ANATOMY OF JOINTS

By- Dr. Armaan SinghBy- Dr. Armaan Singh

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=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

FIBROUS JOINTS

Bones connected by fibrous tissue: dense regular connective tissue

No joint cavity

Slightly immovable or

not at all

Types

Sutures

Syndesmoses

Gomphoses

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

“Weeping” lubricatioin

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

SOME 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

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: or the angle between two bones DO TOGETHER

Flexion

Extension

Abduction

Adduction

Circumduction

Rotation

Special movements

Pronation

Supination

Dorsiflexion

Plantar flexion

Inversion

Eversion

Protraction

Retraction

Elevation

Depression

Opposition

SPECIAL MOVEMENTS

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

1. 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 movements

Demonstrate 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)