Physiology of Joints Flashcards
What are the three types of joints?
- Synovial
- Fibrous
- Cartilaginous
Within a synovial joint, what is the inner aspect of the fibrous capsule lined by?
Synovial membrane
(composed of vascular connective tissue with capillaries and lymphatics)
What type of cells are synovial cells and what is thier function?
Fibroblasts
They produce synovial fluid
What is a simple synovial joint?
A synovial joint with one pair of articular surfaces
What is a compond synovial joint?
A synovial joint with more than one pair of articular surfaces
(e.g. the elbow)
Joint lubrication is achieved by which three things?
- Interstitial fluid - from cartilage
- Hyaluronic acid (mucin) - derived from the synovium
- Lubricin (a glycoprotein) - derived from the synovium
Why does synovial fluid have a high viscosity?
Hyaluronic acid (mucin)
The synovial fluid is a constant pool.
True or false?
False
The synovial fluid is continously removed and replenished via the synovial membrane
Which two properties of synovial fluid change during movement?
- Elasticity
- Viscosity
e.g. during rapid movement, elasticity increases and viscosity decreases
Describe normal synovial fluid properties
- Normally around 3.5ml present (in knee)
- Clear and colourless
- <200 WBCs
- High viscosity
If synovial fluid is opaque what does this suggest?
The synovial fluid is septic
High white cell counts in the synovial fluid may suggest which two things?
- There is an inflammatory process (e.g. arthritis)
- The synovial fluid has become septic (e.g. infective arthritis)
Synovial joints are known by which other name?
Diarthrosis
Which means two articulations.
Arthritis - inflammation of articulation
What is the main purpose(s) of articular cartilage?
- Provides a smooth surface with low friction to prevent wear and tear
- Distributes contact pressure over a larger surface area
Hyaline cartilage, the cartilage type usually associated with articulation, is composed mainly of which three components?
- Water
- Type II collagen
- Proteoglycans
The extracellular matrix of the cartilage comprised what percentage of total cartilage volume?
98%
Where does the articular cartilage receive nutrients and O2 from?
Synovial fluid
(Articular cartilage is avascular - nutrients and O2 diffuse from the synovial fluid into the extracellualr matrix, and chondrocytes)
Which catabolic factors may chondrocytes secrete to break down the extracellular matrix?
- Tumour necrosis factor (TNF)-a
- Interleukin (IL)-1
These prevent proteoglycan synthesis
Which anabolic factors may chondrocytes secrete in order to build up the extracellualr matrix?
- Tumour growth factor (TGF)-β
- Insulin-like growth factor (IGF)-1
These cause proteoglycan synthesis
Increased levels of which two things suggest cartilage breakdown?
- Serum and synovial keratin sulphate
- Type II collagen in synovial fluid
Can give clues in diagnosis and/or act as seritity markers for osteoarthritis or rheumatoid arthritis
In simple terms, what gives rise to rheumatolid arthritis?
The proliferation and inflammation of synovial cells
An osteoarthritis knee may show which distinctive physical and histological features?
- Thickened capsule
- Hypertrophied synovial membrane
- Fibrillated articular cartilage
- Cyst formation
- Osteophyte formation (bony projections from joint margins)
- Sclerosis in subchondral bone
Goutry arthritis is caused by a deposition of what?
Uric acid crystals
Pseudo-gout is caused by deposition of what?
Calcium pyrophosphate crystals
(rhomboid shaped)
