chapter 8

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

Chapter 8Joints (Articulations)

Weakest parts of the skeleton Articulation – site where two or more bones meet Functions of joints

Give the skeleton mobility Hold the skeleton together


Classification of Joints: Structural Structural classification focuses on the material

binding bones together and whether or not a joint cavity is present

The three structural classifications are: Fibrous Cartilaginous Synovial


Classification of Joints: Functional Functional classification is based on the amount of

movement allowed by the joint The three functional classes of joints are:

Synarthroses – immovable Amphiarthroses – slightly movable Diarthroses – freely movable


Fibrous Structural Joints The bones are joined by fibrous tissues There is no joint cavity Most are immovable There are three types – sutures, syndesmoses, and

gomphoses


Fibrous Structural Joints: Sutures Occur between the bones

of the skull Comprised of

interlocking junctions completely filled with connective tissue fibers

Bind bones tightly together, but allow for growth during youth

In middle age, skull bones fuse and are called synostoses


Fibrous Structural Joints: Syndesmoses Bones are connected by

a fibrous tissue ligament Movement varies from

immovable to slightly variable

Examples include the connection between the tibia and fibula, and the radius and ulna


Fibrous Structural Joints: Gomphoses The peg-in-socket fibrous joint between a tooth

and its alveolar socket The fibrous connection is the periodontal ligament


Cartilaginous Joints Articulating bones are united by cartilage Lack a joint cavity Two types – synchondroses and symphyses


Cartilaginous Joints: Synchondroses A bar or plate of hyaline cartilage unites the bones All synchondroses are synarthrotic Examples include:

Epiphyseal plates of children Joint between the costal cartilage of the first rib and the sternum


Cartilaginous Joints: Symphyses

Hyaline cartilage covers the articulating surface of the bone and is fused to an intervening pad of fibrocartilage

Amphiarthrotic joints designed for strength and flexibility Examples include intervertebral joints and the pubic

symphysis of the pelvis


Pelvic Girdle (Hip)

Figure 7.27a


Synovial Joints Those joints in which the articulating bones are separated

by a fluid-containing joint cavity All are freely movable diarthroses Examples – all limb joints, and most joints of the body Synovial joints all have the following

Articular cartilage Joint (synovial) cavity Articular capsule Synovial fluid Reinforcing ligaments


Synovial Joints: General Structure

Figure 8.3a, b


Synovial Joints: Friction-Reducing Structures Bursae – flattened, fibrous sacs lined with synovial

membranes and containing synovial fluid Common where ligaments, muscles, skin, tendons, or bones

rub together Tendon sheath – elongated bursa that wraps completely

around a tendon


Synovial Joints: Stability Stability is determined by:

Articular surfaces – shape determines what movements are possible

Ligaments – unite bones and prevent excessive or undesirable motion

Muscle tone is accomplished by: Muscle tendons across joints acting as stabilizing factors Tendons that are kept tight at all times by muscle tone


Synovial Joints: Movement The two muscle attachments across a joint are:

Origin – attachment to the immovable bone Insertion – attachment to the movable bone

Described as movement along transverse, frontal, or sagittal planes


Synovial Joints: Range of Motion Nonaxial – slipping movements only Uniaxial – movement in one plane Biaxial – movement in two planes Multiaxial – movement in or around all three

planes


Gliding Movements One flat bone

surface glides or slips over another similar surface

Examples – intercarpal and intertarsal joints, and between the flat articular processes of the vertebrae


Angular Movement Flexion — bending movement that decreases the angle of

the joint Extension — reverse of flexion; joint angle is increased Dorsiflexion and plantar flexion — up and down

movement of the foot Abduction — movement away from the midline Adduction — movement toward the midline Circumduction — movement describes a cone in space


Gliding Movements One flat bone

surface glides or slips over another similar surface

Examples – intercarpal and intertarsal joints, and between the flat articular processes of the vertebrae


Angular Movement

Figure 8.5b


Angular Movement

Figure 8.5c, d


Angular Movement

Figure 8.5e, f


Rotation The turning of a bone

around its own long axis Examples

Between first two vertebrae

Hip and shoulder joints

Figure 8.5g


Special Movements

Figure 8.6a


Special Movements

Figure 8.6b


Special Movements

Figure 8.6c


Special Movements

Figure 8.6d


Special Movements

Figure 8.6e


Plane Joint Plane joints

Articular surfaces are essentially flat

Allow only slipping or gliding movements

Only examples of nonaxial joints

Figure 8.7a


Types of Synovial Joints Hinge joints

Cylindrical projections of one bone fits into a trough-shaped surface on another

Motion is along a single plane

Uniaxial joints permit flexion and extension only

Examples: elbow and interphalangeal joints


Pivot Joints Rounded end of one bone

protrudes into a “sleeve,” or ring, composed of bone (and possibly ligaments) of another

Only uniaxial movement allowed

Examples: joint between the axis and the dens, and the proximal radioulnar joint


Condyloid or Ellipsoidal Joints Oval articular surface of

one bone fits into a complementary depression in another

Both articular surfaces are oval

Biaxial joints permit all angular motions

Examples: radiocarpal (wrist) joints, and metacarpophalangeal (knuckle) joints


Saddle Joints Similar to condyloid

joints but allow greater movement

Each articular surface has both a concave and a convex surface

Example: carpometacarpal joint of the thumb


Ball-and-Socket Joints A spherical or

hemispherical head of one bone articulates with a cuplike socket of another

Multiaxial joints permit the most freely moving synovial joints

Examples: shoulder and hip joints


Synovial Joints: Knee Largest and most

complex joint of the body

Allows flexion, extension, and some rotation

Three joints in one surrounded by a single joint cavity

Femoropatellar joint Lateral and medial

tibiofemoral joints


Synovial Joints: Knee – Other Supporting Structures

Anterior cruciate ligament

Posterior cruciate ligament

Medial meniscus (semilunar cartilage)

Lateral meniscus


Synovial Joints: Shoulder Stability

Figure 8.11a


Synovial Joints: Elbow Annular ligament Ulnar collateral

ligament Radial collateral

ligament

Figure 8.10a


Synovial Joints: Shoulder Stability Weak stability is maintained by:

Thin, loose joint capsule Four ligaments – coracohumeral, and three

glenohumeral Tendon of the long head of biceps, which travels

through the intertubercular groove and secures the humerus to the glenoid cavity

Rotator cuff (four tendons) that encircles the shoulder joint and blends with the articular capsule


Synovial Joints: Shoulder Stability

Figure 8.11a


Synovial Joints: Hip Stability Acetabular labrum Iliofemoral ligament Pubofemoral ligament Ischiofemoral ligament Ligamentum teres

Figure 8.12a


Temporomandibular Joint

Figure 8.13a, b


Sprains The ligaments reinforcing a joint are stretched or

torn Partially torn ligaments slowly repair themselves Completely torn ligaments require prompt surgical

repairCartilage Injuries

• The snap and pop of overstressed cartilage• Common aerobics injury• Repaired with arthroscopic surgery


Dislocations Occur when bones are forced out of alignment Usually accompanied by sprains, inflammation,

and joint immobilization Caused by serious falls and are common sports

injuries Subluxation – partial dislocation of a joint


Inflammatory and Degenerative Conditions Bursitis

An inflammation of a bursa, usually caused by a blow or friction

Symptoms are pain and swelling Treated with anti-inflammatory drugs; excessive fluid may

be aspirated

Tendonitis Inflammation of tendon sheaths typically caused by overuse Symptoms and treatment are similar to bursitis


Arthritis More than 100 different types of inflammatory or

degenerative diseases that damage the joints Most widespread crippling disease in the U.S. Symptoms – pain, stiffness, and swelling of a joint Acute forms are caused by bacteria and are treated

with antibiotics Chronic forms include osteoarthritis, rheumatoid

arthritis, and gouty arthritis


Osteoarthritis (OA) Most common chronic arthritis; often called “wear-and-tear” arthritis Affects women more than men 85% of all Americans develop OA More prevalent in the aged, and is probably related to the normal aging

process OA reflects the years of abrasion and compression causing increased

production of metalloproteinase enzymes that break down cartilage As one ages, cartilage is destroyed more quickly than it is replaced The exposed bone ends thicken, enlarge, form bone spurs, and restrict

movement Joints most affected are the cervical and lumbar spine, fingers, knuckles,

knees, and hips


Osteoarthritis: Treatments OA is slow and irreversible Treatments include:

Mild pain relievers, along with moderate activity Magnetic therapy Glucosamine sulfate decreases pain and

inflammation


Rheumatoid Arthritis (RA) Chronic, inflammatory, autoimmune disease of unknown cause, with an

insidious onset Usually arises between the ages of 40 to 50, but may occur at any age Signs and symptoms include joint tenderness, anemia, osteoporosis,

muscle atrophy, and cardiovascular problems The course of RA is marked with exacerbations and remissions

RA begins with synovitis of the affected joint Inflammatory chemicals are inappropriately released Inflammatory blood cells migrate to the joint, causing swelling Inflamed synovial membrane thickens into a pannus Pannus erodes cartilage, scar tissue forms, articulating bone ends connect The end result, ankylosis, produces bent, deformed fingers


Rheumatoid Arthritis: Treatment Conservative therapy – aspirin, long-term use of

antibiotics, and physical therapy Progressive treatment – anti-inflammatory drugs or

immunosuppressants The drug Enbrel, a biological response modifier,

neutralizes the harmful properties of inflammatory chemicals


Gouty Arthritis Deposition of uric acid crystals in joints and soft

tissues, followed by an inflammation response Typically, gouty arthritis affects the joint at the

base of the great toe In untreated gouty arthritis, the bone ends fuse and

immobilize the joint Treatment – colchicine, nonsteroidal anti-

inflammatory drugs, and glucocorticoids


Developmental Aspects of Joints By embryonic week 8, synovial joints resemble adult joints Few problems occur until late middle age 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

Prudent exercise (especially swimming) that coaxes joints through their full range of motion is key to postponing joint problems

chapter 8

Business

flat articular

fibrous structural

gouty arthritis

articular

articular

rheumatoid

muscle tone

gliding movements