A&P @ LCC by Dr. Prince

Ch 8 Joints
Home | Letter | News | Grades | Chapter Outlines | Ask Me

Objectives
  • Know selected key terms
  • Define articulation
  • List and describe the functional and structural classification of joints and give examples of each
  • Describe the characteristics of all synovial joints
  • Describe the function and structure of tendon sheaths and bursae
  • Describe common body movements
  • Describe 6 types of synovial joints based on movement and give examples of each
  • Know the major structural components of the knee

The six types of diarthroses and examples of each.

  1. Planar joint - intercarpal, intertarsal, vertebrocostal, sternoclavicular, acromioclavicular
  2. Hinge joint - knee, elbow, ankle, interphalangeal
  3. Pivot - atlanto-axial, proximal ends of radius and ulna
  4. Condyloid - radiocarpal
  5. Saddle - trapezium and metacarpal of thumb
  6. Ball-and-socket - shoulder, hip

Enter content here

Joints (Articulations)

Weakest parts of the skeleton

Articulation – site where two or more skelletal structures 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

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

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: General Structure

Synovial joints all have the following

Articular cartilage

Joint (synovial) cavity

Articular capsule

Synovial fluid

Reinforcing ligaments

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 Movement

Rotation

The turning of a bone around its own long axis

Examples

Between first two vertebrae

Hip and shoulder joints

Special Movements

Supination and pronation

Inversion and eversion

Protraction and retraction

Elevation and depression

Opposition

Types of Synovial Joints

Plane joints

Articular surfaces are essentially flat

Allow only slipping or gliding movements

Only examples of nonaxial 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

Lateral and medial tibiofemoral joints

Synovial Joints: Knee Ligaments and Tendons – Anterior View

Tendon of the quadriceps femoris muscle

Lateral and medial patellar retinacula

Fibular and tibial collateral ligaments

Patellar ligament

Synovial Joints: Knee –
Other Supporting Structures

Anterior cruciate ligament

Posterior cruciate ligament

Medial meniscus (semilunar cartilage)

Lateral meniscus

Synovial Joints: Knee –
Posterior Superficial View

Adductor magnus tendon

Articular capsule

Oblique popliteal ligament

Arcuate popliteal ligament

Semimembranosus tendon

Synovial Joints: Shoulder (Glenohumeral)

Ball-and-socket joint in which stability is sacrificed to obtain greater freedom of movement

Head of humerus articulates with the glenoid fossa of the scapula

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

Synovial Joints: 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 and strong ligaments

Synovial Joints: Hip Stability

Acetabular labrum

Iliofemoral ligament

Pubofemoral ligament

Ischiofemoral ligament

Ligamentum teres

Synovial Joints: Hip Stability

Synovial Joints: Elbow

Hinge joint that allows flexion and extension only

Radius and ulna articulate with the humerus

Synovial Joints: Elbow Stability

Annular ligament

Ulnar collateral ligament

Radial collateral ligament

Synovial Joints: Elbow Stability

Sprains

The ligaments reinforcing a joint are stretched or torn

Partially torn ligaments slowly repair themselves

Completely torn ligaments require prompt surgical repair

Cartilage 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

Osteoarthritis: Course

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

Rheumatoid Arthritis: Course

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