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Joints
Chapter 9
Joints
Joints/Articulations:
Point of contact between 2 or more bones.
Arthrology: study of joints and disorders.
Kinesiology: study on musculoskeletal movements.
Classification of Joints
A joint can have a very simple or a very complex
structure.
Tightly fitted joints  restricted movement.
Loosely fitted joints  greater movement….but also
prone dislocations.
Joints can be classified based on their:
Function….what type of movement they have?
Structure….what type of tissue joins the bones?
Functional Classification of Joints
Functional classification:
Joints can have a range of motion…from no
movement  freely movable joints.
Extent of movement depends on how the bones fit,
how muscle tendons attach, and how bone
ligaments attach.
Classification based on the degree of movement
allowed at the joint:
1. Synarthosis
2. Amphiarthrosis
3. Diarthrosis
Functional Classification of Joints - Synarthrosis
Synarthosis:
No movement at the joint.
Examples:
Joints of facial bones
Joints of cranial bones
Joint of ribs to the sternum
Teeth attachment to the jaws
Functional Classification of Joints - Amphiarthrosis
Amphiarthosis:
Some movement at the joint.
Examples:
Vertebral column
Tibia-fibula
Functional Classification of Joints - Diarthrosis
Diarthosis:
Freely movable joints.
Examples:
Shoulder
Elbow
Fingers
Hip
Knee
Toes
Structural Classification of Joints
Structural classification:
Joints vary in the type of tissue that joins
the bones, and presence or absence of
space between the bones.
Classification is based entirely on the
anatomy of the joints:
1. Fibrous joints
2. Bony joints
3. Cartilaginous joints
4. Synovial joints
Structural Classification of Joints - Fibrous
Fibrous joints:
- Bones are connected by different amounts of fibrous connective
tissue.
- Mostly immovable (synarthrosis)….some may be amphiarthrosis.
a) Suture: Thin layer of dense fibrous connective tissue.
Examples:
Cranial and facial bones….no movement (synarthrosis).
b) Syndesmosis: bones are connected by greater amount of
fibrous tissue.
More distance between bones than in a suture.
Examples:
Ligaments and membrane to attach tibia and fibula… some
movement (amphiarthrosis).
c ) Gomphosis: teeth is embedded in the alveolar sockets of
Gomphosis
maxilla and mandible….periodontal ligaments-made of dense fibrous
connective tissue hold tooth in place.
No movement (synarthrosis).
Connective Tissue
I. Connective tissue proper-Cells and Matrix (fibers & fluid ground substance)
C. Dense connective tissue- composed of densely packed fibers with dispersed
fibroblasts  gives strength.
i) Dense regular/Fibrous connective tissue- collagen fibers are all oriented in same
direction
…appear like a strong rope.
Have limited blood supply  slower repair of injuries.
Tendons: strong attachment of muscles to the bones.
Ligaments: strong attachment of bones to the bones at the joint.
Fibroblasts
Fibers
Structural Classification of Joints - Cartilaginous
Cartilaginous joints:
- Bones are connected by cartilage.
- Some synarthrosis….some amphiarthrosis.
a) Synchondrosis: bones are connected by hyaline cartilage.
No movement (synarthrosis).
Examples:
Epiphyseal plates in a growing long bone.
Costal cartilage to connect ribs to sternum.
b) Symphysis: bones are connected by a fibrocartilage disc.
Slight movement (amphiarthrosis)
Examples:
Intervertebral discs to connect vertebrae.
Pubic symphysis to form pelvic girdle.
Connective Tissue
Classification of connective tissue:
III. Supporting connective tissue- has fewer types of cells with matrix that has denser
network of fibers with gelatinous/solid ground substance.
Provides protection and supports softer tissues and organs.
A. Cartilage: has collagenous and elastic fibers with jelly-like ground substance
called chondroitin sulfate.
Chondrocytes – cartilage cells are located in spaces called lacuna.
Has no blood vessels or nerves….cells are nourished by diffusion….slow growth
and repair.
Depending on the type and ratio of fibers and matrix, cartilage can be:
Hyaline cartilage – sternum, part of ribcage, covers ends of long bones, in tracheal wall.
Fibrocartilage – makes up vertebral discs, pads in knee joint.
Elastic cartilage – found in external earlobe.
Hyaline
Fibro
Elastic
Chondrocyte
Lacuna
Matrix
Structural Classification of Joints - Bony
Bony joints:
Frontal
bone
- Form when fibrous/cartilaginous joints ossify.
- No space between the bones.
- Obviously immovable (synarthrosis).
Synostosis:-
i) Examples of fibrous joint ossification (Bones were initially
connected by fibrous tissue (suture)  became completely
ossified  transform into a single bone with no visible suture
lines.
2 frontal bones…fuse by age 6.
2 Mandible…fuse before birth.
Ilium, ischium and pubis…fuse after birth to form coxal/hip bone.
Mandible
ii) Example of cartilaginous joint ossification-Epiphyseal lines of
mature long bones.
Ilium
Pubis
Ischium
Coxal/
Hip bone
Structural Classification of Joints - Synovial
Most common in the body…TMJ, shoulder, elbow, fingers, hip, knee, toes.
Freely movable joints…diarthrosis.
Structure of a synovial joint
a) Synovial cavity: space/cavity between the bones with no blood vessels or nerves.
b) Articular/Joint capsule: a sleeve-like membrane that encloses and holds the bones in place. Divided into
2 layers:
Outer fibrous capsule: dense connective tissue membrane…continuous with periosteum and allows
ligament attachment.
Inner synovial membrane: secretes viscous synovial fluid that fills synovial cavity… lubricates the
joint, provides nutrients to the tissue in the joint, picks up wastes, WBCs protect from infections and cleans
up debris resulting from wear and tear.
c) Articular cartilage: cartilage cap that covers and protects the ends of the bones.
Knee Joint – Example of Synovial Joint
Knee-sagittal section
Quadriceps
muscle
Quadriceps
tendon
Femur
Bursa
Patella
Fat pad
Meniscus
Articular
cartilage
Meniscus
Tibia
Patellar
ligament
Tibial
tuberosity
Posterior
Anterior
Joint involving femur and tibia.
Synovial joint….joint with space/cavity.
Freely movable….diarthrosis.
Synovial cavity: space/cavity between femur and
tibia.
Articular cartilage: cartilage caps that cover and
protects the ends of the femur and tibia.
Articular/Joint capsule: sleeve-like membrane
that encloses the joint, holds femur and tibia in
place, secretes synovial fluid.
Meniscus/Articular discs: a pad of fibrocartilage
inserted to make femur and tibia fit better.
Fat pads: localized masses of adipose tissuesupport and fill spaces in the joint.
Patella- located on the patellar surface (anterior
distal surface) of femur.
Tendon of the thigh muscle (Quadriceps)
encloses patella (called sesamoid bone) 
becomes patellar ligament  attaches to tibial
tuberosity of tibia.
Bursa: synovial fluid filled sac found between skin
and patella…reduces friction between patella
and skin-shock absorber.
Knee Joint-Ligaments
Several ligaments to further support the knee joint.
Tibial collateral ligament (TCL): medial ligament that connects tibia to femur.
Fibular collateral ligament (FCL): lateral ligament that connects fibula to femur.
Anterior cruciate ligament (ACL) and Posterior cruciate ligament (PCL): form a
cross in the intercondylar fossa between femur and tibia….most often injured due
to sudden extension of the knee joint.
Movements
Movement at a joint depends on how the
bones fit, how tendons and ligaments
attach.
Joints can have a range of motion…from no
movement  freely movable joints.
For free movement at the synovial joints,
specific terms are used to precisely
describe the movement.
How are you going to remember
the terminology?
Practice…Practice…Practice
Movements
Three simple categories to describe the types of movements:
1. Gliding
2. Angular
3. Rotation
….and then there are special movements
Movements – Gliding (1)
Gliding:
Bones have tight articular capsules  only
allow surfaces to move back and forth and
from side to side with respect to one another
 no significant alteration of the angle
between the bones.
Examples:
Carpal bones of wrist
Tarsal bones of ankle
Sacroiliac joint
Acromioclavicular joint
Sternoclavicular joint
Movements – Angular (2)
Flexion
Hyperextension
Angular:
Bones move to increase or decrease in the angle between bones.
Flexion: movement that decreases the angle between the bones.
Extension: movement that increases the angle between the bones.
Hyperextension: continuation of extension beyond anatomical position.
Movements – Angular (2)
Circumduction
Angular:
Abduction: movement away from the midline of the body.
Adduction: movement towards the midline of the body.
Circumduction: distal end goes through circular movement while proximal end
remains stable.
Movements – Rotation (3)
Lateral Rotation: rotating a limb away from the midline of the body.
Medial Rotation: rotating a limb towards the midline of the body.
Supination: movement of the forearm  to face palm up.
Pronation: movement of the forearm  to face palm down.
Movements – Special Movements
Lateral flexion
1) Inversion-twisting movement of the foot, turns sole inward.
Eversion- opposite movement.
2) Dorsiflexion (ankle flexion)-bending of foot/toes upward (toes up).
Plantarflexion (angle extension)-bending of foot/toes downward (toes down).
3) Opposition- touching the thumb to each finger.
4) Protraction- anterior movement of a body part in the horizontal plane.
Retraction- posterior movement of a body part in the horizontal plane.
5) Depression- Movement of a body part in an inferior direction.
Elevation- Movement of a body part in an superior direction.
6) Lateral flexion- bending the spine away from the midline of the body (cervical and thoracic).
Classification of Synovial Joints
Examples:
- Acromioclavicular
- Claviculosternal
- Intercarpal
- Sacroiliac
Classification of Synovial Joints
Classification of Synovial Joints
The carpometacarpal joint
at the base of the thumb
concave
convex
Classification of Synovial Joints
Joint Disorders
Synovitis: inflammation of synovial membrane  inflammation of the joint.
Torn cartilage: tearing of meniscus/articular discs during aggressive sports activity
 increases friction  discomfort  may require surgery.
Bursitis: inflammation of bursa caused by trauma, infection or arthritis.
Dislocation/Luxation: the bones are pushed  articulation surfaces are forced out of
position can cause damage of articular cartilage and ligaments, and distort
articular capsule  sever pain.
Subluxation: partial dislocation  not as severe.
Joint Disorders
Rheumatism: painful joint due to bones, tendons, ligaments.
Arthritis: inflammation of a joint.
Rheumatoid arthritis: autoimmune disease of smaller joints where WBCs attack
joint tissue  swelling (edema), pain, erosion of articular cartilage  immovable
and distorted fingers.
Osteoarthritis/Degenerative arthritis: cumulative wear and tear of joint
surfaces/genetic factors affecting collagen formation restricts joint movement.
Gouty arthritis: defective gene, diet  overproduction of uric acid  forms
crystals in synovial joints  inflammation and breakdown of articular cartilage 
swelling and pain.
Arthroscopy: examination of the joint using an arthroscope  determine damage.
Arthroplasty: the surgical reconstruction and/or total replacement of degenerated
joints.
Hip arthroplasty – acetabulum, head of femur are replaced by prefabricated
prostheses made from polyethylene, acrylic cement and screws.