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Chapter 9Joints = Articulations

Where ANY bones come together

Developed by John Gallagher, MS, DVM

Classification of Joints

1. Function 1. Based on ROM

2. Structure 1. Based on structure

and whether there is a joint cavity

1. Functional Classification of Joints

1) Synarthrosis (no movement) • Fibrous (Sutural or Gomphosis) • Cartilaginous (Synchondrosis often becomes

synostosis) • Bony Fusion (Synostosis) 2) Amphiarthrosis (little movement) • Fibrous (Syndesmosis – tibia to fibula) • Cartilaginous (Symphysis) 3) Diarthrosis (free movement)

Three types of movement Six Types of structure

2. Structural Classification of Joints (Marieb utilizes Structural Classification (See Table 9.1)

u 1. Fibrous (no joint cavity) u Almost no movement, little CT u E.g, Sutures in calvarium

u 2. Cartilaginous u E.g., Symphysis pubis, IV disks

u 3. Synovial – by far most important

1. Fibrous (no joint cavity)

u Sutures u Only in the skull

u Lambdoidal, Coronal, etc. u Minimal movement u Growth allowed

u Syndesmosis (pl. syndesmoses) u Ligamentous attachments u Minimal movement u E.g., distal tibia to distal fibula

u Gomphosis (pl. gomphoses) u Teeth u Periodontal ligament

2. Cartilaginous = Union by cartilage

u Synchondrosis u Hyaline cartilage u Epiphyseal plates u May become

synostosis u Symphysis

u Fibrocartilage u Intervertebral Disks,

symphysis pubis

3. Synovial (with egg white) – most important! p 209

1. Articular Cartilage 1. Hyaline

2. Joint Cavity or Space 3. Articular capsule

1. Synovial Membrane 2. Joint capsule

4. Synovial Fluid 1. Nourishes 2. Cushions 3. Lubricates

5. Reinforcing Ligaments 6. Nerves and blood

supply

3. Synovial, cont’d

u Depends on: u Shape of articular

surfaces u Supporting Ligaments u Muscle Tone

Joint Stability

Bursae and Tendon Sheaths

u Bags of synovial fluid u Lubrication and cushion

u Tendons u Ligaments

n.b.: Tendinitis, Synovitis

Three Types of Motion at Synovial Joints

u Linear motion = gliding

u Angular motion : u flexion, extension,

hyperextension u ab-, adduction

u Rotation u left - right, internal or medial,

external or lateral u C1 – C2 , leg/foot, radius

u Special Movements u Pronation, supination

Special Movements

u Supination, Pronation u Radius/ulna

u Dorsiflexion, plantar flexion u Elevation, depression u Eversion, Inversion

Table 9.4

6 types of Synovial Joints

1 Plane (Gliding) Joint 2 Hinge Joint 3 Pivot Joint 4 Condyloid (Ellipsoidal) Joint 5 Saddle joint 6 Ball & Socket joint

See (p 216, fig 9.8)

Representative Articulationsu Temporomandibular Joint

u Mostly hinge joint, some gliding and rotation

u Articular disc

Intervertebral articulations

u Gliding joints between vertebrae u Articular facets (synovial

joints u Intervertebral discs:

(Amphiarthroses)  u annulus fibrosus: tough

outer layer (fibrocartilage) u nucleus pulposus: soft,

gelatinous core u Account for ~25% of

vertebral column height – H2O loss during aging

Glenohumeral (shoulder) Joint

Greatest range of motion (due to loose capsule and shallow glenoid)

u Most frequently dislocated

u Stability provided by rotator cuff (p 223)

Hip (coxofemoral joint)

u Deep well fitted ball and socket joint

u Stabilization: u Extracapsular and

intracapsular ligaments (ligamentum teres = ligamentum capitis femoris)

u Strong joint capsule u Extensive surrounding

musculature

Knee

u Much more complex than elbow

u Less stable than other hinge joints u Some gliding and rotation

u Structurally 3 separate joints

u No single joint capsule

More Knee

u Extra- and intracapsular structures u Medial and lateral

meniscus u Cruciate ligaments u Collateral ligaments

(extracapsular) u Fat Pads u Patella and Patellar

Tendon/ligament Anterior Posterior

Knee, sagittal section

Ant. Cruc. Lig.

The infamous ACL

u Twisting u Soccer, skiing, etc.

u 8X more common in women u Hormones u Strength u Geometry

u Surgery is optional u Several techniques

u Post-op period

Total Knee Replacement

Total Knee Replacement

The Ankle and Foot

u Hinge Joint u Deltoid and three Lateral

Ligaments u Calcaneous = Heel Bone

u Calcaneal/Achilles Tendon u Talus articulates with tibia u Intertarsal and

Tarsometatarsal Joints u Cunieform bones u Metarsal and phalangeal

bones u Similar to the hand