CH.9 Joints & Articulations

Ch 9 : Joints & Articulations

Learning Objectives

• Discuss functional and structural classifications for body joints.
• Describe the characteristic features for fibrous, cartilaginous, and synovial joints and give examples of each.
• Define and identify the different body movements.
• Discuss the structure of specific body joints and the movements allowed by each.
• Explain the development of body joints.

Planes and Axes of Motion

• Uniaxial – motion in one plane.
• Biaxial – motion in two planes.
• Multiaxial – motion in more than two planes.

What is a Joint?

• Joints allow mobility within our skeleton.
• Each joint reflects a compromise between the need for strength and the need for mobility. As a result, articulations differ in the amount of movement permitted, and this property is known as range of motion (ROM).
• The anatomical structure of a joint determines the type and amount of movement that may occur.
• A joint is a point of contact between:
  • Two or more bones
  • Cartilage and bone
  • Teeth and bone

Classification of Joints

• Joints can be classified:
  • Structurally
    • Is there a joint cavity?
    • What type of connective tissue is involved?
  • Functionally
    • What degree of movement is permitted?

Structural Classification of Joints

• Fibrous – no articular cavity
  • Articulating bones held together by dense irregular connective tissue
  • Types: Sutures and Syndesmoses
• Cartilaginous – no articular cavity
  • Articulating bones held together by hyaline cartilage (Synchondrosis) or fibrous cartilage (Symphysis)
• Synovial – have articular capsule
  • Characterized by synovial cavity and articular cartilage; may contain accessory ligaments, articular discs, and bursae

Structural Classification

• Fibrous joints (synarthroses): adjacent bones are joined by collagen fibers. 3 kinds:
  • sutures, gomphoses and syndesmoses.
• Cartilaginous joints (amphiarthroses): two bones are joined by cartilage. 2 kinds:
  • synchondroses, and symphyses.
• Synovial joints (Diarthroses): freely movable and most common joint in the body.

Functional Classification

• Synarthroses – joints that have NO movement.
  • Eg: sutures of the skull, gomphoses- teeth
• Amphiarthroses – partially movable joints.
  • Eg: intervertebral disc and pubic symphysis
• Diarthroses – freely movable joints.
  • The most common type of functional joint in the body.
  • Eg: knee joint, shoulder joint, finger joints, ankle and wrist joints, etc.

Examples of Joints

• Fibrous:
  • Sutures (skull)
  • Gomphoses (teeth)
  • Syndesmosis: Interosseous ligament e.g. radius/ulna
• Cartilaginous:
  • Primary - Synchondroses e.g. sternocostal/ costal cartilages
  • Secondary – Symphyses (with pad of fibrocartilage) e.g. pubic symphysis, IV joint
• Synovial:
  • Uniaxial
    • Hinge e.g. elbow
    • Pivot e.g. radio-ulna joint
    • Gliding (plane) e.g. intercarpal bones
  • Biaxial
    • Saddle e.g. 1st Carpometacarpal joint
    • Condyloid e.g. Metacarpal phalangeal joints
    • Ellipsoid e.g. radiocarpal joint
  • Multiaxial
    • Ball & Socket e.g. hip

Skeletal System

• The skeletal systems is composed of different types of connective tissues:
  • Bones – rigid structure
  • Cartilage – soft, cushions the joints
  • Ligaments – attach bone to bone
  • Tendons – attach muscle to bone.
  • Tendons link the skeletal and the muscular systems

Cartilage

• Cartilage - flexible connective tissue not as strong as bone tissue.
  • Function: Cushion joints, flexible
  • Found at the ends of long bones, nose, ends of ribs, larynx and trachea, disks between vertebrae and knee, ear flaps and epiglottis.
  • Cartilage cells are chondrocytes
  • Cartilage lacks blood vessels, so slow to heal

Tendons and Ligaments

• Ligaments – connective tissue that connects bone to bone
• Tendons – connective tissue that connects muscle to bone

Comparison of Joint Mobility

• Fibrous Joints
  • Lack a synovial cavity
  • Articulating bones are held together with dense fibrous connective tissue
  • Permit little or no movement
  • Types:
    • Sutures
    • Syndesmoses

Structural and Functional Classification of Fibrous Joints

• Fibrous: No Articular Cavity; Articulating Bones Held Together by Dense Irregular Connective Tissue.
  • Suture: Articulating bones united by thin layer of dense irregular connective tissue, found between skull bones; with age, some sutures replaced by synostosis (separate cranial cavity bones fuse into single structure
    • Degree of Movement: Immovable and slightly movable.
    • Example: Coronal suture.
  • Syndesmosis: Articulating bones united by a varying amount of dense irregular connective tissue, usually a ligament or membrane.
    • Degree of Movement: Slightly movable.
    • Example: Distal tibiofibular joint and interosseous membrane between tibia and fibula (anterior tibiofibular ligament).

Cartilaginous Joints

• Lack a synovial cavity
• Articulating bones are held together with cartilage connective tissue
• Permit little or no movement
• Types of cartilaginous joints:
  • Synchondroses: is a cartilaginous joint where bones are joined together by hyaline cartilage, or where bone is united to hyaline cartilage
  • Symphyses: a place where two bones are closely joined, either forming an immovable joint (as between the pubic bones in the center of the pelvis) or completely fused (as at the midline of the lower jaw).

Structural and Functional Classification of Cartilaginous Joints

• Cartilaginous: No Articular Cavity; Articulating Bones United by Hyaline Cartilage or Fibrous Cartilage.
  • Synchondrosis: Connecting material: hyaline cartilage.
    • Degree of Movement: Slightly movable to immovable.
    • Example: Between first rib and manubrium of sternum. Epiphyseal cartilage between diaphysis and epiphysis of long bone.
  • Symphysis: Connecting material: broad, flat disc of fibrous cartilage.
    • Degree of Movement: Slightly movable to immovable.
    • Example: Pubic symphysis and intervertebral joints.

Types of Synovial Joints

• Plane (gliding) Joints
• Hinge Joints
• Pivot Joints
• Condyloid Joints
• Saddle Joints
• Ball and Socket Joints

Synovial Joints (diarthroses)

• Have a synovial cavity
• Articulating bones are covered with articular cartilage, held together by ligaments, contain synovial fluid
• The ends of bones are encased in smooth cartilage.
• They are protected by a joint capsule lined with a synovial membrane that produces synovial fluid.
• The capsule and fluid protect the cartilage, muscles, and connective tissues.
• Have a nerve and blood supply, and are surrounded by an articular capsule
• Permit a large range of movement
• Eg : knee joint, elbow joint, shoulder and hip joints and the phalanges of hands and feet, etc.
• Freely movable joints held together by ligaments.
• Synovial membrane - produces synovial fluid, an excellent lubricant for the joints. This fluid is largely derived from blood and has a clear, viscous, egg-white consistency. Its function is to provide lubrication, nutrient distribution and shock absorption.
• Menisci – a pad of fibrous cartilage situated between opposing bones within a synovial joint
• Cartilage: The articular cartilages provide a slick, smooth surface to the bones which reduces friction during movement.

Accessory Joint Structures

• Ligaments: support, strengthen, and reinforce synovial joints
• Fatty pads: localized masses of adipose tissue covered by a layer of synovial membrane
• Meniscus: a pad of fibrous cartilage situated between opposing bones within a synovial joint.
• Bursae - a small, fluid-filled pocket that forms in a connective tissue. It contains synovial fluid and is lined by a synovial membrane.
• Tendon sheaths -fibrous tissue connecting a muscle to a bone

Structure of a Synovial Joint

• Structures in a Synovial Joint
  • Articular capsule – external and internal
  • Joint/synovial cavity – filled with synovial fluid
  • Articular cartilage – Hyaline cartilage
  • Synovial fluid – viscous/ clear colorless fluid
  • Ligaments – give the joint reinforcement and strength
  • Nerves – provide feelings of pain and stretch
  • Vessels - provide nutrients to joint

Structural and Functional Classification of Synovial Joints

• Synovial: Characterized by Synovial Cavity, Articular Cartilage, and Articular (Joint) Capsule; May Contain Accessory Ligaments, Articular Discs, and Bursae.
  • Plane: Articulated surfaces flat or slightly curved. Many are biaxial: back-and-forth and side-to-side movements. Some are triaxial: back- and-forth, side-to- side, rotation.
    • Example: Intercarpal, intertarsal, sternocostal (between sternum and second to seventh pairs of ribs), and vertebrocostal joints.
  • Hinge: Convex surface fits into concave surface. Uniaxial: flexion-extension.
    • Example: Elbow, ankle, and interphalangeal joints.
  • Pivot: Rounded or pointed surface fits into ring formed partly by bone and partly by ligament. Uniaxial: rotation.
    • Example: Atlanto-axial and radioulnar joints.
  • Ellipsoid: Oval-shaped projection fits into oval-shaped depression. Biaxial: flexion-extension, abduction-adduction.
    • Example: Radiocarpal and metacarpophalangeal joints.
  • Saddle: Articular surface of one bone is saddle-shaped; articular surface of other bone "sits" in saddle. Biaxial: flexion-extension, abduction-adduction.
    • Example: Carpometacarpal joint between trapezium and metacarpal of thumb.
  • Ball-and-socket: Ball-like surface fits into cuplike depression. Triaxial: flexion-extension, abduction-adduction, rotation.
    • Example: Glenohumeral and hip joints.

Movements Allowed by Synovial Joints

• Gliding: bony surfaces of bone slide or glide over each other
• Flexion: bending movement that decreases the angle
• Extension: movement the increases the angle, opposite of flexion
• Abduction: moving away from longitudinal axis
• Adduction: movement toward the longitudinal axis
• Circumduction : movement of the limb such that it describes a cone
• Rotation : turning the bone or limb around its long axis
• Supination – rotating the forearm laterally such that the palm faces superiorly
• Pronation: rotating the forearm medially such that the palm faces inferiorly
• Inversion : sole of the foot faces or turns medially
• Eversion : sole of the foot turn laterally
• Protraction: jutting out of the jaw
• Retraction : moving the jaw backward
• Elevation : lifting the limb or body superiorly
• Depression: moving the body part inferiorly
• Opposition : to bring the thumb and index finger tips together

Typical Synovial Joint - Knee Joint

Knee joint structures:

• Articular capsule
• Synovial membrane
• Medial and lateral menisci
• Supra patellar, infra patellar and pre patellar bursae
• Anterior and posterior cruciate ligaments
• Tibial and fibular collateral ligaments
• Patellar capsule
• Articular cartilage
• Tendon of quadriceps femoris

Additional joint structures:

• Ligaments- join bones to bones, consists of dense regular connective tissue.
• Tendons- join muscles to bone, consists of dense regular connective tissue.
• Tendon sheaths – a tube-like bursae that wraps around tendons subject to a great deal of friction
• Bursae- fibrous sac lined with synovial membrane and containing synovial fluid
• Occurs between bones and tendons or muscles
• Acts to decrease friction during movement

Knee Joint - Anatomical Components

• Articular capsule
• Medial and Lateral patellar retinacula, Patellotibial ligament, Oblique popliteal ligament, Arcuate popliteal ligament, Tibial collateral ligament, Fibular collateral ligament, intracapsular ligaments (ACL and PCL), Articular discs, Bursae

Movements:

• flexion, extension, slight medial and lateral rotation

Types of Synovial Joints

• Pivot Joints
  • Rounded end of one bone protrudes into a sleeve or ring composed of bone or ligament
  • Uniaxial
  • Eg: the joint between the dens of the axis to the atlas. Also proximal radioulnar joint
• Hinge Joints
  • Cylindrical projection of one bone fits into a trough-shaped surface on another bone
  • Uniaxial
  • Examples: elbow joint, knee joint, ankle joint, and interphalangeal joints
• Condyloid Joints
  • Also known as ellipsoid joint
  • Oval articular surface of one bone fits into a complementary depression in another
  • Biaxial
  • Eg: radiocarpal joints, metacarpophalangeal joint
• Saddle Joints
  • Articular surfaces have a concave area on one that fits with the convex area of the other
  • Biaxial
  • Examples: the 1st carpo-metacarpal joint and sterno-clavicular joint
• Plane Joints
  • Also known as gliding joints
  • Articular surfaces are flat and only allow for short gliding movements
  • Multi-axial
  • Eg: intercarpal and intertarsal joints, acromioclavicular joint, and zygapophysial joint
• Ball-in-Socket Joints
  • The spherical end of one bone articulates with a cuplike socket of another bone
  • Multi-axial
  • Example: shoulder and hip joints

Types of Movement at Synovial Joints

• Movement
  • Gliding: Movement of relatively flat bone surface back-and-forth and side-to- side over another; little change in angle between bones.
  • Angular: Increase or decrease in angle between bones.
  • Flexion: Decrease in angle between articulating bones, usually in sagittal plane or an anterior movement at a ball-and-socket joint.
  • Lateral flexion: Movement of trunk in frontal plane.
  • Extension: Increase in angle between articulating bones, usually in sagittal plane or a posterior movement at a ball-and-socket joint.
  • Abduction: Movement of bone away from midline, usually in coronal plane.
  • Adduction: Movement of bone toward midline, usually in coronal plane.
  • Circumduction: Flexion, abduction, extension, adduction, and rotation in succession (or in the opposite order); distal end of body part moves in circle.
  • Rotation: Movement of bone around longitudinal axis; in limbs, may be medial (toward midline) or lateral (away from mid line).
  • Special: Occurs at specific joints.
    • Inversion: Medial movement of sole.
    • Eversion: Lateral movement of sole.
    • Dorsiflexion: Bending foot in direction of dorsum (superior surface).
    • Plantar flexion: Bending foot in direction of plantar surface (sole).
    • Supination: Movement of forearm that turns palm anteriorly.
    • Pronation: Movement of forearm that turns palm posteriorly.
    • Opposition: Movement of thumb across palm to touch fingertips on same hand.
    • Elevation: Superior movement of body part.
    • Depression: Inferior movement of body part.
    • Protraction: Anterior movement of body part in transverse plane.
    • Retraction: Posterior movement of body part in transverse plane.

Factors Affecting Contact and Range of Motion at Synovial Joints

• Structure and shape of the articulating bones
• Strength and tension of the joint ligaments
• Arrangement and tension of the muscles
• Contact of soft parts
• Hormones
• Disuse

Selected Joints of the Body

• Axial Skeleton Joints
  • Suture: Between skull bones. Fibrous. None.
  • Atlanto-occipital: Between superior articular facets of atlas and occipital condyles of occipital bone. Synovial (ellipsoid). Flexion and extension of head; slight lateral flexion of head to either side.
  • Atlanto-axial: (1) Between dens of axis and anterior arch of atlas; (2) between lateral masses of atlas and axis. Synovial (pivot) between dens and anterior arch; synovial (planar) between lateral masses. Rotation of head.
  • Intervertebral: (1) Between vertebral bodies; (2) between vertebral arches. Cartilaginous (symphysis) between vertebral bodies; synovial (planar) between vertebral arches. Flexion, extension, lateral flexion, and rotation of vertebral column.
  • Vertebrocostal: (1) Between articular facets of heads of ribs and costal facets of bodies of adjacent thoracic vertebrae and intervertebral discs between them; (2) between articular facet of tubercles of ribs and transverse costal facet of thoracic. Synovial (planar). Slight gliding.
  • Sternocostal: Between sternum and first seven pairs of ribs. Cartilaginous (synchondrosis) between sternum and first pair of ribs; synovial (plane) between sternum and second through seventh pairs of ribs. None between sternum and first pair of ribs; slight gliding between sternum and second through seventh pairs of ribs.
  • Lumbosacral: (1) Between body of fifth lumbar vertebra and base of sacrum; (2) between inferior articular facets of fifth lumbar vertebra and superior articular facets of first vertebra of sacrum. Cartilaginous (symphysis) between body and base; synovial (planar) between articular facets. Flexion, extension, lateral flexion, and rotation of vertebral column.
• Appendicular Skeleton Joints
  • Sternoclavicular: Between sternal end of clavicle, manubrium of sternum, and first costal cartilage. Synovial (plane, pivot). Gliding, with limited movements in nearly every direction.
  • Acromioclavicular: Between acromion of scapula and acromial end of clavicle. Synovial (plane). Gliding and rotation of scapula on clavicle.
  • Radioulnar: Proximal radioulnar joint between head of radius and radial notch of ulna; distal radioulnar joint between ulnar notch of radius and head of ulna. Synovial (pivot). Rotation of forearm.
  • Wrist (radiocarpal): Between distal end of radius and scaphoid, lunate, and triquetrum of carpus. Synovial (ellipsoid). Flexion, extension, abduction, adduction, circumduction, and slight hyperextension of wrist.
  • Intercarpal: Between proximal row of carpal bones, distal row of carpal bones, and between both rows of carpal bones (midcarpal joints). Synovial (plane), except for hamate, scaphoid, and lunate (midcarpal) joint, which is synovial (saddle). Gliding plus flexion, extension, abduction, adduction, and slight rotation at midcarpal joints.
  • Carpometacarpal: Carpometacarpal joint of thumb between trapezium of carpus and first metacarpal; carpometacarpal joints of remaining digits formed between carpus and second through fifth metacarpals. Synovial (saddle) at thumb; synovial (plane) at remaining digits. Flexion, extension, abduction, adduction, and circumduction at thumb; gliding at remaining digits.
  • Metacarpophalangeal and metatarsophalangeal: Between heads of metacarpals (or metatarsals) and bases of proximal phalanges. Synovial (ellipsoid). Flexion, extension, abduction, adduction, and circumduction of phalanges.
  • Interphalangeal: Between heads of phalanges and bases of more distal phalanges. Synovial (hinge). Flexion and extension of phalanges.
  • Sacroiliac: Between auricular surfaces of sacrum and ilia of hip bones. Synovial (plane). Slight gliding (even more so during pregnancy).
  • Pubic symphysis: Between anterior surfaces of hip bones. Cartilaginous (symphysis). Slight movements (even more so during pregnancy).
  • Tibiofibular: Proximal tibiofibular joint between lateral condyle of tibia and head of fibula; distal tibiofibular joint between distal end of fibula and fibular notch of tibia. Synovial (plane) at proximal joint; fibrous (syndesmosis) at distal joint. Slight gliding at proximal joint; slight rotation of fibula during dorsiflexion of foot.
  • Ankle (talocrural): (1) Between distal end of tibia and its medial malleolus and talus; (2) between lateral malleolus of fibula and talus. Synovial (hinge). Dorsiflexion and plantar flexion of foot.
  • Intertarsal: Subtalar joint between talus and calcaneus of tarsus; talocalcaneonavicular joint between talus and calcaneus and navicular of tarsus; calcaneocuboid joint between calcaneus and cuboid of tarsus. Synovial (plane) at subtalar and calcaneocuboid joints; synovial (saddle) at talocalcaneonavicular joint. Inversion and eversion of foot.
  • Tarsometatarsal: Between three cuneiforms of tarsus and bases of five metatarsal bones. Synovial (plane). Slight gliding.
• Temporomandibular Joint
  • Anatomical Components
    • Articular capsule
    • Articular disc (meniscus), Lateral ligament, Sphenomandibular ligament, Stylomandibular ligament
  • Movements
    • Depression, elevation, protraction, retraction, lateral displacement, slight rotation
• Shoulder Joint
  • Anatomical Components
    • Articular capsule
    • Coracohumeral ligament, Glenohumeral ligaments, Transverse humeral ligament, Glenoid labrum, Bursae
  • Movements
    • flexion, extension, hyperextension, abduction, adduction, medial and lateral rotation, circumduction
• Glenohumeral Joint Injuries
  • Rotator cuff injury – occurs from wear and tear, aging, trauma, poor posture, improper lifting and repetitive movements
  • Dislocated shoulder – head of humerus becomes displaced from glenoid cavity; damages ligaments, tendons, muscles
  • Separated shoulder – partial or complete tearing of acromioclavicular ligament
• Elbow Joint
  • Anatomical Components
    • Articular capsule
    • Ulnar collateral ligament, Radial collateral ligament, Annular ligament of the radius
  • Movements
    • flexion and extension
  • Injuries
    • Tennis Elbow - pain at or near lateral epicondyle of humerus
    • Little League Elbow – inflammation of the medial epicondyle
    • Dislocation of radial head - most common upper limb dislocation in children. Head of radius slides past radial annular ligament
• Hip Joint
  • Anatomical Components
    • Articular capsule
    • Iliofemoral ligament, Pubofemoral ligament, Ischiofemoral ligament, Ligament of the head of the femur, Acetabular labrum, Transverse acetabular ligament
  • Movements
    • flexion, extension, abduction, adduction, medial and lateral rotation, circumduction

Aging and Joints

• As we age, our joints experience:
  • Decreased production of synovial fluid
  • Thinning of articular cartilage
  • Loss of ligament length and flexibility

Arthroplasty

• A surgical procedure to restore the function of a joint.
• A joint can be restored by resurfacing the bones.
• An artificial joint (called a prosthesis) may also be used. Various types of arthritis may affect the joints.
• Joint replacement surgery can be performed to counter some of the effects of aging