HIPDr. Michael P. Gillespie

OSTEOLOGY Each innominate is the union of three bones: the

ilium, pubis, and ischium. The right and left innominates connect with each

other anteriorly at the pubic symphysis and posteriorly at the sacrum.

An osteoligamentous ring known as the pelvis (Latin: basin or bowel) is formed.

Functions of the pelvis: Attachment point for many muscles of the lower

extremity and trunk. Transmits the weight of the upper body and trunk to

the ischial tuberosities during sitting and to the lower extremities during standing or walking.

Supports the organs of the bowel, bladder, and reproductive system.

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INNOMINATE

Ilium Pubis Ischium Acetabulum

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EXTERNAL SURFACE OF THE PELVIS

Wing (ala) – the large fan-shaped wing of the ilium forms the superior half of the innominate.

Acetabulum – a deep, cup-shaped cavity below the wing.

Obturator-foramen – the largest foramen in the body. Covered by the obturator membrane.

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OSTEOLOGIC FEATURES OF THE ILIUM External Surface

Posterior, anterior, and inferior gluteal lines

Anterior-superior iliac spine

Anterior-inferior iliac spine

Iliac crest Posterior-superior iliac

spine Posterior-inferior iliac

spine Greater sciatic notch Greater sciatic foramen Sacrotuberous and

sacrospinous ligaments

Internal Surface Iliac fossa Auricular surface Iliac tuberosity

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OSTEOLOGIC FEATURES OF THE PUBIS

Superior pubic ramus Body Crest Pectineal line Pubic tubercle Pubic symphysis joint and disc Inferior pubic ramus

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OSTEOLOGIC FEATURES OF THE ISCHIUM

Ischial spine Lesser sciatic notch Lesser sciatic foramen Ischial tuberosity Ischial ramus

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ANTERIOR ASPECT: PELVIS, SACRUM, RIGHT PROXIMAL FEMUR

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LATERAL VIEW RIGHT INNOMINATE BONE

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POSTERIOR ASPECT OF PELVIS, SACRUM, & PROXIMAL FEMUR

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FEMUR The longest and strongest bone in the human body. The femoral head projects medially and slightly

anterior to articulate with the acetabulum. The femoral neck connects the head with the shaft. The neck displaces the proximal shaft of the femur

laterally away from the joint, thereby reducing the likelihood of bony impingement.

Distal to the neck, the shaft of the femur courses slightly medially, placing the knees and feet closer to the midline of the body.

The femur bows slightly when subjected to the weight of the body. Stress along the bone is dissipated through compression along the posterior shaft and through tension along the anterior shaft.

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OSTEOLOGIC FEATURES OF THE FEMUR

Femoral Head Femoral Neck Intertrochanteric

Line Greater trochanter Trochanteric fossa Intertrochanteric

crest Quadrate tubercle

Lesser trochanter Linea aspera Pectineal (spiral)

line Gluteal tuberosity Lateral and medial

supracondylar lines Adductor tubercle

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ANTERIOR ASPECT RIGHT FEMUR

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MEDIAL & POSTERIOR SURFACES RIGHT FEMUR

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ANGLE OF INCLINATION The angle of inclination of the proximal femur

describes the angle within the frontal plane between the femoral neck and the medial side of the femoral shaft.

At birth this angle is about 140 – 150 degrees; however, the loading across the femoral neck during walking usually decreases this to the normal adult value of about 125 degrees.

Coxa = hip, vara = to bend inward, valga = to bend outward

Coxa vara – an angle of inclination markedly less than 125 degrees.

Coxa valga – an angle of inclination markedly greater than 125 degrees.

Abnormal angles can lead to dislocation or stress-induced degeneration of the joint.

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ANGLE OF INCLINATION

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FEMORAL TORSION Femoral torsion describes the relative rotation

(twist) between the bone’s shaft and neck. Normally, as viewed from above, the femoral

neck projects about 15 degrees anterior to a mid-lateral axis through the femoral condyles (normal anteversion).

Femoral torsion significantly different than 15 degrees is considered abnormal.

Excessive anteversion – significantly greater than 15 degrees

Retroversion – approaching 0 degrees Healthy infants are born with about 40

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EXCESSIVE FEMORAL ANTEVERSION Excessive anterversion that persists into adulthood can

increase the likelihood of hip dislocation, articular incongruence, increase joint contact force, and increased wear on the cartilage.

This can lead to secondary osteoarthritis of the hip. It may be associated with an abnormal gait pattern called

“in-toeing”, a walking pattern with exaggerated posturing of hip internal rotation.

The amount of “in-toeing” is generally related to the amount of femoral anteversion.

It is a compensatory mechanism used to guide the excessively anteverted femoral head more directly into the acetabulum.

Over time, shortening of the internal rotator muscles and ligaments occurs, thereby reducing external rotation.

Most children with in-toeing eventually walk normally. Excessive femoral anteversion is common in persons with

cerebral palsy. It typically does not resolve in this population.

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NORMAL ANTEVERSION

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EXCESSIVE ANTEVERSION

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RETROVERSION

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INTERNAL ROTATION IMPROVING JOINT CONGRUITY

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IN-TOEING

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FUNCTIONAL ANATOMY OF THE HIP JOINT

The hip is a classic ball-and-socket joint secured within the acetabulum by an extensive set of connective tissues and muscles.

Articular cartilage, muscle, and cancellous bone in the proximal femur help dampen the large forces that cross the hip.

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FEMORAL HEAD

The head of the femur forms about two-thirds of a nearly perfect sphere.

The entire surface of the femoral head is covered by articular cartilage except for the region of the fovea, which is slightly posterior to the center of the head.

The fovea is a prominent pit that serves as the attachment point for the ligamentum teres.

The ligamentum teres is a tubular sheath that runs between the transverse acetabular ligament and the fovea of the femoral head. It is a sheath that contains the acetabular artery.

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ACETABULUM The acetabulum (Latin – vinegar cup) is a deep,

hemispheric cuplike socket that accepts the femoral head.

The femoral head contacts the acetabulum along the horseshoe-shaped lunate surface, which is covered with thick articular cartilage.

During walking, hip forces fluctuate from 13% of body weight to over 300% of body weight during the mid-stance phase.

During stance phase, the lunate surface flattens slightly as the acetabular notch widens. This serves as a dampening mechanism to reduce peak pressure.

The acetabular fossa is a depression located deep within the floor of the acetabulum. It does not normally come into contact with the femoral head.

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HIP JOINT COMPRESSION AS A PERCENT OF GAIT CYCLE

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ANATOMIC FEATURES OF THE HIP JOINT

Femoral Head Fovea Ligamentum teres

Acetabulum Acetabular notch Lunate surface Acetabular fossa Labrum Transverse acetabular ligament

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INTERNAL ANATOMY OF HIP JOINT

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ACETABULAR LABRUM The acetabular labrum is a flexible ring of

fibrocartilage that surrounds the outer circumference (rim) of the acetabulum.

The acetabular labrum projects about 5 mm toward the femoral head.

It provides significant stability to the hip by “gripping” the femoral head and deepening the volume of the socket by approximately 30%.

The seal formed by the labrum maintains a negative intra-articular pressure, thereby creating a modest suction that resists distraction of the joint surfaces.

It also helps to hold synovial fluid within the joint space.

It decreases the contact stress (force / area) by increasing the surface area of the acetabulum.

Poor blood supply – limited ability to heal Well supplied with afferent nerves – proprioceptive

feedback / pain

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ACETABULAR ALIGNMENT

In the anatomic position, the acetabulum typically projects laterally from the pelvis with a varying amount of inferior and anterior tilt.

Congenital or developmental conditions can result in an abnormally shaped acetabulum.

A dysplastic acetabulum that does not adequately cover the femoral head can lead to chronic dislocation and increased stress, which can lead to osteoarthritis.

Two measurements are used to describe the extent to which the acetabulum naturally covers and helps to secure the femoral head: Center-edge angle Acetabular anteversion angle

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CENTER-EDGE ANGLE

The center-edge angle varies widely, but on average measures about 35 degrees in adults.

A significantly lower center-edge angle reduces the acetabular coverage of the femoral head. This increases the risk of dislocation and reduces contact area within the joint.

During the single-limb-support phase of walking, this reduced surface area would increase joint pressure (force / area) by about 50%.

This increased joint pressure can lead to premature osteoarthritis.

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CENTER-EDGE ANGLE

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ACETABULAR ANTEVERSION ANGLE The acetabular anteversion angle measures

the extent to which the acetabulum projects anteriorly within the horizontal plane, relative to the pelvis.

Observed from above, the normal acetabular anteversion angle is about 20 degrees, which exposes part of the anterior side of the femoral head.

A hip with excessive acetabular anteversion is more exposed anteriorly.

When anteversion is severe, the hip is more prone to anterior dislocation and associated lesions of the labrum. 34

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ACETABULAR ANTEVERSION ANGLE

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CAPSULE AND LIGAMENTS OF THE HIP

A synovial membrane lines the internal surface of the hip joint capsule.

The iliofemoral, pubofemoral, and ischiofemoral ligaments reinforce the external surface of the capsule.

Passive tension in the stretched ligaments, the adjacent capsule, and the surrounding muscles help to define end-range movements of the hip.

Increasing the flexibility of parts of the capsule is an important component of manual physical therapy for restricted movement of the hip.

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ANTERIOR CAPSULE & LIGAMENTS

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POSTERIOR CAPSULE & LIGAMENTS

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PARAPLEGIC WITH SUPPORT BRACES

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TISSUES THAT BECOME TAUT AT THE END-RANGES OF PASSIVE HIP MOTION

End-Range Position Taut Tissue

Hip flexion (knee extended) Hamstrings

Hip flexion (knee flexed) Inferior and posterior capsule; gluteus maximus

Hip extension (knee extended) Primarily iliofemoral ligament, some fibers of the pubofemoral and ischiofemoral ligaments; psoas major

Hip extension (knee flexed) Rectus femoris

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TISSUES THAT BECOME TAUT AT THE END-RANGES OF PASSIVE HIP MOTION

End-Range Position Taut Tissue

Abduction Pubofemoral ligament; adductor muscles

Adduction Superior fibers of ischiofemoral ligament; iliotibial band; and abductor muscles such as the tensor fascia latae and gluteus maximus

Internal rotation Ischiofemoral ligament; external rotator muscles, such as the piroformis or gluteus maximus

External rotation Iliofemoral and pubofemoral ligaments; internal rotator muscles, such as the tensor fascia latae or gluteus minimus

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CLOSE-PACKED POSITION OF THE HIP

Full extension of the hip (about 20 degrees beyond neutral) in conjunction with slight internal rotation and slight abduction twists or “spirals” the fibers of the capsular ligaments to their most taut position.

This is considered the close-packed position of the hip.

The passive tension leads to stability of the joint and reduces “joint play”.

The hip joint is one of the few joints in the body where the close-packed position is NOT also the position of maximal joint congruency. They fit most congruently in about 90 degrees of flexion, moderate abduction, and external rotation.

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NEUTRAL AND CLOSED PACKED POSITIONS

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OSTEOKINEMATICS Reduced hip motion may be an early indicator of

disease or trauma. Limited hip motion can impose functional

limitations on activities such as walking, standing upright, or picking up objects on the floor.

Femoral-on-pelvic hip osteokinematics – rotation of the femur about a relatively fixed pelvis.

Pelvic-on-femoral hip osteokinematics – rotation of the pelvis, and often the superimposed trunk, over relatively fixed femurs.

Movements: flexion & extension in the sagittal plane, abduction &

adduction in the frontal plane, and internal and external rotation in the horizontal plane.

The anatomic position is the 0-degree or neutral reference point. 44

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FEMORAL-ON-PELVIC OSTEOKINEMATICS Rotation of the Femur in the Sagittal Plane

Hip flexion to 120 degrees Full knee extension limits hip flexion to 70 – 80 degrees due to

increased tension in the hamstrings Hip extension to 20 degrees

Full knee flexion reduces hip extension due to tension in rectus femoris

Rotation of the Femur in the Frontal Plane Hip abduction to 40 degrees

Limited by pubofemoral ligament and adductors Hip adduction to 25 degrees

Limited by interference with contralateral limb, passive tension in hip abductors, iliotibial band, and ischiofemoral ligament

Rotation of the Femur in the Horizontal Plane Internal rotation to 35 degrees

Produces tension in piriformis and ischiofemoral ligament External rotation to 45 degrees

Produces tension in internal rotators and iliofemoral ligament

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SAGITTAL PLANE ROTATIONS

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FRONTAL PLANE ROTATIONS

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HORIZONTAL PLANE ROTATIONS

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FEMORAL-ON-PELVIC (HIP) MOTION

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PELVIC-ON-FEMORAL OSTEOKINEMATICS

Pelvic rotation in the Sagittal Plane Pelvic rotation in the Frontal Plane Pelvic Rotation in the Horizontal Plane

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LUMBOPELVIC RHYTHM The caudal end of the axial skeleton is firmly

attached to the pelvis by way of the sacroiliac joints.

Rotation of the pelvis over the femoral heads typically changes the configuration of the lumbar spine.

This is referred to as lumbopelvic rhythm. Ipsidirectional lumbopelvic rhythm.

The pelvis and lumbar spine rotate in the same direction.

Contradirectional lumbopelvic rhythm. The pelvis and lumbar spine rotate in opposite

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LUMBOPELVIC RHYTHMS

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PELVIC ROTATION IN THE SAGITTAL PLANE: ANTERIOR AND POSTERIOR PELVIC TILTING

Pelvic Tilt – a short-arc, sagittal rotation of the pelvis relative to stationary femurs.

Anterior Pelvic Tilt Increase in lumbar curvature offsets the

tendency of the supralumbar trunk to follow the forward rotation

30 degrees Posterior Pelvic Tilt

Decrease in lumbar curvature 15 degrees

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PELVIC ROTATION IN THE FRONTAL PLANE Pelvic-on-femoral rotation in the frontal and

horizontal planes is best described assuming a person is standing on one limb. The weight bearing extremity is referred to as the support hip.

Abduction of the support hip occurs by raising or “hiking” the iliac crest on the side of the nonsupport hip. The lumbar spine must bend in the direction opposite

the rotating pelvis. Slight lateral convexity within the lumbar region

toward the side of the abducting hip. 30 degrees of abduction

Adduction of the support hip occurs by a lowering of the iliac crest on the side of the nonsupport hip. Slight lateral concavity within the lumbar region of the

side of the adducted hip.

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PELVIC ROTATION IN THE HORIZONTAL PLANE

Pelvic-on-femoral rotation in the frontal and horizontal planes is best described assuming a person is standing on one limb. The weight bearing extremity is referred to as the support hip.

Internal rotation of the support hip occurs as the iliac crest on the side of the nonsupport hip rotates forward in the horizontal plane.

External rotation of the support hip occurs as the iliac crest on the side of the nonsupport hip rotates backward in the horizontal plane.

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PELVIC-ON-FEMORAL (HIP) MOTION

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ARTHROKINEMATICS

During hip motion, the nearly spherical femoral head normally remains snugly seated within the confines of the acetabulum.

Hip arthrokinematics are based upon traditional convex-on-concave or concave-on-convex principles.

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MOTOR INNERVATION Lumbar Plexus

Femoral nerve (L2-L4) Obturator nerve (L2-L4)

Sacral Plexus Nerve to piriformis (S1-S2) Nerve to obturator internus and gemullus

superior (L5-S2) Nerve to quadratus femoris and gemullus inferior

(L4-S1) Superior gluteal nerve (L4-S1) Inferior gluteal nerve (L5-S2) Sciatic nerve (L4-S3), including tibial and

common fibular (peroneal) portions 58

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SENSORY INNERVATION

As a general rule, the hip capsule, ligaments, and parts of the labrum receive sensory innervation through the same nerve roots that supply the overlying muscles.

The anterior part of the capsule of the hip receives sensory fibers from the femoral nerve.

The posterior capsule receives sensory fibers from all nerve roots originating from the sacral plexus.

The connective tissues of the medial aspects of the hip and knee joints receive sensory fibers from the obturator nerve (Inflammation of the hip may be perceived as pain in the medial knee region).

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OBTURATOR NERVE

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SCIATIC NERVE

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MUSCULAR FUNCTION AT THE HIP

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MUSCLES OF THE HIP, ORGANIZED ACCORDING TO PRIMARY OR SECONDARY ACTIONS

Flexors Adductors Internal Rotators

Extensors Abductors

External Rotators

Primary IliopsoasSartorius TFLRectus femorisAdductor longusPectineus

Pectineus Adductor longusGracilis Adductor brevisAdductor magnus

Not applicable

Gluteus maximusBiceps femoris (long head)SemitendinosusSemimembranosusAdductor magnus (posterior head)

Gluteus mediusGluteus minimusTFL

Gluteus maximusPiriformisObturator internusGemellus superiorGemellus inferiorQuadratus femoris

Secondary

Adductor brevisGracilisGluteus minimus (anterior fibers)

Biceps femoris (long head)Gluteus maximus (lower fibers)Quadratus femoris

Gluteus minimus (anterior fibers)Gluteus medius (anterior fibers)TFLAdductor longusAdductor brevisPectineus

Gluteus medius (posterior fibers)Adductor magnus (anterior head)

PiriformisSartorius

Gluteus medius (posterior fibers)Gluteus minimus (posterior fibers)Obturator externusSartoriusBiceps femoris (long head)

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MUSCLES OF THE ANTERIOR HIP

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HIP FLEXOR MUSCLES

The primary hip flexors are the iliopsoas, sartorius, tensor fascia latae, rectus femoris, adductor longus, and pectineus.

Secondary hip flexors are adductor brevis, gracilis, and anterior fibers of the gluteus minimus.

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PELVIC-ON-FEMORAL HIP FLEXION: ANTERIOR PELVIC TILT

The anterior pelvic tilt is performed by a force-couple between the hip flexor and low back extensor muscles.

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FORCE COUPLE FOR ANTERIOR PELVIC TILT

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FEMORAL-ON-PELVIC HIP FLEXION

Femoral-on-pelvic hip flexion often occurs simultaneously with knee flexion as a means to shorten the functional length of the lower extremity during the swing phase of walking or running.

Moderate to high power hip flexion requires coactivation of the hip flexor and abdominal muscles.

Rectus abdominus must create a strong posterior pelvic tilt to neutralize the strong anterior pelvic tilt potential of the hip flexors.

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STABILIZING ROLE OF ABDOMINALS WITH UNILATERAL LEG RAISING

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HIP ADDUCTOR MUSCLES

The primary adductors of the hip are the pectineus, adductor longus, gracilis, adductor brevis, and adductor magnus.

Secondary adductors are the biceps femoris (long head), the gluteus maximus (especially lower fibers) and the quadratus femoris.

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HIP ADDUCTORS

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BILATERAL COOPERATIVE ACTION OF ADDUCTORS

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DUAL ACTION OF ADDUCTOR LONGUS

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HIP INTERNAL ROTATORS: OVERALL FUNCTION

There are no primary internal rotators of the hip because no muscle is oriented close to the horizontal plane.

Secondary internal rotators are the anterior fibers of the gluteus minimus and gluteus medius, tensor fasciae latae, adductor longus, adductor brevis, and pectineus.

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HORIZONTAL PLANE LINES OF FORCE OF SEVERAL MUSCLES THAT CROSS THE HIP

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ADDUCTORS AS INTERNAL ROTATORS

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HIP EXTENSOR MUSCLES

The primary hip extensors are the gluteus maximus, the hamstrings (long head of the biceps femoris, semitendinosus, semimembranosus), and the posterior head of the adductor magnus.

Secondary extensors are the posterior fibers of the gluteus medius and the anterior fibers of the adductor magnus.

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POSTERIOR MUSCLES OF THE HIP

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PELVIC-ON-FEMORAL HIP EXTENSIONPERFORMING A POSTERIOR PELVIC TILT

Hip extensors performing a posterior pelvic tilt. The hip extensors and the abdominal muscles

act as a force couple to posteriorly tilt the pelvis. Hip extensors controlling a forward lean of

the body. The muscular support for this activity is primarily

the responsibility of the hamstrings.

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FORCE COUPLE FOR POSTERIOR PELVIC TILT

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HIP EXTENSORS CONTROLLING A FORWARD LEAN OF THE BODY

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FEMORAL-ON-PELVIC HIP EXTENSION

Hip extensor muscles are required to produce large and powerful femoral-on-pelvic hip extension torque to accelerate the body forward and upward (i.e. climbing a hill).

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HIP EXTENSOR ENGAGEMENT WHILE CLIMBING

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FULLY EXTENDABLE HIP

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EFFECTS OF HIP FLEXION CONTRACTURE ON THE BIOMECHANICS OF STANDING

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HIP ABDUCTOR MUSCLES

The primary hip abductor muscles are the gluteus medius, gluteus minimus, and tensor fasciae latae.

Secondary abductors are the piriformis and sartorius.

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DEEP MUSCLES OF POSTERIOR & LATERAL HIP

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ABDUCTOR CONTROL OF FRONTAL PLANE STABILITY OF THE PELVIS WHILE WALKING

The abduction torque produced by the hip abductor muscles is essential to the control of the frontal plane pelvic-on-femoral kinematics during walking.

The abduction torque produced by hip abductor muscles is particularly important during the single-limb-support phase of gait.

The abduction torque on the stance limb prevents the pelvis and trunk from dropping uncontrollably toward the side of the swinging limb.

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ABDUCTOR ROLE IN THE PRODUCTION OF COMPRESSION FORCE AT THE HIP

During single-limb support, the hip abductor muscles (esp. gluteus medius) produce most of the compression force across the hip.

The hip abductor muscles must produce a force that is twice that of body weight in order to achieve stability during single-limb support.

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GREATER TROCHANTERIC PAIN SYNDROME Excessive or repetitive action of the gluteus

medius and minimus can cause point tenderness adjacent to the greater trochanter (the primary distal attachment of these muscles).

This painful response suggests inflammation within the hip abductor mechanism.

Pain associated with activation of the hip abductor mechanism can be disabling considering the frequent and relatively large demands placed upon these muscles during the single-limb-support phase of the gait cycle.

Pain can be due to inflammation of the bursa associated with the distal attachments or with tears of the distal tendons.

The term greater trochanteric pain syndrome describes this condition. 90

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HIP ABDUCTOR MUSCLE WEAKNESS

Several conditions are associated with weakness of the hip abductor muscles. Muscular dystrophy, Guillian-Barre syndrome,

spinal cord injury, greater trochanteric pain syndrome, hip osteoarthritis or rheumatoid arthritis, poliomyelitis, and undefined hip pain or weakness.

The classic indicator of hip abductor weakness is the positive Trendelenburg sign. The patient is asked to stand in single-limb

support over the weak hip. A positive sign occurs if the pelvis drops to the

side of the unsupported limb. The weak hip “falls” into pelvic-on-femoral adduction.

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HIP EXTERNAL ROTATOR MUSCLES

The primary external rotator muscles of the hip are the gluteus maximus and five of the six “short external rotators”.

Secondary external rotators are the posterior fibers of gluteus medius and minimus, obturator externus, sartorius, and long head of biceps femoris.

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OBTURATOR INTERNUS

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FUNCTIONAL ANATOMY OF THE “SHORT EXTERNAL ROTATORS”

The six “short external rotators” of the hip are the piriformis, obturator internus, gemellus superior, gemellus inferior, quadratus femoris, and obturator externus.

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EXTERNAL ROTATORS OVERALL FUNCTION

The functional potential of the external rotators is most evident during pelvic-on-femoral rotation.

The action of planting a foot and “cutting” to the opposite side is the natural way to abruptly change direction while running.

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EXTERNAL ROTATOR ACTION

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FRACTURE OF THE HIP Fracture of the hip (i.e. proximal femur) is a major

health and economic problem in the United States. About 95% of all fractures of the hip are the result of

falls. It is the 2nd leading cause of hospitalization in the

elderly. Age related osteoporosis and a higher incidence of

falling are reasons for a higher incidence of hip fracture in the elderly.

Mortality is surprisingly high after hip fracture: studies report 12% to 25% of persons die within 1 year of fracturing a hip.

Only about 40% of persons are able to independently perform their basic functional activities 6 to 12 months after hip fracture.

About half of those persons continue to require an assistive device to aid their walking.

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OSTEOARTHRITIS OF THE HIP

Hip osteoarthritis is a disease manifested by deterioration of the joint’s articular cartilage, loss of joint space, sclerosis of subchondral bone, and the presence of osteophytes.

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EFFECTS OF COXA VARA & COXA VALGA

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