Joint pain Flashcards
Fibrous joint examples: sutures
- Sutures: found exclusively in the skull, bone plates held together by sharpey fibres
fibrous joint examples: syndesmosis
- Syndesmosis: two adjacent bones are linked by a strong fibre/ligament
Fibrous joint examples: Gomphoses
- Gomphoses: the roots of the teeth (the pegs) fit into their sockets in the mandible and maxilla and are the only examples of this type of joint.
Cartilaginous joints:: synchondroses (primary) (3)
- Definition
- Lifespan (2)
- Advancing centres of ossification separated by hyaline cartilage
- Most are temporary (e.g. epiphyseal growth plates) and fuse in adulthood
- Some persist, e.g. costal cartilages, which allow some flexibility
Cartilaginous joints: symphyses (secondary) (3)
- Definition
- Role (2)
- Fibro-cartilage pads between a.c. of adjacent bones
- Allows slight movement (e.g intervertebral discs and symphysis pubis)
- Some symphyses fuse during growth (e.g. sacral and coccygeal discs)
Synovial joints:
- Definition
- Cavity role
- variation
- Articulating bones separated by synovial cavity filled with synovial fluid
- Cavity gives synovial joints a wide range of movement
- Different types allow movement in varying planes
Different types of synovial joint: (6)
P (G)
P
H
S
E
B
- Plane (gliding)
- Pivot
- Hinge
- Saddle
- Ellipsoid
- Ball and socket
Synovial joint component tissues: Joint capsule
Outer fibrous capsule
- Location
- Structure
- Innervation
- Blends with periosteum and tendons
- Composed of dense irregular connective tissue
- Highly innervated
Synovial joint component tissue: joint capsule: Inner synovial membrane (synovium)
- Location
- Role
- Lines joint cavity bar articulations
- Produces constituents of synovial fluid
Synovium (inner synovial membrane):
- Layers (2)
- Supporting layer or stroma (sub-intima)
- Lining of synovial cells in contact with synovial fluid (intimal cells)
synovium (inner synovial membrane):
synovial cell type A
- Derived from bone marrow
- Secretory and phagocytic functions
Synovium (inner synovial membrane):
synovial cell type B
- Type of fibroblast
- Role in synthesis of hyaluronic acid
Articular cartilage:
- Contains
- Cell type
- Contains cells, fibres and matrix arranged in zones
- Cells are chondrocytes; density varies with age and morphology varies in each zone
Articular cartilage:
- Fibre composition
- Matrix composition
- Fibres are collagen; mostly type II, small amounts of types VI, IX and XI
- Matrix composed mostly of large aggregated proteoglycans (aggrecan) and some smaller PGs (decorin and biglycan)
Subchondral bone:
- Structure
- Variation in children
- Use as a marker
- Cortical bone plate supported by trabecular bone
- In children, perforated by blood vessels where it provides route for nutrient exchange
- Shows biochemical and structural changes in some joint diseases
Ligaments:
- Defintion
- Structure
- Structural benefits
- Regions of fibrous capsule thicken to form ligaments
- Composed of dense regular CT comprising parallel collagen fibres (mainly type I)
- This gives ligaments great tensile strength along their length
Menisci: (2)
- Discs or pads of fibrocartilage
- Located within capsule, they provide extra strength and support
Bursae: (2)
- Often found where tendon passes over bone
- Modified bursae form tendon sheaths around tendons
Synovial fluid: (2)
- Fills joint cavity and bursae
- Important role in lubrication and cartilage nutrition
Mechanical function of synovial joints:
- Role
- Shape of articulating surfaces ….
- General rule
- Synovial joints allow movement whilst providing stability
- Shape of articulating surfaces influences type and range of movement
- Increased mobility associated with reduced stability
Improving stability of synovial joints: (2)
- Bones enlarge at ends to provide large contact area
- Deformable cartilage and menisci also increase contact area
Effects of shear forces on synovial joints:
Causes friction leading to:
- Loss of energy
- Increase in temperature
- Wear and tear at bearing surface
Role of joint lubrication:
- Role
- Lubrication types (2)
- Mixed
- Reduces the damaging effects of friction
- Fluid-film and boundary
- In some circumstances, both types operate together (mixed lubrication)
Lubrication failure: (2)
- Can lead to increased friction and fibrillation of cartilage surface
- Roughened, fibrillated surface results in increased friction and wear/cartilage damage
Effects of mechanical loading:
- General effect
- Repetitive cyclic loading ……
- High levels of mechanical loading ….
- Causes fluid changes in cartilage, sustained compression squeezes fluid out, reducing cartilage thickness and ability to equalise stress
- Repetitive cyclic loading can cause proteoglycan loss at cartilage surface and distortion of collagen network
- High levels of mechanical loading can damage cartilage surface and kill chondrocytes
Osteoarthritis: cartilage surface changes (3)
- Fibrillation
- Erosion
- Cracks
Osteoarthritis: other cartilage changes (5)
- Cartilage softening
- Chondrocyte necrosis
- Regeneration
- Cell cluster
- Cell proliferation
Osteoarthritis: changes in the bone (4)
j
M
S
E
- Joint space narrowing
- Marginal osteophytes
- Sclerosis
- Eburnation
Osteoarthritis: changes in synovium (2)
- Mild to moderate inflammation
- Neovascularization
Osteoarthritis: clinical signs (7)
S
M
J
T
W
C
I
- Swelling
- muscle wasting
- Joint effusions
- Tenderness
- Warmth
- Crepitus
- Instability
Osteoarthritis: symptoms (5)
- Onset is slow and insidious
- Use-related pain
- Joint stiffness and inactivity
- Reduced range of joint motion
- Functional limitation
Causes of knee pain in OA:
- Cartilage damage
- Bone remodelling
- Meniscal tears
- Ligament injuries
- Synovium
Trabecular bone (spongy):
- 15% of bone
- Endo skeleton
- Calcium reservoir
- Haematopoeisis
Cortical bone:
- Prevalence
- Role
- 85%
- Endoskeleton
Horizontal trabeculae importance:
- Increases bone strength by 16X
Material properties of bone:
- Skeletal mineralisation:
- Collagen crosslink formation
Bone remodelling:
- Description
- Timespan
- Provides
- Role
- Lifelong process involving discrete sites throughout the skeleton
- Each cycle takes 3-4 months
- Provides supply of calcium for calcium homeostasis
- Maintains bone integrity by replacing sites of fatigue damage
RANK signalling in osteoclasts:
- Stromal cells produce and present RANKL molecules
- These bind to receptors on osteoclast precursor cells, activating them into mature osteoclasts
OPG importance:
- Produced by stromal cells to “mop up” excess RANKL molecules, providing a break from the resorption process
Disorders associated with defective osteoclasts: Osteopetrosis
- CLC-7 chloride channel deficiency
- Deficiency of a3 subunit of the vacuolar H+ - ATPase proton pump
- Carbonic anhydrase II deficiency
Disorders associated with defective osteoclasts: Pycnodysostosis
- Mutation of
- Causes
- Presentations (3)
- Cathespin K gene mutation
- Defective degradation of organic bone matrix
- Skull deformities with delayed cranial structure closure
- Short stature and phalanges
- Abnormally dense but brittle bones
Osteoblast growth factors: Bone morphogenetic proteins (BMPs)
- Mechanism
- Mutation in BMP type I receptor ACVR1 causes
- Activation of BMP type I receptor on cell surface causes a downstream effect, causing osteoblast differentiation
- fibrodysplasia ossificans progressiva
Osteoblast growth factors: Wnt signally pathway
- LRP5
- Sclerostin
- Activating mutations of LRP5 cause high bone mass
- Inactivation of sclerostin causes sclerostosis
Sclerostin deficiency:
- Causes
- Clinical presentation
- Causes a high bone mass phenotype
- Mandibular overgrowth, facial palsy and deafness
Bone remodelling in osteoporosis: trabecular bone (4)
- Increased activation frequency
- Increased erosion depth
- Reduced trabecular thickness
- Trabecular perforation
Bone remodelling in osteoporosis: cortical bone (3)
- Structural changes also affect cortical bone, characterised by
- endosteal expansion
- cortical thinning
- an increase in size and number of haversian canals
