Ch 8. Joints.

Ch 8. Joints

Joints Or articulations Sites where two bones meet
2 fundamental functions 1. Motility 2. Hold skeleton together - Weakest part of skeleton

Classification of Joints
Classified by structure and function Structural – material binding Fibrous Cartilaginous Synovial joints Function – Amount of movement Synarthroses – immovable Amphiarthroses – slightly movable Diarthroses – freely movable General – fibrous = immobile Synovial – freely movable Cartilaginous - both

Fibrous Joints Bones joined by fibrous tissue
Dense fibrous connective tissue No joint cavity present Most are immovable 3 types Sutures Syndesmoses gomphoses

Fibrous Joints 1. Sutures “seams” Only between bones of skull
Rigid slices knit bone together During middle age – ossifies – closed sutures – synostoses Immobile = protection

Joint held together with very short,
(a) Suture Joint held together with very short, interconnecting fibers, and bone edges interlock. Found only in the skull. Suture line Dense fibrous connective tissue Figure 8.1a

Fibrous Joints 2. Syndesmoses – Bones connected by ligaments
Only cords or bands of fibrous tissue Amount of movement depends on length of connecting fibers

(b) Syndesmosis Joint held together by a ligament.
Fibrous tissue can vary in length, but is longer than in sutures. Fibula Tibia Ligament Figure 8.1b

Fibrous Joints 3. Gomphoses – Peg in socket fibrous joint Tooth joint
Teeth embedded in sockets – periodontal ligament

(c) Gomphosis “Peg in socket” fibrous joint. Periodontal
ligament holds tooth in socket. Socket of alveolar process Root of tooth Periodontal ligament Figure 8.1c

Cartilaginous Joints Unit articulating bones Lack joint cavity
Not highly mobile 2 types – Synchondroses Symphyses

Cartilaginous Joints 1. Synchondroses –
Bones united by bar or plate of hyaline cartilage Epiphyseal plates in long bones of children Costal cartilage of first rib

(c) Gomphosis “Peg in socket” fibrous joint. Periodontal
ligament holds tooth in socket. Socket of alveolar process Root of tooth Periodontal ligament Figure 8.1c

Cartilaginous Joints 2. Symphyses – “growing together”
Intervening pad or plate of fibrocartilage Compress able and resilience Amphiarthrotic joints Designed for strength and flexibility

Bones united by fibrocartilage
(b) Symphyses Bones united by fibrocartilage Body of vertebra Fibrocartilaginous intervertebral disc Hyaline cartilage Pubic symphysis Figure 8.2b

Synovial Joints “joint eggs”
Articulating bones are separated by a fluid filled joint cavity Freedom of movement Freely moveable diarthroses

Synovial Joints General Structure
6 distinguishing characteristics: 1. Articular Cartilage – glassy smooth hyaline – articular cartilage Thin, spongy cushions absorb compression 2. Joint (Synovial) Cavity – joint cavity – potential space with a small amount of synovial fluid 3. Articular Capsule – 2 layered articular capsule or joint capsule Inner synovial membrane – loose CT 4. Synovial Fluid – occupies all free space Derived by filtration Viscous, egg white consistency Slippery weight bearing film – reduces friction

5. Reinforcing Ligaments – band like ligaments Usually – capsular or intrinsic ligaments – thickened parts of fibrous capsule Outside capsule – distinct – extracapsular ligaments Deep to it – intracapsular ligaments 6. Nerves and blood vessels – richly supplied with sensory nerve fibers Some detect pain Most monitor joint positions and stretch Richly supplied with capillary beds – produce filtrate

Other Components – Cushioning fatty pads Articular discs – menisci – wedges of fibrocartilage

Ligament Joint cavity (contains synovial fluid) Articular (hyaline)
cartilage Fibrous capsule Articular capsule Synovial membrane Periosteum Figure 8.3

Brusae And Tendon Sheaths
Associated with joints Bags of lubricants Ball bearings – reduce friction Bursae – flattened fibrous sacs Thin film of synovial fluid Occur where ligaments, muscles, skin, tendons, or bones rub together Tendon Sheath – Elongated bursae wraps completely around tendon subjected to friction Where several tendons crowded together

Coracoacromial ligament Subacromial bursa Humerus resting Cavity in
bursa containing synovial fluid Bursa rolls and lessens friction. Humerus head rolls medially as arm abducts. Humerus moving (b) Enlargement of (a), showing how a bursa eliminates friction where a ligament (or other structure) would rub against a bone Figure 8.4b

Stability of Synovial Joints
Stabilized – so do not dislocate Stability depends on – Shape of articular surfaces Number and position of ligaments Muscle tone

1. Articular Surfaces – Shapes determine movements possible Minor role in stability Many joints – shallow sockets – non-complementary articulating surfaces When large – socket deep – stability vastly improved

2. Ligaments – more ligaments – stronger Brace joints 3. Muscle Tone – muscle tendons cross joints Tendons taught at all times Muscle tone – low levels of contractile activity in relaxed muscles keep them muscles healthy and ready to react

Movements Allowed by Synovial Joints
Muscle origin – attached to immobile or less movable bone Insertion – attached to movable bone Muscle contract – insertion moves towards origin Nonaxial movement – slipping movements only – no axis Uniaxial movements – movement in 1 plane Biaxial movement – movement in 2 planes Multiaxial movement – movement in or around all 3 planes and axes

3 General Types of Movement
Gliding Angular Movements Rotations

1. Gliding Simplest One flat bone surface slides over another
Back and forth, side to side No angulations or rotation Intercarpal and intercostal joints

(a) Gliding movements at the wrist
Figure 8.5a

2. Angular Increase or decrease angle between 2 bones
Any plane of the body Include – flexion, extension, hyperextension, abduction, adduction and circumduction

(b) Angular movements: flexion, extension, and
Hyperextension Extension Flexion (b) Angular movements: flexion, extension, and hyperextension of the neck Figure 8.5b

2. Angular A. Flexion Bending movement Usually along sagittal plane
Decrease angle of joint Head toward chest

Extension Hyperextension Flexion
(c) Angular movements: flexion, extension, and hyperextension of the vertebral column Figure 8.5c

2. Angular B. Extension Reverse of flexion Occurs at same joints
Movement along sagittal plane Increase the angle Straightens a flexed limb or body part Ex. Straightening the knee Hyperextension – extension beyond anatomical position

Extension Hyperextension Flexion
(c) Angular movements: flexion, extension, and hyperextension of the vertebral column Figure 8.5c

2. Angular C . Abduction “moving away”
Movement of a limb away from the midline Along frontal plane

Abduction Circumduction Adduction
(e) Angular movements: abduction, adduction, and circumduction of the upper limb at the shoulder Figure 8.5e

2. Angular D. Adduction – “moving toward” Opposite abduction
Movement of a limb toward body midline

Abduction Circumduction Adduction
(e) Angular movements: abduction, adduction, and circumduction of the upper limb at the shoulder Figure 8.5e

2. Angular E. Circumduction –
Moving limb so it describes a cone in space Distal end of limb moves in a circle

3. Rotation Turning of bone around its long axis
1st – 2 cervical vertebrae Hip, shoulder Towards or away from midline

(f) Rotation of the head, neck, and lower limb
Lateral rotation Medial rotation (f) Rotation of the head, neck, and lower limb Figure 8.5f

Special Movements Do not fit into any of other categories
Supination “turning backwards” – radius around ulna Pronation – “turning forward” – radius around ulna

(a) Pronation (P) and supination (S)
(radius rotates over ulna) Supination (radius and ulna are parallel) (a) Pronation (P) and supination (S) Figure 8.6a

Special Movements Dorsiflexion – increase and decrease movement of foot, foot superior – approaches shin Plantar Flexion – pointing toes

(b) Dorsiflexion and plantar flexion
Figure 8.6b

Special Movements Inversion – sole of foot turns medially
Eversion – sole face laterally

(c) Inversion and eversion
Figure 8.6c

Special Movements Protraction – anterior movement in transverse plane
Retraction – posterior movement in a transverse plane

(d) Protraction and retraction
of mandible Retraction of mandible (d) Protraction and retraction Figure 8.6d

Special Movements Elevation – lift body part superiorly
Depression – moving elevated part inferiorly

(e) Elevation and depression
of mandible Depression of mandible (e) Elevation and depression Figure 8.6e

Special Movements Opposition – joint between metacarpal 1 and trapezium Movement of thumb

Opposition (f) Opposition Figure 8.6f

Types of Synovial Joints
6 categories – 1. Plane Joint – Flat Allow only short non-axial gliding movement No rotation Non-axial plane joints

Plane joint (intercarpal joint)
f Nonaxial Uniaxial Biaxial Multiaxial c b a Plane joint (intercarpal joint) a e d Figure 8.7a

2. Hinge Joints – Cylindrical end of bone conforms to trough shaped surface Motion – single plane Resembles mechanical hinge Permit flexion and extension only

Hinge joint (elbow joint)
f Nonaxial Uniaxial Biaxial Multiaxial c b b Hinge joint (elbow joint) a e d Figure 8.7b

3. Pivot Joints – Rounded end of bone conforms to “sleeve” or ring composed of bone Uniaxial rotation Atlas and dens joint Ex. Head side to side

Pivot joint (proximal radioulnar joint)
f Nonaxial Uniaxial Biaxial Multiaxial c b c Pivot joint (proximal radioulnar joint) a e d Figure 8.7c

4. Condyloid Joint – Also ellipsoidal joint Fits into complete depressions in another articulating surfaces oval Angular motion Ex. Radiocarpal joints

(metacarpophalangeal joint)
f Nonaxial Uniaxial Biaxial Multiaxial c b d Condyloid joint (metacarpophalangeal joint) a e d Figure 8.7d

5. Saddle Joints – Like condyloid joint but allow greater motion Both concave and convex areas Shaped like a saddle Carpometacarpal joint of thumb

Saddle joint (carpometacarpal joint of thumb)
Nonaxial Uniaxial Biaxial Multiaxial c b e Saddle joint (carpometacarpal joint of thumb) a e d Figure 8.7e

6. Ball and Sockets – Spherical or hemispherical head of one bone articulates with cup like socket of another Multiaxial and most freely moving synovial Universal movement – shoulder and hip

Ball-and-socket joint (shoulder joint)
f Nonaxial Uniaxial Biaxial Multiaxial c b f Ball-and-socket joint (shoulder joint) a e d Figure 8.7f

Synovial Joints- Knee Joint
Largest, most complex joint of body Three joints surrounded by a single joint cavity: Femoropatellar joint: Plane joint Allows gliding motion during knee flexion Lateral and medial tibiofemoral joints between the femoral condyles and the C-shaped lateral and medial menisci (semilunar cartilages) of the tibia Allow flexion, extension, and some rotation when knee is partly flexed

(a) Sagittal section through the right knee joint
Tendon of quadriceps femoris Femur Suprapatellar bursa Articular capsule Patella Posterior cruciate ligament Subcutaneous prepatellar bursa Synovial cavity Lateral meniscus Lateral meniscus Infrapatellar fat pad Anterior cruciate ligament Deep infrapatellar bursa Tibia Patellar ligament (a) Sagittal section through the right knee joint Figure 8.8a

(b) Superior view of the right tibia in the knee joint, showing
Anterior Anterior cruciate ligament Articular cartilage on lateral tibial condyle Articular cartilage on medial tibial condyle Lateral meniscus Medial meniscus Posterior cruciate ligament (b) Superior view of the right tibia in the knee joint, showing the menisci and cruciate ligaments Figure 8.8b

At least 12 associated bursae Capsule is reinforced by muscle tendons: E.g., quadriceps and semimembranosus tendons Joint capsule is thin and absent anteriorly Anteriorly, the quadriceps tendon gives rise to: Lateral and medial patellar retinacula Patellar ligament

(c) Anterior view of right knee
Quadriceps femoris muscle Tendon of quadriceps femoris muscle Patella Medial patellar retinaculum Lateral patellar retinaculum Tibial collateral ligament Fibular collateral ligament Patellar ligament Fibula Tibia (c) Anterior view of right knee Figure 8.8c

Capsular and extracapsular ligaments Help prevent hyperextension Intracapsular ligaments: Anterior and posterior cruciate ligaments Prevent anterior-posterior displacement Reside outside the synovial cavity

(d) Posterior view of the joint capsule, including ligaments
Femur Tendon of adductor magnus Articular capsule Oblique popliteal ligament Medial head of gastrocnemius muscle Lateral head of gastrocnemius muscle Popliteus muscle (cut) Bursa Fibular collateral ligament Tibial collateral ligament Arcuate popliteal ligament Tendon of semimembranosus muscle Tibia (d) Posterior view of the joint capsule, including ligaments Figure 8.8d

Synovial Joint – Shoulder Joint
Ball-and-socket joint: head of humerus and glenoid fossa of the scapula Stability is sacrificed for greater freedom of movement

Animation: Rotatable shoulder
Acromion of scapula Coracoacromial ligament Synovial cavity of the glenoid cavity containing synovial fluid Subacromial bursa Fibrous articular capsule Hyaline cartilage Tendon sheath Synovial membrane Fibrous capsule Tendon of long head of biceps brachii muscle Humerus (a) Frontal section through right shoulder joint PLAY Animation: Rotatable shoulder Figure 8.10a

Reinforcing ligaments: Coracohumeral ligament—helps support the weight of the upper limb Three glenohumeral ligaments—somewhat weak anterior reinforcements

Reinforcing muscle tendons: Tendon of the long head of biceps: Travels through the intertubercular groove Secures the humerus to the glenoid cavity Four rotator cuff tendons encircle the shoulder joint: Subscapularis Supraspinatus Infraspinatus Teres minor

(c) Anterior view of right shoulder joint capsule
Acromion Coracoid process Coracoacromial ligament Articular capsule reinforced by glenohumeral ligaments Subacromial bursa Coracohumeral ligament Subscapular bursa Greater tubercle of humerus Tendon of the subscapularis muscle Transverse humeral ligament Scapula Tendon sheath Tendon of long head of biceps brachii muscle (c) Anterior view of right shoulder joint capsule Figure 8.10c

of biceps brachii muscle
Acromion Coracoid process Articular capsule Glenoid cavity Glenoid labrum Tendon of long head of biceps brachii muscle Glenohumeral ligaments Tendon of the subscapularis muscle Scapula Posterior Anterior (d) Lateral view of socket of right shoulder joint, humerus removed Figure 8.10d

Synovial Joint – Elbow Joint
Radius and ulna articulate with the humerus Hinge joint formed mainly by trochlear notch of ulna and trochlea of humerus Flexion and extension only

(a) Median sagittal section through right elbow (lateral view)
Articular capsule Synovial membrane Humerus Synovial cavity Articular cartilage Fat pad Coronoid process Tendon of triceps muscle Tendon of brachialis muscle Ulna Bursa Trochlea Articular cartilage of the trochlear notch (a) Median sagittal section through right elbow (lateral view) Figure 8.11a

Synovial Joint – Elbow Joint
Anular ligament—surrounds head of radius Two capsular ligaments restrict side-to-side movement: Ulnar collateral ligament Radial collateral ligament

(b) Lateral view of right elbow joint
Humerus Anular ligament Radius Lateral epicondyle Articular capsule Radial collateral ligament Olecranon process Ulna (b) Lateral view of right elbow joint Figure 8.11b

Animation: Rotatable elbow
Articular capsule Anular ligament Humerus Coronoid process Medial epicondyle Ulnar collateral ligament Radius Ulna (d) Medial view of right elbow PLAY Animation: Rotatable elbow Figure 8.11d

Synovial Joint - Hip (Coxal) Joint
Ball-and-socket joint Head of the femur articulates with the acetabulum Good range of motion, but limited by the deep socket Acetabular labrum—enhances depth of socket

Reinforcing ligaments: Iliofemoral ligament Pubofemoral ligament
Coxal (hip) bone Articular cartilage Ligament of the head of the femur (ligamentum teres) Acetabular labrum Femur Reinforcing ligaments: Iliofemoral ligament Pubofemoral ligament Ischiofemoral ligament Ligamentum teres Synovial cavity Articular capsule (a) Frontal section through the right hip joint Figure 8.12a

Synovial Joint - Hip (Coxal) Joint
Reinforcing ligaments: Iliofemoral ligament Pubofemoral ligament Ischiofemoral ligament Ligamentum teres

(c) Posterior view of right hip joint, capsule in place
Iliofemoral ligament Ischium Ischiofemoral ligament Greater trochanter of femur (c) Posterior view of right hip joint, capsule in place PLAY Animation: Rotatable hip Figure 8.12c

Iliofemoral Anterior inferior ligament iliac spine Pubofemoral
Greater trochanter (d) Anterior view of right hip joint, capsule in place Figure 8.12d

Temporomandibular Joint (TMJ)
Mandibular condyle articulates with the temporal bone Two types of movement Hinge—depression and elevation of mandible Gliding—e.g. side-to-side (lateral excursion) grinding of teeth Most easily dislocated joint in the body

(a) Location of the joint in the skull
Mandibular fossa Articular tubercle Zygomatic process Infratemporal fossa External acoustic meatus Lateral ligament Articular capsule Ramus of mandible (a) Location of the joint in the skull Figure 8.13a

(b) Enlargement of a sagittal section through the joint
Articular disc Articular tubercle Mandibular fossa Superior joint cavity Articular capsule Synovial membranes Mandibular condyle Ramus of mandible Inferior joint cavity (b) Enlargement of a sagittal section through the joint Figure 8.13b

Lateral excursion: lateral (side-to-side) movements of the mandible
Superior view Outline of the mandibular fossa Lateral excursion: lateral (side-to-side) movements of the mandible Figure 8.13c

Common Joint Injuries Sprains The ligaments are stretched or torn
Partial tears slowly repair themselves Complete ruptures require prompt surgical repair Cartilage tears Due to compression and shear stress Fragments may cause joint to lock or bind Cartilage rarely repairs itself Repaired with arthroscopic surgery

Torn meniscus Figure 8.14

Common Joint Injuries Dislocations (luxations)
Occur when bones are forced out of alignment Accompanied by sprains, inflammation, and joint immobilization Caused by serious falls or playing sports Subluxation—partial dislocation of a joint

Homeostatic Imbalances
Bursitis An inflammation of a bursa, usually caused by a blow or friction Treated with rest and ice and, if severe, anti-inflammatory drugs Tendonitis Inflammation of tendon sheaths typically caused by overuse Symptoms and treatment similar to bursitis

Arthritis – >100 different types of inflammatory or degenerative diseases that damage joints Most widespread crippling disease in the U.S. Symptoms; pain, stiffness, and swelling of a joint Acute forms: caused by bacteria, treated with antibiotics Chronic forms: osteoarthritis, rheumatoid arthritis, and gouty arthritis

Osteoarthritis (OA) Common, irreversible, degenerative (“wear-and-tear”) arthritis 85% of all Americans develop OA, more women than men Probably related to the normal aging process More cartilage is destroyed than replaced in badly aligned or overworked joints Exposed bone ends thicken, enlarge, form bone spurs, and restrict movement Treatment: moderate activity, mild pain relievers, capsaicin creams, glucosamine and chondroitin sulfate

Rheumatoid Arthritis (RA) Chronic, inflammatory, autoimmune disease of unknown cause Usually arises between age 40 and 50, but may occur at any age; affects 3 times as many women as men Signs and symptoms include joint pain and swelling (usually bilateral), anemia, osteoporosis, muscle weakness, and cardiovascular problems

Rheumatoid Arthritis (RA) cont RA begins with synovitis of the affected joint Inflammatory blood cells migrate to the joint, release inflammatory chemicals Inflamed synovial membrane thickens into a pannus Pannus erodes cartilage, scar tissue forms, articulating bone ends connect (ankylosis)

Figure 8.15

Rheumatoid Arthritis (RA) Treatment - Conservative therapy: aspirin, long-term use of antibiotics, and physical therapy Progressive treatment: anti-inflammatory drugs or immunosuppressants New biological response modifier drugs neutralize inflammatory chemicals

Gouty Arthritis – Deposition of uric acid crystals in joints and soft tissues, followed by inflammation More common in men Typically affects the joint at the base of the great toe In untreated gouty arthritis, the bone ends fuse and immobilize the joint Treatment: drugs, plenty of water, avoidance of alcohol

Lyme Disease – Caused by bacteria transmitted by the bites of ticks Symptoms: skin rash, flu-like symptoms, and foggy thinking May lead to joint pain and arthritis Treatment: antibiotics

Developmental Aspects
By embryonic week 8, synovial joints resemble adult joints A joint’s size, shape, and flexibility are modified by use Advancing years take their toll on joints: Ligaments and tendons shorten and weaken Intervertebral discs become more likely to herniate Most people in their 70s have some degree of OA Exercise that coaxes joints through their full range of motion is key to postponing joint problems

Ch 8. Joints.

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