Flashcards in Joint Disease Deck (51)
What are the two layers of a joint?
Fibrous joint capsule
Inner synovial fluid layer
What is subchondral bone?
Cortical bone beneath the cartilage of a joint
- provides support for articular cartilage
- Has Haversian system running parallel to the joint surface
Describe the synovial membrane...
Vascular connective tissue
- No basement membrane
- Functional continuation of vascular space
What are the different types of cells that can be found in a synovial membrane?
- Type A: macrophagic
- Type B: secretory and fibroblastic, possible functional adaptation
- Type C?: Transitional between A and Bs
What is synovial fluid composed of?
- Hyaluronic acid
- pro- MMP
- Eicosanoids (PGE2)
What are periarticular ligaments and joint capsules composed of?
Type I collagen
Describe the insertion points of periarticular ligaments...
Parallel bundles of collagen course through the fibrocartilage and calcified cartilage before inserting on bone
- reduces that chance of avulsion
- responds to physical stimuli by hyper/ atrophy
What are the three words that describe articular cartilage best?
Describe Articular Cartilage...
-- nutrition and metabolic waste removal through diffusion
What is important about synovial joint pressure?
They have a sub-atmospheric pressure when they are in neutral position
- This contributes to the stability of the joint
What are the layers of cartilage histologically?
- Tide mark
- Calcified cartilage
- Subchondral bone
What are the components of cartilage ECM?
- Tissue fluid
What are the mechanical properties of cartilage ECM?
- Tensile strength: type II collagen
- Compressive stiffness: the negatively charged glycosaminoglycans attract several times their weight in water
-- responsible for the compressive stiffness of the cartilage
Describe the lubrication of joints...
Hydrostatic "Weeping" lubrication
-- Lubrication under load
-- Water is squeezed out of the cartilage matrix
-- Low load lubrication
-- Hyaluronic acid and other molecules
Describe the biomechanical action of joints...
The correspondence of joints increases under load
- Increased stability
Stress is distributed
- to the epiphysis which deforms
-- subsequent bone remodelling
Muscles absorb large proportion of the load
What does bone remodelling aim to achieve?
Maximum strength and shock absorption capacity
What does maintaining joint integrity require?
- Healthy cartilage
- Healthy subchondral bone
- Congruent articular surface
- Extra-articular support (ligaments and muscles etc)
- Normal motion
What is DJD/ osteoarthritis?
A NON-INFLAMMATORY disorder of movable joints characterised by the degeneration and loss of articular cartilage and the development of new bone on joint surfaces and margins
What is the pathogenesis of DJD?
- ABNORMAL cartilage with flawed biomechanical properties undergoing NORMAL forces
- NORMAL healthy cartilage subjected to ABNORMAL micro/ major trauma
What are some examples of Normal stress on Abnormal cartilage?
- Inflammation of soft tissue
What are some examples of Abnormal stress on Normal cartilage?
- Cyclic trauma
- Athletic trauma
- Loss of stability i.e. fractures
- Joint congruence changes
- Remodelling and necrosis in SC bone
What does fibrillation of cartilage look like?
The cartilage surface looks like floating seaweed
What are cartilage wear lines usually caused by?
The presence of fragment in a join
Describe severe cartilage erosion...
SC bone exposed with no cartilage at all
What are the bony changes that occur with DJD?
- SC bone sclerosis
- Periarticular osteophytosis (bony growths)
- SC bone erosion/ lysis
- SC cyst formation
How can DJD be diagnosed?
- Clinical signs
- Diagnostic Imaging
- Synovial fluid analysis
- Surgical techniques
What are the clinical manifestations of DJD?
- Reduced range of motion
- Synovial fluid changes
Describe how the pain comes about in DJD...
- Synovium is stimulated (cartilage aneural)
- Periarticular soft tissues are highly innervated
- Effusion stimulates stretch receptors
- Periarticular fibrosis results in reduced compliance
- Periosteal inflammation
- SC bone pain and increased intramedullary pressure
Describe how DJD results in a reduced range of motion...
- Synovial proliferation (Acute)
- Articular fibrosis (chronic)
-- body trying to counteract stability
- Effusion causes pain which negatively feedback to muscles which then change their load to the joint