Joints

Classification of Joints Functional classification

(Focuses on amount of movement) Synarthroses (immovable joints) Amphiarthroses (slightly movable joints) Diarthroses (freely movable joints)

Structural classification(Based on the material binding them and presence or

absence of a joint cavity) Bony fusion Fibrous Cartilagenous Synovial

Table of Joint Types Functional across

Structural down

Synarthroses(immovable joints)

Amphiarthroses(some movement)

Diarthroses(freely movable)

Bony Fusion Synostosis (frontal suture; epiphyseal lines)

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

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

Fibrous joints

Bones connected by fibrous tissue: dense regular connective tissue

No joint cavity Slightly immovable or

not at all Types

Sutures Syndesmoses

Sutures Only between

bones of skull Fibrous tissue

continuous with periosteum

Ossify and fuse in middle age: now technically called “synostoses”= bony junctions

Syndesmoses

In Greek: “ligament”

Bones connected by ligaments only

Amount of movement depends on length of the fibers: longer than in sutures

Gomphoses Is a “peg-in-socket”

Only example is tooth with its socket

Ligament is a short periodontal ligament

Cartilagenous joints

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

Synchondroses (singular: synchondrosis) Sympheses (singular: symphesis)

Synchondroses

Literally: “junction of cartilage” Hyaline cartilage unites the bones Immovable (synarthroses) Examples:

Epiphyseal plates Joint between first rib’s costal cartilage and

manubrium of the sternum

Sympheses Literally “growing together” Fibrocartilage unites the bones

Slightly movable (amphiarthroses) Resilient shock absorber Provide strength and flexibility

Hyaline cartilage on articular surfaces of bones to reduce friction

Examples Intervertebral discs Pubic symphysis of the pelvis

Synchondroses and sympheses

Also pubic symphsis

Synovial joints

Include most of the body’s joints

All are diarthroses (freely movable)

All contain fluid-filled joint cavity

General Structure of Synovial Joints

1. Articular cartilage Hyaline Spongy cushions absorb

compression Protects ends of bones

from being crushed

2. Joint (synovial) cavity Potential space Small amount of synovial

fluid

General structure of synovial joints (cont.)

3. Articular (or joint) capsule Two layered Outer*: fibrous capsule of

dense irregular connective tissue continuous with periosteum

Inner*: synovial membrane of loose connective tissue (makes synovial fluid)

Lines all internal joint surfaces not covered by cartilage*

*

**

General structure of synovial joints (cont.)

4. Synovial fluid Filtrate of blood Contains special glycoproteins Nourishes cartilage and

functions as slippery lubricant

5. Reinforcing ligaments (some joints) Capsular (most) – thickened

parts of capsule Extracapsular Intracapsular

General structure of synovial joints (cont.)

6. Nerves Detect pain Monitor stretch (one of the

ways of sensing posture and body movements)

7. Blood vessels Rich blood supply Extensive capillary beds in

synovial membrane (produce the blood filtrate)

General structure of synovial joints

Articular disc or meniscus (literally “crescent”) Only some joints Those with bone ends of different shapes or fitting poorly Some to allow two kinds of movement (e.g. jaw) Of fibrocartilage Examples: knee TMJ (temporomandibular joint) sternoclavicular joint

Some joints…

Bursae and tendon sheaths

Contain synovial fluid Not joints but often associated with them Act like ball bearings Bursa means “purse” in Latin

Flattened sac lined by synovial membrane Where ligaments, muscles, tendons, or bones

overlie each other and rub together Tendon sheath

Only on tendons subjected to friction

Bursae and tendon sheaths

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: hor i 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

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)

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