles to move the more distal segments (distal mobility and proximal stability).
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.
- Fibrocartilage interpubic disc: this disc separates the
two pubic bones and during childbirth becomes softer
allowing more movement at the joint.
- Superior Pubic Ligament: attaches to the pubic tubercles
on each side, strengthening the superior and anterior
portions of the joint.
- Inferior Pubic Ligament (Arcuate Pubic Ligament):
Attaches to the two inferior pubic rami, strengthening
the inferior portion of the joint.
- Fibrous aponeurotic expansions of the abdominal wall
also help strengthen and stabilize this joint.
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.
- Short Posterior Sacroiliac Ligament: attaches from the
posterior surface of the upper sacrum to the posterior
surface of the ilium.
- Long Posterior Sacroiliac Ligament: runs vertically
from the posterior superior iliac spine to the lower
- 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.
- Sacrotuberous Ligament: a triangular ligament that
attaches from the sacrum to the ischial tuberosity.
- Sacrospinous Ligament: a triangular ligament that
attaches from the sacrum to the ischial spine.
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.
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.
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.
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
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
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.
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.
Open Chain Pelvofemoral Motions
Hip Flexion: will be accompanied by ipsilateral posterior pelvic rotation to allow further hip flexion ROM, and contralateral anterior pelvic rotation.
Hip Extension: will be accompanied by ipsilateral anterior pelvic rotation to allow further hip extension ROM, and contralateral posterior pelvic rotation.
Acetabulofemoral (enarthrodial- triaxial)
Closed Pack Position: Fully extended, internally rotated, and abducted
Open Pack Position: Flexed 30º and abducted 30º
The acetabulofemoral joint is the articulation between the acetabulum of the os coxa/innominate and the head of the femur. Being an enarthrodial joint, it is surrounded by a fibrous joint capsule that provides significant stability for the joint. To help further strengthen this joint the capsule contains strong circular deep fibers called the zona orbicularis that surround the neck of the femur. In addition, three strong capsular ligaments reinforce the hip joint anteriorly.
- Acetabular Labrum: a fibrocartilaginous ring of tissue that surrounds the circumference of the acetabulum increasing the depth of the socket and the joint stability.
Note: With hip problems, pain is often manifested in the anterior groin area and may be referred to the knee.
- 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.
- 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.
- 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
- 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
- Ischiofemoral Ligament: attaches from the ischial portion of the acetabulum to the femoral neck.
--Limits hip internal rotation & hip hyperextension
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)
Internal Rotation: 45°
External Rotation: 45°
Femoral Angle of Inclination
The angle between the femoral neck and femoral shaft. In infants this angle may be around 160º, but by adulthood normally averages 125º.
- Coxa Vara: describes an abnormal decrease in the angle of inclination (<120 degrees).
- Coxa Valga: describes an abnormal increase in the angle of inclination (>135 degrees
These changes alter the alignment of a muscle’s line of pull and can lead to decreased muscle strength due to changes in the length of the muscular force arm. This malalignment can also increase joint stress and lead to joint dysfunction. Specifically:
- Coxa Vara is associated with femoral growth plate changes and adolescent hip disorders. May be seen in older adults with osteoarthritis (OA) and/or osteoporosis. Often leads to genuvalgum and overpronation of the foot/ankle.
- Coxa Valga reduces the femoral joint congruency resulting in joint instability and an increased risk of hip dislocations. Often associated with genuvarum and overpronation of the foot/ankle.
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.
Muscle Innervation & Cutaneous Distribution
Figures 18, 19, 20, 21
Muscles of the Hip Joint
Anterior – primarily hip flexion
- Psoas (major & minor)
- Rectus Femoris
Posterior – primarily hip extension
- Gluteus maximus
- 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
Muscles of the Anterior Hip
Muscles of the Lateral Hip
Tensor Fascia Latae
Deep 6 External Rotators
- Gemellus Superior
- Obturator Internus
- Gemellus Inferior
- Obturator Externus
- 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
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.
Muscles of the Posterior Hip
Muscles of the Medial Hip
Hip Flexion & IT Band Tightness Tests
- Thomas Test (tight hip flexors, non-specific): Patient in supine position. While leaving the test leg on the table the opposite leg is flexed towards chest and held there with hands.
- Positive Test: If test knee/leg raises off table.
- Modified Thomas Test (distinguishing between Iliopsoas complex and Rectus Femoris tightness): Perform Thomas Test at the end of the table with test leg hanging off the edge.
- Positive Test: If when the non-test knee is brought to the chest the test knee extends, then Rectus Femoris tightness is present.
- Ober’s Test (tight Tensor Fascia Latae): Patient is side-lying with back close to table’s edge. Down leg hip and knee are flexed approx. 45°. Examiner passively abducts and extends leg so the TFL is over the greater trochanter.
- Positive Test: If leg does not drop down to anatomic position or adduction, but is restricted in abducted position.
- 90-90 Straight Leg Raise Test (hamstring tightness): Patient is positioned supine. Leg to be tested is brought to 90° hip flexion with knee in flexed position. Then the knee is extended as far as possible.
- Positive Test: At end point the knee is more than 20° flexed.
Pelvis and Hip Joint Review Questions
- What is the difference between a pelvic rotation and a pelvic tilt in the sagittal plane?
- What is the relationship between the ASIS and pubic symphysis in spine neutral? In anterior pelvic tilt?
- What is the difference between stretching the rectus femoris in the prone vs supine position?
- You stand on a step with your right foot positioned “parallel” on the step and your other foot is hanging off the
Step. You then hike or elevate your hip on the side hanging off the side of the step. When doing this movement,
what hip movement is being performed on the side that is hanging off and what hip movement is being performed on
the opposite side?
- What three muscles attach on the medial border of the tibia just below the medial tibial condyle?
- In what direction is the arthrokinematic roll during hip extension?
- During walking, in which direction, right or left, will your pelvic rotate when your right leg swings forward?
- A posterior pelvic rotation is a force couple movement involving which two muscle groups?
- What is the prime mover for hip abduction?
- Describe the movement of the sacrum during sacral nutation?