Hip & Pelvic Complex

Objectives of Studying the Sacroiliac Joint & Pelvic Complex

• Describe the function and articular features of the hip/pelvis
• Define the SI joint's motion and its relation to lumbopelvic movements
• Discuss stability factors of the SI joint
• Describe the pelvic region's passive stabilizing structures
• Identify the normal anatomic alignment of the hip and discuss alteration effects
• Describe the hip's osteokinematic & arthrokinematic motions
• Describe muscle activity and function concerning the hip

Pelvic Ring Composition and Function

• The pelvic ring consists of the sacrum and innominates.
• It includes the SI joints and pubic symphysis.
• It transfers body weight bidirectionally between trunk and femurs.

Pubic Symphysis Details

• The pubic symphysis is a cartilaginous joint.
• It is located between the two ends of the pubic bones.
• A fibrocartilaginous disc connects the pubic bones.

Sacrum Facts

• The sacrum is formed by five fused vertebrae, creating a wedge shape.
• S1 is the base of the sacrum.
• Two facets on S1 face posteriorly, articulating with the L5 inferior facets.
• S5 is the apex of the sacrum.
• The sacrum articulates with the coccyx.

Anatomy of the Sacroiliac Joint

• The SI joint spans from S1 to S3.
• It is partly synovial and partly syndesmosis (fibrous).
• The synovial portion has an "L" shape and may be "C" shaped or auricular.
• Ilial tuberosities articulate with sacral tuberosities through SI interosseous ligaments, forming the fibrous part of the joint.
• Size, shape, and roughness of joint surfaces can vary greatly between individuals.
• Irregular shapes help the joint "lock in" to place.

Sacroiliac Joint Characteristics

• Younger individuals have greater SI joint mobility.
• In childhood, the joint is relatively mobile with smooth, flat surfaces.
• Joint surfaces roughen between puberty and adulthood, forming grooves and depressions.
• The capsule becomes more fibrotic and less pliable with age.

Function of the SI Joint

• Provides stability for load transfer between the axial skeleton and lower limbs
• Provides stress relief to the pelvic ring
• Designed for stability through ligamentous support and irregular articular surfaces
• Movement
  • Very minimal, but includes gliding/translation of ~1 - 2 mm,
  • Rotation of ~2-4°
  • motion decreases as we age
• No muscles directly act at the SI joint
• Movement occurs secondary to motion at adjacent joints

Understanding Pelvic Motions

• Anterior Tilting: ASISs move inferiorly, PSISs move superiorly, creating relative hip flexion, and increasing lumbar lordosis.
• Posterior Tilting: PSISs move inferiorly, ASISs move superiorly, creating relative hip extension, and flattening lumbar lordosis.

SI Joint Motions: Nutation and Counternutation

• Nutation: The base of the sacrum tilts anteriorly relative to the ilium and is also known as sacral locking.
  • It is the most stable position of the SI joint -It involves forward motion of the sacral base into the pelvis or backward rotation of the ilium on the sacrum.
  • Nutation occurs with posterior pelvic tilt, causing the ilia to move closer together and the ischial tuberosities to move farther apart.
• Counternutation: The base of the sacrum tilts posteriorly relative to the ilium and is also known as sacral unlocking. -It's the opposite movement to nutation.
  • Counternutation involves posterior motion of the sacral base out of the pelvis
  • Occurs with anterior pelvic tilt, causing the iliac bones to move farther apart and the ischial tuberosities to move closer together.
• Occurs via motion of the sacrum on the ilium, the ilium on the sacrum, or simultaneous motion of both.

Key Sacroiliac Ligaments

• Iliolumbar Ligament: Stabilizes the lumbosacral joint reinforcing its anterior aspect.
• Interosseous Ligament: Strongest SI joint ligament that rigidly binds the sacrum and ilium.
• Anterior Sacroiliac Ligaments: Relatively thin ligaments compared to the others limit nutation.
• Long Posterior Sacroiliac Ligament: Limits pelvic rotation or Sacral counternutation
• Short Posterior Sacroiliac Ligament: Limits all pelvic and sacral movements
• Sacrotuberous and Sacrospinous Ligaments: Limits nutation and posterior innominate rotation and provide vertical stability, particularly resisting superior translation of the sacrum

Stress Relief in the Pelvic Ring

• Motion at the SI joints and pubic symphysis helps dissipate stress
• Reciprocal motions during walking, running, exercise is important
• Pelvis rotations are out of phase on each side in walking
• Tension in muscles & ligaments creates oppositely directed torsions through right & left iliac crests
• Intrapelvic torsions increase with walking speed

Pelvic and Sacral Movements with Lumbar Motion

• Flexion of the lumbar spine is associated with anterior tilt of the innominate and counternutation of the sacrum.
• Extension of the lumbar spine is associated with posterior tilt of the innominate and nutation of the sacrum.
• Rotation: Ipsilateral Side: Posterior tilt, Contralateral Side: Anterior Tilt- Ipsilateral Side: nutation, Contralateral Side: counternutation
• Side-bending: Ipsilateral Side: Anterior Tilt, Contralateral Side: Posterior Tilt- Ipsilateral Side:, Contralateral Side: nutation counternutation

Understanding Lumbopelvic Rhythm

• Full trunk motion involves a combination of movements from the lumbar spine, pelvis, and hip.
• The ratio of contribution from these areas is called lumbopelvic rhythm.
• The motions occur simultaneously in healthy individuals.
• If hip flexion is limited, greater flexion of the lower thoracic and lumbar regions is needed.
• If lumbar mobility is restricted, greater hip flexion is needed to compensate.

Lumbopelvic Rhythm during Extension

• Initial trunk extension - Hip extension, via activation of hip extensors (glut max & hamstrings)
• Middle Trunk phase - Trunk extension occurs via shared activation of hip & lumbar extensors
• After LOG shifts posterior to hips - Muscle activity decreases

Factors Affecting SI Joint Stability

• Form Closure:
  • Refers to the closed-packed position of the joint and nutation of the sacrum. - Joint shape, friction, and ligamentous integrity impact form closure.
• Force Closure: - Extrinsic factors impacting stability where it highly relies on muscle action. - Greater muscle activation is required to maintain stability as counternutation occurs.
• Motor Control: - It is related to the timing and coordination of muscles.

Hip Joint Overview

• The hip joint, or coxofemoral joint is a diarthrodial, triaxial joint.
• Acetabulum is the concave socket that makes up the proximal articular surface.
• A convex femoral head is a distal articular surface on the hip joint.
• The coxofemoral joint supports weight of the HAT (head, arms, trunk)

Hip Joint Anatomy

• It is formed from 3 bones that contribute to the actabulum: ilium, ischium, and pubis.
• Full ossification of the pelvis occurs between the ages of 20-25 years.

Acetabulum

• Hyaline cartilage covers periphery of the acetabulum (lunate surface).
• The area articulating with the femoral head on the acetabulum has a horseshoe shape to it.
• The acetabulum is deepened by the fibrocartilaginous labrum.
• The acetabular fossa is a non-articular area containing fibro-elastic fat covered with a synovial membrane.
• Laterally positioned with an inferior and anterior tilt with only the upper margin is a circular contour
• Blood vessels pass pass through fibro-osseous tunnel into acetabular fossa

Center Edge Angle

• It is the angle of Wiberg and measures acetabular depth
• Indicates how much of the femoral head covered by the acetabulum.
• It is formed by 2 lines originating at the center of the femoral head - One line extends vertically - Another line extends to the lateral aspect of the acetabulum
• Classified as normal between 25 - 40° and definite dysplasia is defined as < 16°.
• Excessive Acetabular coverage would be >40°

Acetabular Labrum Function

• Labrum: A wedge shaped fibrocartilage covering the acetabulum - Deepens socket & increases concavity - Grasps the femoral head to maintain contact with acetabulum - Acts as a seal to maintain negative intra-articular pressure - Decreases the force transmitted to articular cartilage
  • Nerve endings are located w/in labrum

Femoral Head

• Has a fairly rounded hyaline cartilage-covered surface with an articulation area forming ~ 2/3 of a sphere
• It is more circular than the acetabulum and has a small pit/Fovea that is not covered in articular cartilage - Serves as attachment site for the ligamentum teres
• The femoral neck is ~ 5 cm long and it is also angled with the head facing medially, superiorly, and anteriorly in relation to the femoral shaft and distal condyles
• Angle of inclination. - Frontal plane angle made through the femoral neck of the longitudinal shaft - Normal angles are ~125° in adults with slight variation bilaterally - Normal range: 120 to 135 degrees - Tends to be smaller angles in females - Larger angles in taller individuals Gradually declines to ~125° with skeletal maturity and changes across the lifespan

Deviations Impacting The Femoral Head

• Coxa Valga: Pathologically >125° - More contact with acetabulum with decreased joint stability - Femoral head rests deeper in hip - Vertical WBing line shifts closer to the shaft requiring more abductor force to counterbalance adduction and greater muscular force can mean greater total force
• Coxa Vara: Pathologically<125° and the femoral head rests deeper in hips - If note caused by trauma muscle is activated or abductors are used and the force needed by abductors in stance lowers, with high bending moment - ↑Density in trabeculae laterally and leads to greater tensile stress

Angle of Torsion

• It is a transverse plane angle with the longitudinal axis of femoral head and neck to another through the distal femoral condyles
• Head & neck are offset anteriorly with respect to condyles with an average range 10° - 20° in those who are mature
• Angle decreases with age and newborns are at 30°-40°
• Excessive Anteversion occurs when the angle > 15° to 20° - Associated with increased IR ROM at hip and decreased ER ROM
• Retroversion occurs when the angle < 15° to 20° - Associated with increased ER ROM at hip and decreased and IR ROMs at hip.
• Can predispose to labral tears or degenerative joint disease

Compensations Related to Femoral Torsion

• Excessive anteversion presents in toe gait and assists with articulating.
• Inversion presents with "out toe" and works to improve articular contact.

Negative Pressure

• Critical for maintaining joint congruence
• Hip is broken and must be pressured w/in order to get dislocated
• Labrum acts as the seal to preserve the negative pressure - The "seal" has tears

Joint Capsule Details

• It is a major source or support for stability and is thick anterior and posterior with a lax
• Serves as a collar structure to secure the femoral neck
• Site to secure attachment to oblique fibers and and provides assistance to secure from separation from the acetabulum
• Supports 2/3 of body weight on hip

Ligaments of The Hip

• Iliofemoral (”Y” Ligament) - Proximal attachment at AIIS and iliac acetabulum. - Distally thick anterior area where jt caps are attached at area with intertrochanter line in femur. Motion impacted is hyperextension and to a degree some ER as well as Posterior pelvic tilt. Upper portion helps adduction
• Pubofemoral - Proximal: in pubis in the front or inside of acetabulum
  • Distally: attached at front and inside anterior where the line near the femur is near intertrochanter and also at back-side of the femur.. Motion impacted is hip extension,abduction,ER

Ischiofemoral Ligament of The Hip Joint;

• Proximally: ischial region of the rim w/ labrum in the rear + lower part, attached at end and near Femur; Impacted Motions: IR and Hyperextension, also great when flexing, while upper part limits range and assists extreme adduction ( esp at flex).
• • Ligamentum teres secures at the center around area w/ the acetabular fossa including femoral head where role serves are as channel for the branch w/ the obturator artery (main blood line) for hip and supports action when combines/combines and in those with extension +IR/. Blood to Femoral Head:
  • Depends on the role as a blood aspect as related is more for duration with development. Arteries are retinaculum not able to use growth areas, need source given by ligamenrum as vessels sclerosed for the elderly with bad supply/ primary. Cause: femoral neck have have more cases. Open area:
    • Range with more space or with abduct while slightly ER Close:
    • Is extreme extension that has slight abduct and inside, and ligaments twist near and on region where can create separations and must hold from area with capsule

Hip- Motion Facts

• Motion occurs 10-30 degrees with flex with abduct near slightly ER during standing or the close area during extensions that twist region at femur to avoid separations
• Neutral Position, - Cartilage showing is support high on top

Hip Structure Related To Adaptations;

.Trabeculae help align while in more stress on top area

• Pass through SI points with acetabular System structure provides support
• 2 parts traberc: Medial =compressive/ near middle Side= pulling/ lateral - At areas where is most strength, parts near points work better vs spots not in range .

External Force Impact The Hip

1. Impact due to force, HAT has the weight with at last 1/ or higher thru head as with bending when head move,
2. High effect on with greater bending.
3. Stuct systems help to resist on structures from force and direction on either shaft or surface. Area: medially, vs laterally tensile, while front or pulling that creates on structures
4. The force with support at HAT is from ground to direction

Weights and How Apply

a. From ground reaction are to move leg to create force, has bending effect from region. Plane force occurs medial for force to tensile.

HIPROM With Axis Facts

Axis of Motions: Has 125 with motion range as Flex, Extend, while with rotations to rotate

Understanding hip, pelvis and motion

• Hip in a Pelvis: (Flex or Extend/ with adduc)., turns on either section . Area can turn to front then back on same side at flex Pelvis to Hip: Has tilt + turns for it, In relation to joints turning over that changes over joint

Arthrokinematics

• Flexion - Head slides posterior
• Extension- Head slides minor anterior
• Abduction- Head roll on one end vs slide inferior
• IR/ER : Head flex 1st then glide with turn

HIP Muscles

• Region to function. , location for position Has two actions such: and (inside with outside turning) Function also: with support and function

Hip Primary Flexors

-Iliopsoas - and Rectus are to allow pull from seat 90deg that joins support from parts with vertebra / the head as one.

• Pectineus/ Tensor - . With 2 supports it flex and pull in area or has some use in flexing with flex A major primary muscles for this location!

Tensor/Sartorius Impact

. Helps bend, assist to side to also rotate it all.

• Tension has support to stand vs stress when bending

Important Extensors As Related To The Area

• Glut: has support mainly or high resist from strength. Peak comes 70 flexion with ability ER

Hamstring

1. Helps hold joint and also has bending with resist 2 MA on area from supports is smaller then support area 3: Joint and Flexed at 90, then this with with to add better

Support And Muscles Function

1 For flexion the ER is high for anterior pelvis that is close, while with muscle action abdominal can push or pull in rear.

Impact of HIPabductor Muscles (Glut & Mini)

• Has small area of effect to assist and hold legs, but stronger and has offset for forces to pull to joints. This pull can effect in relation to area of limb. .

Hip With Side: abductor or added pull

• Side impact and function of side

Hip Adductor Muscles vs Glut/ Mini)

. Can support leg in all to rotate to middle and not.

Role For Rotator At Exterior Leg;

• Rotations is needed internally and Extern. Main ER in the area:

Region Action Vs Support With Rotator Exterior

" It gives support and help with bending or help hold joints or give needed stability or better force + position