Lecture 29 - Cartilage Flashcards
3 types of cartilage
- Fibrocartilage
- Elastic cartilage
- Hyaline Cartilage
fibrocartilage is found where
Elastic cartilage is found where
Hyaline cartilage is found where
What are the 4 features of a synovial joint
- Hyaline Cartilage: Articular surfaces of the bone
- Joint Capsule: Connective tissue sleeve surrounding the joint
- Synovial Membrane: Lining of joint capsule
- Synovial Fluid: Viscous fluid that lubricates articular surfaces
Joint capsule
Important for function of synovial joint
Joint capsule is innervated by
Nerves from those supplying the muscle acting on the joint
What 2 sensations occur at the joint capsule
1) Proprioception
2) Pain
T or F: The joint capsule can be stretched or contracted which affects joint function
T
Function of a continuous passive motion machine
Passive motion performed by mechanical device that moves joint slowly and continuously through controlled ROM
2 functions of hyaline cartilage
1) Resist compression/loading of joints
2) Smooth surface to allow joint ROM
4 characteristics of hyaline cartilage
- Smooth
- Avascular (diffusion for nutrients)
- No innervation
- Low friction
2 components of hyaline cartilage and what makes up each component
- Cells -> Chondrocytes
- ECM:
->Fibrillar Component: Type II collage and elastin
->Interfibrillar component: Water and proteoglycans
Proteoglycans affect
Hydration of tissue
Where are proteoglycans found
Connective tissue
Proteoglycans consist of a core protein which are attached to
Glycosaminoglycan chains
Hyaline cartilage are avascular so how do they receive nutrition and eliminate wastes
Diffusion through synovial fluid with assistance by joint movements (aid diffusion)
What are the 4 layers of hyaline cartilage
- Superficial/Tangential Zone (Zone 1): Functions against shear forces with collagen orientated parallel to joint surface
- Intermediate/Transitional Zone (Zone 2): Withstand shearing and compressive forces with collagen organized in meshwork
- Deep/Radiate Zone (Zone 3): Highest proteoglycan content to resist compressive forces
- Calcified Cartilage Zone (Zone 4): Anchors cartilage to underlying bone
List the 5 grades of hyaline cartilage injury
4 characteristics of hyaline cartilage injury
- No vascular response
- Chondrocytes increase proteoglycan synthesis but regeneration will be slow if at all (mainly at peripheries)
- If injury does NOT penetrate subchondral bone, the articular cartilage does not heal and cartilage degeneration takes place
- If injury penetrates subchondral bone, damaged hyaline cartilage is replaced by fibrocartilage and biomechanical properties will be mismatched
What are 3 goals of surgical management for chondral and osteochondral defects (hyaline cartilage)
- Reduce symptoms
- Improve joint congruence by restoring joint surface with best possible tissue
- Prevent additional cartilage deterioration
What 2 arthroscopic options promote healing for cartilage tear
- Lavage and debridement
- Microfracture
What is lavage
Removes loose intraarticular tissue debris and inflammatory mediators that are generated by synovial lining which could allow chondrocytes to increase biosynthetic activity but results are temporarily short-lived
What is microfracture
Disruption of subchondral bone to induce bleeding which could result in fibrocartilaginous tissue repair
What are 2 structural changes in articular cartilage due to osteoarthritis
- Macroscopic: Softening and erosion
- Microscopic: Loss of cartilage layers and clefts found through cartilage
How does osteoarthritis change the ECM of articular cartilage
Loss of PG content leading to a more permeable solid matrix which decreases the tissues ability to withstand compression.
Also observe softening and disturbed organization of collagen
What 3 affects happen to the subchondral bone as a result of
degeneration from osteoarthritis
- Increased subchondral plate thickness (increased stiffness decreasing shock-absorbance)
- Formation of new bone at joint margins (osteophytes)
- Development of subchondral bone cysts
What 2 structural changes in articular cartilage and peri-articular bone occur due to osteoarthritis
- Loss of cartilage thickness causing joint laxity
- Alteration in stresses at joint surface enhancing disease progression
T or F: Radiographic findings are strongly related to symptom and pain severity of osteoarthritis
F, it is not
How would you describe the pain of osteoarthritis
Episodic/intermittent initially that is triggered by specific activities
What are 4 secondary effects of osteoarthritis
1) Muscle weakness
2) Altered gait and balance
3. Decreased activity
4) Loss of ROM
Fibrocartilage
Articulating structures between vertebrae (intervertebral disc)
What 3 adjacent structures is intervertebral disc connected to
- vertebrae at rim
- anterior and posterior longitudinal ligaments
- Hyaline cartilage end plates superiorly and inferiorly
What are 2 distinct components of intervertebral discs and function
1) Annulus fibrosis (outer) Made of type 1 collagen that retains the nucleus and takes up and distributes the forces exerted by the nucleus during activities
2) Nucleus pulposis (inner): Gelatinous and acts as a shock absorber (made up of proteoglycans)
Describe the intervertebral disc blood supply
Does not have its own direct blood supply.
Limited with only the outer mm of annulus fibrosis containing capillaries from surround soft tissue
Describe the intervertebral disc nerve supply
Limited with only the outer mm of annulus fibrosis containing free nerve endings (pain) and mechanoreceptors (GTO, Ruffini, Pacinian)
What happens to the intervertebral discs as we age
- Degeneration begins as early as 1st decade and prominent by end of 2nd decade where spondylosis (Degenerative disc disease) can occur
- Peripheral annulus widens and nucleus pulposis loses proteoglycan content
- Decreased ability to withstand forces with most adults have some level of degenerative disc disease
Disc Herniation
Nucleus pushes through a tear in the annulus
Meniscus and where it can be found
Type of fibrocartilage found in the knee
Describe knee meniscus blood supply
Anterior and posterior horns are well vascularized
Describe knee meniscus nerve supply
Anterior and posterior horns along with outer 1/3 of meniscus contain mechanoreceptors and proprioceptors, but the inner 2/3 of meniscus lack nerve supply
Image of meniscus tears
What are 2 characteristics of tissue healing for knee meniscus
- Injury in peripheral zone results in hematoma at tear site
- Tear site heals with fibrovascular scar that is continuous with normal meniscal fibrocartilage but does not achieve strength of normal meniscus fibrocartilage
Where is the labrum found
Shoulder and hip
3 function of the labrum
- Deepens socket joint
- Increases contact between joint surfaces
- Evens load distribution across joint surfaces
Describe labrum of shoulder blood supply
Does not have its own blood supply but does receive vascularization from neighbouring tissues
Describe the nerve supply of labrum in the shoulder
Contains free nerve endings in its periphery and may be responsible for proprioceptive feedback
Describe labrum blood supply in the hip
Supplied to outer 1/3 of labrum by obturator, superior gluteal, and inferior gluteal arteries
Describe labrum nerve supply of the hip
Superior and inferior portion are innervated by free nerve endings and nerve sensory end organs to detect pain, pressure, and deep sensation
What are 4 factors of aging that affect cartilage
- Size of proteoglycans decrease with age
- Decrease in chondroitin
- Decreased water content (less efficient with mechanical loads)
- Loss of thickness of cartilage (alter joint laxity and therefore mechanical loading
What are 7 factors of immobility that affect cartilage
- Increased fatty connective tissue in joint space
- Increased adhesion between folds of synovium
- Increased atrophy of cartilage
- Weakened ligaments at insertion sites
- Regional osteopenia
- Decreased proteoglycans
- Increased water content in cartilage
