Joints

Joints

• A joint is the location at which 2 or more bones make contact

• Joints, also called articulations, have 2 functions:

1. They hold bones together securely2. They give the rigid skeleton mobility• Joints are classified in 2 ways: Functionally and

Structurally

Functionally

• The functional classification focuses on the amount of movement allowed by the joint

• There are:1. Synarthroses: Immovable joints2. Amphiarthroses: Slightly movable joints3. Diarthroses: Freely movable joints• Synarthroses and Amphiarthroses are restricted

mainly to the axial skeleton• Diarthroses predominate in the limbs

Structurally

• Structurally, there are:1. Fibrous joints2. Cartilaginous joints3. Synovial joints• As a general rule, fibrous joints are immovable

and synovial joints are freely movable and most cartilaginous joints are amphiarthrotic

Fibrous Joints

• In fibrous joints, the bones are united by fibrous tissue

e.g. sutures of the skull

Cartilaginous Joints

• In cartilaginous joints, the bone ends are connected by cartilage

• Cartilaginous joints allow more movement between bones than a fibrous joint but less than the highly mobile synovial joint

e.g. intervertebral joints

Synovial Joints• Synovial joints are those in which the

articulating bone ends are separated by a joint cavity containing synovial fluid

• All synovial joints have 4 distinguishing features:

1. Articular cartilage2. Fibrous articular capsule3. Joint cavity4. Reinforcing ligaments

Synovial Joints• Articular cartilage: covers

the ends of the bones forming the joint

• Fibrous articular capsule: The joint surfaces are enclosed by a sleeve or capsule of fibrous connective tissue and the capsule is covered with a smooth synovial membrane

Synovial Joints

• Joint cavity: the articular capsule encloses a cavity, called the joint cavity, which contains lubricating synovial fluid

• Reinforcing ligaments: the fibrous capsule is usually reinforced with ligament (connection between bone to bone)

Inflammatory Disorders• Arthritis: describes over 100 different

inflammatory or degenerative diseases that damage the joints

• Acute forms of arthritis usually result from bacterial invasion and are treated with antibiotic drugs

• Chronic forms of arthritis include: osteoarthritis, rheumatoid arthritis, and gouty arthritis

Osteoarthritis (OA)• The most common form of

arthritis• Also called “wear and tear”

arthritis• Affects the articular

cartilages: over the years, there is a softening , fraying and eventual breaking down of the cartilage

• As the disease progresses, the exposed bone thickens and extra bone tissue, called bone spurs, grows around the margin of the eroded cartilage

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Rheumatoid Arthritis (RA)

• It is an autoimmune disease: a disorder in which the body’s immune system attempts to destroy its own tissue

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Gouty Arthritis (gout)

• A disease in which uric acid accumulates in the blood and may be deposited as crystal in the soft tissues of joints

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