Basic Science of Joints

8/10/2019 Basic Science of Joints

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Joints

1. Articular tissues

a. Cartilage

b. Synoviumc. Meniscus

2. Arthroses


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CARTILAGE

Type of cartilage

a. Growth plate ( physeal ) cartilage

b. Fibrocartilage : tendon and ligament

insertion into bonec. Elastic cartilage ( trachea )

d. Fibroelastic cartilage ( menisci)

e. Articular cartilage.


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ARTICULAR CARTILAGE

Function

decreases in friction and distributes loads

Characteristic

Avascular , aneural and alymphatic.

PH: 7,4Composition

a. Water (65-80% of wet weight)for nutrition andlubrication,allow deformation of cartilage surface in response tostress.

b. Collagencollagen type 2, provide cartilaginous framework andtensile strength, half life 25 years

c. Proteoglycanproduced by chondrocytes, provide compressivestrength ,


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Proteoglycans are secreted into extracellular

matrixcomposed as glycosaminoglycans

(GAGs)

GAGs subtypechodroitin sulfate and

keratin sulfate

Proteoglycans half life of 3 months.

Proteoglycans provide elastic strength ,

produce cartilages porous structure and trap

and hold water.


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D. Chondrocytesproduce collagen ,

proteogylcan and enzymes for cartilage

metabolism

E. Other matrix components :

1. adhesives : fibronectin , chondronectin ,

anchorin

2. lipids


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ARTICULAR CARTILAGE LAYER

A. Gliding zone( super

B. Transitional zone( middle )

C. Radial zone ( deep)D. Tide mark

E. Calcified zone


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Articular Cartilage Metabolism

1. Collagen synthesis .

2. Collagen catabolismenzymatic processes

3. Proteoglycan sintesis.4. Proteoglycan catabolism.


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Articular Cartilage Growth Factor

1. PDGFhealing of cartilage laceration

2. TGF- stimulates proteoglycan synthesis

while suppressing syhthesis of type II

collagen

3. Fibroblast growth factorstimulates DNA

synthesis in adult articular chondrocytes.

4. Insulin-like Growth factorI (IGF-I)

stimulate DNA and cartilage matrix synthesis

in adult articular.


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ARTICULAR CARTILAGE HEALING

The fibrocartilage is produced byundiffrentiated marrow mesencyhmal stemcell.

Injury of articular cartilage1. Type 1 injury: limited due to chondrocytes

2. Type 2 injury : articular surface do not cross

the tide mark3. Type 3 injury : laceration extend below

tidemark


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SYNOVIUM

Types

Type A : fagosit

Type B : produce syonovial fluid , fibroblast-like cells

Type C : intermediate cell type

Components and function Synovial fluid consists : hyaluronic acid ,

lubricin , proteinase, collagenasse and

prostaglandin


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SYNOVIUM

FUNCTION

1. Lumbricate articular cartilagelubricin

2. Provides nourishment through diffusion

HISTOLOGY

Chronic inflammation of synoviumaccumulation of

lymphocytes , hyperplasia intima lining, neutrphils

absence.


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MENISCUS

Deepens the articular surface of a variety

synovial joints .

More elastic and less permeable than articular cartilage,triangular semilunar structure.

Meniscus transmits 50% of the force across the jointwhenthe knee is extended and up to 90 % in deep flexion.

Meniscus composed fibroelastic cartilage , collagen fiber(type 1), proteoglycans glcoprotein and cellular elements.

The cell responsible for menischal healing is the

fibrochondrocyte. Peripheral acute meniscal tears width < 4 mm have the best

healing characteristics


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Documents

Basic Science of Joints