JointsFunction: hold

bones together & Increase mobility

Classification of Joints

Structural classification -binding material & presence or absence of a joint cavity Fibrous Cartilagenous Synovial

Functional classification - amount of movement Synarthroses (immovable joints) Amphiarthroses (slightly movable joints) Diarthroses (freely movable joints)

Fibrous joints/Synarthroses

Bones connected by dense regular connective tissue No joint cavity Slightly immovable or

not at all Types

Sutures Between tibia/fibula

Cartilagenous joints/ Amphiarthoroses

Articulating bones united by cartilage Lack a joint cavity Not highly movable Ex

Intervertebral discs Pubic symphysis of the pelvis

Amphiarthroses

Also pubic symphsis

Synovial joints/ Diarthroses

Include most of the body’s joints

freely movable

All contain fluid-filled joint cavity

General Structure of Synovial Joints1. Articular cartilage

Spongy cushions absorb compression

Protects ends of bones from being crushed

2. Synovial cavity Potential space Small amount of synovial

fluid

3. Articular capsule layered covering of joint

General structure of synovial joints (cont.)

4. Synovial fluid Nourishes cartilage and

functions as slippery lubricant

5. Reinforcing ligaments (some joints) link bones

6. Nerves Detect pain Monitor stretch

7. Blood vessels

General structure of synovial joints

Joint stability Articular surfaces

Shape usually plays only minor role Some deep sockets or grooves do provide stability

Ligaments Usually the more, the stronger the joint Can stretch only 6% beyond normal length before tear Once stretched, stay stretched

Muscle tone Constant, low level of contractile force Keeps tension on the ligaments Especially important at shoulders, knees, arches of

foot

Movements allowed by synovial joints

Gliding Angular movements: or the angle between

two bones DO TOGETHER

Flexion Extension Abduction Adduction Circumduction

Rotation Special movements

Special movements

Pronation Supination Dorsiflexion Plantar flexion Inversion Eversion

Protraction Retraction Elevation Depression Opposition

Joint movements pics (from Marieb, 4th ed.)

Synovial joints classified by shape

(of their articular surfaces)

Plane (see right) Hinge (see right) Pivot Condyloid Saddle Ball-and-socket

Shoulder (glenohumeral) joint Stability sacrificed for

mobility Ball and socket: head of

humerus with glenoid cavity of scapula

Glenoid labrum: rim of fibrocartilage

Thin, loose capsule Strongest ligament:

coracohumeral Muscle tendons help

stability Disorders

Selected synovial joints

Rotator cuff muscles add to stability

Biceps tendon is intra-articular

Elbow joint

Hinge: allows only flexion and extension

Annular ligament of radius attaches to capsule

Capsule thickens into: Radial collateral

ligament Ulnar collateral

ligament Muscles cross joint Trauma

Wrist joint

Two major joint surfacesSeveral ligaments stabilize

1. Radiocarpal joint Between radius and

proximal carpals (scaphoid and lunate)

Condyloid joint Flexion extension

adduction, abduction, circumduction

2. Intercarpal or midcarpal joint Between the proximal

and distal rows of carpals

Hip (coxal) joint

Ball and socket Moves in all axes but

limited by ligaments and deep socket

Three ext. ligaments “screw in” head of femur when standing Iliofemoral Pubofemoral Ischiofemoral

Acetabular labrum diameter smaller than head of femur Dislocations rare

Ligament of head of femur supplies artery

Muscle tendons cross joint

Hip fractures common in elderly because of osteoporosis

Right hip, AP view

Knee joint

Largest and most complex joint Primarily a hinge Compound and bicondyloid: femur and

tibia both have 2 condyles Femoropatellar joint shares joint cavity At least a dozen bursae

Prepatellar Suprapatellar

Lateral and medial menisci “torn cartilage”

Capsule absent anteriorly

Capsular and extracapsular ligaments Taut when knee

extended to prevent hyperextension

Patellar ligament Continuation of

quad tendon Medial and lateral

retinacula

Fibular and tibial collateral ligaments Called medial and

lateral Extracapsular

Oblique popliteal Arcuate popliteal

Cruciate ligaments

Cross each other (cruciate means cross)

Anterior cruciate (ACL) Anterior intercondylar area

of tibia to medial side of lateral condyl of femur

Posterior cruciate Posterior intercondylar

area of tibia to lateral side of medial condyl

Restraining straps Lock the knee

Cruciate ligaments

Knee injuries

Flat tibial surface predisposes to horizontal injuries

Lateral blow: multiple tears

ACL injuries Stop and twist Commoner in women

athletes Heal poorly Require surgery

Ankle joint

Hinge joint Distal tibia and fibula to talus Dorsiflexion and plantar

flexion only Medial deltoid ligament Lateral ligaments: 3 bands

Anterior talofibular Posterior talofibular Calcaneofibular

Anterior and posterior tibiofibular (syndesmosis)

Right ankle, lateral view

Temporomandibular joint (TMJ)

Head of mandible articulates with temporal bone

Disc protects thin mandibular fossa of temporal bone

Many movementsDemonstrate movements together

Disorders common

Table of Joint Types

Functional across

Structural down

Synarthroses(immovable joints)

Amphiarthroses(some movement)

Diarthroses(freely movable)

Bony Fusion Synostosis (frontal=metopic suture; epiphyseal lines)

Fibrous Suture (skull only)-fibrous tissue is continuous with periosteum

Gomphoses (teeth)-ligament is periodontal ligament

Syndesmoses-ligaments only

between bones; here, short so some but not

a lot of movement (example: tib-fib

ligament)

Syndesmoses-ligament longer (example: radioulnar interosseous membrane)

Cartilagenous (bone united by cartilage only)

Synchondroses-hyaline cartilage (examples: manubrium-C1, epiphyseal plates)

Sympheses -fibrocartilage (examples: between discs, pubic symphesis

Synovial Are all diarthrotic

Sternoclavicular joint

Saddle joint Only other example is trapezium

and metacarpal 1 (thumb), allowing opposion

Sternum and 1st costal (rib) cartilage articulate with clavicle

Very stable: clavicle usually breaks before dislocation of joint

Only bony attachment of axial skeleton to pectoral girdle

Demonstrate movements together

Disorders of joints

Injuries Sprains Dislocatios Torn cartilage

Inflammatory and degenerative conditions Bursitis Tendinitis Arthritis

Osteoarthritis (“DJD” – degenerative joint disease) Rheumatoid arthritis (one of many “autoimmune” arthritites) Gout (crystal arthropathy)