SKELETAL JOINTSDr. Deepak K Gupta

Joints (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

Sutures

Gomphoses

Syndesmoses

Cartilaginous

Synchondroses

symphyses

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: Sutures

Figure 8.1a

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: Syndesmoses

Figure 8.1b

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: Synchondroses

Figure 8.2a, b

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

Cartilaginous Joints: Symphyses

Figure 8.2c

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: General Structure

Figure 8.3a, b

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

Types of Synovial Joints

Plane joints

Articularsurfaces are essentially flat

Allow only slipping or gliding movements

Only examples of nonaxialjoints

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

Types of Synovial Joints

Figure 8.7b

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

Pivot Joints

Figure 8.7c

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

Condyloid, or Ellipsoidal, 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

Saddle Joints

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

Ball-and-Socket Joints

Clinical Aspect

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

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