Type of hyaline cartilage covers the bone ends and makes smooth movements possible.
It distributes the load across joints,minimizing the peak stress on subchondral bone.
Relatively acellular. No vascular,neural or lymphatic supply Has little capacity to heal after injury. Wear resistant Low frictional Lubricated surface Slightly compressible and elastic
Differs from hyaline cartilage in that it is not covered by perichondrium. Collagen fibres of articular cartilage
matrix are of type-II which exhibit
characteristic cross banding of collagen fibres exsist.
Young cartilage – typically white,smooth,
glistening and compressible Aged – thinner,less cellular,firmer and
more brittle with less regular surface and yellowish opacity. Thickness – Bony end plate
ZONES OF ARTICULAR CARTILAGE 1) SUPERFICIAL ZONE Not smooth,layer of hyaluronic acid LAMINAR SPLENDENS –most superficial Elongated chondrocytes,relatively inactive 2) TRANSITIONAL ZONE Thicker ,cells rounded & larger, arranged
pairs Actively engaged in matrix component
synthesis
DEEP ZONE - Largest zone - Largest collagen fibrils,highest proteoglycan content, lowest water ZONE OF CALCIFIED CARTILAGE - Irregular cells pyknotic nuclei /stability - TIDE MARK - Continuous with subchondral plate
PERICELLULAR MATRIX - CHONDRON - Modulate the pressure transmission - regulation of chondrocyte response to pressure,prevent squashing TERRITORIAL MATRIX - Fibrillar basket - surrounds the pericellular matrix
INTERTERRITORIAL MATRIX - Largest matrix compartment - parellel arrangement of collagen
fibrils - responsible for mechanical
properties.
Less than 1% of tissue volume Rarely divide normally / cell density
decreases with age Synthesize matrix components-
proteoglycans constantly renewed,collagen
slow turnover CILIUM – Regulation of matrix turnover
COLLAGEN - Type II ,major (90%) - Characteristic cross banded fibrils - Type IX,X,XI minor NON-COLLAGENOUS PROTEINS - Link protein /binding GAG to hyaluronic
acid - Chondronectin and anchorinCII
PROTEOGLYCANS - Family of glycoproteins large protein
core attached to GAG side chains. - Form of large aggregates - Provide the resilience to A.C under
load
Mature A.C – diffusion from synovial fluid
Immature A.C – vascular channels in sub chondral bone,base of cartilage,S.F Energy – anerobic pathway Microenviroment:high CO2 & low O2 Survive for more than 2 days after
death
CHONDROMALACIA: A.C damage or degeneration OUTER BRIDGE Classification: Based on arthroscopic exam
GRADE O- Normal GRADE I- Swelling & softening of intact
A.C GRADE II-Fissuring & fibrillation over
small area < .5 inch GRADE III- Same over larger area > .5
inch GRADE IV- Erosion of subchondral bone
Mitosis induced by laceration,compression, Superficial lacerations – doesn’t cross tidemark
donot heal. Penetrates the subchondral bone- reach S.C vessels initiate healing process Fibrinous arcade – scaffold that directs the mesenchymal cells to form F.C matrix Repaired tissue – intermediate between H.C & F.C / poor biomehanical properties.
Biphasic material – solid & liquid phase Fibre reinforced gel- mutually repellant macromolecules binds water-osmotic P. Water resides in microscopic pores and
flow of the water induced by pressure
gradient or matrix contraction.Flow pressure provides load support & minimize
stress on matrix.
JT loading & motion required to maintain normal adult A.C Immobilisation of JT cause rapid loss of proteoglycans so deformation in
response to load will increase. Excessive use or increased loading
affect
Debridement of chondral flaps and removal
of loose chondral fragments. Abrasion chondroplasty Microfracture
Periosteal & Perichondrial grafting Autologous cartilage implantation Osteochondral autograft Osteochndral allograft