MSS03 Introduction To Degenerative Joint Disorders Flashcards
1
Q
Osteoarthritis
A
- Progressive loss of articular cartilage (hyaline cartilage)
- Attempted repair of the cartilage
- Remodelling and sclerosis of subchondral bone
- Subchondral bone cyst formation
- Marginal osteophyte
- Common, Age-related, Heterogeneous group of disorders characterised pathologically by
—> focal areas of **Loss of articular cartilage in synovial joints
associated with:
—> **Synovitis
—> **Subchondral bone change
—> **Osteophyte formation
2
Q
Articular cartilage
A
- Avascular (obtain nutrient by diffusion from bone)
- Aneural
- Alymphatic
- No capacity to repair structural damage due to injury / disease
Content: 1. Chondrocytes (1%) 2. ***Water (70%) 3. ECM (structural macromolecules) - ***Type II collagen (60%) - ***Proteoglycan —> Protein core + ***Glycosaminoglycan e.g. hyaluronic acid, chondroitin sulfate, keratan sulfate, dermatan sulfate) chains - ***Glycoproteins and Non-collagenous proteins
3
Q
Chondrocyte-matrix interactions
A
Chondrocytes:
—> degrade and synthesize **matrix macromolecules
—> synthesize and release **cytokines
Matrix:
—> **protects chondrocyte from mechanical damage
—> transduce and **transmits signals with loading
4
Q
Articular cartilage: Aging vs OA
A
- Structural changes
Aging: Stable
OA: Progressive - Water content
Aging: ↓
***OA: ↑ (swelling) - Collagen
Aging: ↑ cross-linking
***OA: Disruption of macromolecular organisation
5
Q
OA articular cartilage changes
A
- ***↑ water content
- slow progressive ***loss of proteoglycans
- change in arrangement and size of ***collagen fibres
6
Q
Primary OA
A
Joint overload —> surface damage
- ***Hips and knees
- ***DIP joint of hand (Heberden’s nodes)
- Other synovial joints
- CMC joint of **thumb
- MTP joint of **great toe
- facet joints of spine
- elbows
- shoulders
7
Q
What cause OA
A
Mixture of:
- Systemic factors —> predispose to disease
- Local mechanical factors —> distribution and severity
- Genetic foci: minor contributions
8
Q
Systemic factors
A
- Age
- Sex (female more common)
- Ethnicity
- ***Hormonal status
- Bone density
- ***Nutritional and metabolic factors
- DM
- obesity
- hypertension
- sarcopenia (muscle loss)
9
Q
Local mechanical factors
A
- ***Joint deformity / malalignment
- ***Obesity
- Joint injury
- Occupational factors
- Sports
- Muscle weakness
10
Q
Lower limb alignment
A
Normally:
Centre of Hip, Knee, Ankle —> straight line —> knee 微向內曲
Malalignment (Eccentric loading):
- ***Genu valgum (knock knee)
- ***Genu varum (bow leg)
11
Q
Prevalence of OA hip and knee
A
OA hip: more prevalent in whites
OA knee: more prevalent in Chinese
12
Q
Diagnosis of OA
A
EULAR (European League Against Rheumatism) 3 signs - Crepitus - Restricted ROM - Bony enlargement
3 symptoms
- Persistent pain
- Limited morning stiffness
- Reduced function
ACR (American College of Rheumatology)
- > 50
- <30 mins morning stiffness
- Crepitus
- Bony tenderness
- No enlargement
- No palpable warmth
13
Q
***Clinical features of OA
A
- ***Triphasic mechanical pain:
- With activities
—> ↑ when start to walk
—> ↓ after a while
—> ↑ again with long walk
- Severity
—> at rest
—> at night
—> need of pain killers
—> walking distance and walking aids
—> effect on daily activities, occupation, hobbies - ***Stiffness
- Gelling
—> after wake up
—> after prolonged immobility
- Effect on daily activities
—> hip: cannot put on socks
—> knee: cannot squat
- Physical examination
—> limitations of passive ROM - ***Crepitus
- on movement (palpable, due to loss of cartilage and chondral bone) - Bony enlargement
- Deformity
- Limping
- abnormal gait patterns
14
Q
***Pathoanatomy of OA (記)
A
-
Articular cartilage damage (narrowing joint space)
- grade 0-IV - ***Osteophyte formation (bone spur —> body try to ↑ SA to ↓ pressure on joint)
- ***Subchondral sclerosis
- thickening of subchondral bone plate —> white area instead of white line
- bone become denser —> sclerotic
- stronger but more brittle under higher stress
- cracks —> synovial fluid sips through cracks —> subchondral cysts - ***Subchondral cyst
15
Q
OA articular cartilage damage grading
A
Grade 0: Normal cartilage
Grade I: Cartilage becomes ***soft and swells (↑ water content: change in consistency)
Grade II: Partial-thickness defect with **fibrillation (shredded appearance) / **fissures (depressions)
Grade III: Increased amount of damage to the level of ***subchondral bone / fissures extend to subchondral bone
Grade IV: Exposed subchondral bone - ***Eburnation (bare bone)
16
Q
Biomechanics of OA
A
- Single-legged stance during walking
—> 3x body weight
—> weight of body part + force created by muscle contraction - Knee joint surface loads
—> 3x body weight during level ground walking
—> 4x body weight with stair walking
—> medial knee / tibia (60-70% stress)
—> ↑ varus malalignment (medial knee even bigger stress)
—> ↑ knee adduction moment - Patellofemoral joint surface loads
—> 2-3x body weight while descending stairs
—> ↑ deep knee bend
—> ↑ abnormal patellar height
—> ↑ abnormal tracking (knee cap shifting out of place)
17
Q
***Investigations of OA
A
- Plain radiographs (Kellgren Lawrence classification)
- **narrowing of joint space
- **marginal osteophyte
- **subchondral sclerosis
- **subchondral cyst
- body contour change / defect - MRI
- Meniscal tear (cannot be seen on X-ray)
—> traumatic
—> degenerative
- **Loose bodies
- **Cysts
—> Baker’s cyst / Popliteal cyst - Blood tests
- **normal white cell count
- **normal ESR (↑ ESR / CRP —> inflammatory rather than degenerative causes)
- normal bone profiles (Ca, PO4, alkaline phosphatase) - Joint aspiration
- clear straw colour
- total cell count <1000 / mm3
- **gram smear -ve, culture -ve
- **crystals -ve
—> urate crystal (Gouty arthritis)
18
Q
Management of OA
A
- Education and modify risk factors
- lifestyle modification (must walk more to strengthen cartilage, NOT advise to rest)
- ***weight loss
- walking aids
- understanding of disease - Physical
- ***muscle strengthening
—> core muscles
—> knee muscles
- ROM exercise
- muscle stretching
- aerobic exercises
- knee brace, shoe insoles - Pharmacological
- Acetaminophen
- NSAID
—> Non-selective
—> COX-2 specific inhibitor
- Topical agents
- Others
—> Narcotic analgesic
—> Anticonvulsants (Neuralgia)
—> Antidepressants - Cartilage supplements
- Glucosamine
—> substrate for synthesis of proteoglycans
- lack level I evidence
- placebo effect - Intra-articular injections
- Hyaluronate
—> Glycosaminoglycan
—> Visco-supplementation
——> supplement viscosity of joint fluid —> lubrication and cushioning
——> pain relief (incomplete, not always, lasts 6-9 months)
- Steroid (reserved for inflammatory causes)
—> anti-inflammatory
—> short term benefit
—> no >4 times in single joint within 1 year
—> side effects - Platelet-rich plasma (PRP)
—> anti-inflammatory effect
—> lack level I evidence - Stem cells
—> lack level I evidence
- Surgical
- Arthroscopy
—> loose bodies, meniscal tear with locking symptoms in the knee
—> arthroscopic lavage / debridement
——> washout debris, synovial fluid and remove damaged cartilage / bone
——> ineffective / surgical placebo
- ***Realignment osteotomy
—> redistribute stress to normal part of the joint - ***Joint replacement
