L03 - Introduction to Degenerative Joint Disorders Flashcards by Benjamin Chan

Define OA?

■ progressive loss of articular cartilage

■ accompanied by attempted repair of the cartilage, remodelling and sclerosis of subchondral bone, formation of subchondral bone cyst and marginal osteophytes

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Epidemiology of OA?

common, age-related, heterogeneous

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Why can’t articular cartilage fully repair?

Articular cartilage is avascular, aneural, alymphatic

Relies on diffusion for nutrients… etc

does not have the capacity to repair structural damage

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What are the components of articular cartilage?

■ Chondrocytes
■ Water
■ Structural macromoleules:
– type II collagen (60 % of dry weight)
– Proteoglycans = protein core and one or more glycosaminoglycan (hyaluronic acid, chondroitin sulfate, keratan sulfate, dermatan sulfate) chains
– Non-collagenous proteins & glycoproteins

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Describe the interaction between the matrix and the chondrocytes in articular cartilage?

– Matrix protects chondrocytes from mechanical damage … transduce and transmits signals with loading …

– Chondrocytes degrade and synthesize matrix macromolecules … synthesize and release cytokines

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Compare the structural changes between normal aging articular cartilage and OA?

Aging = stable structure 
OA = progressive structural changes

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Compare between aging articular cartilage and OA: Water content?

Aging = Decrease water content

OA = Increase water content

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Compare between aging articular cartilage and OA: collagen structure?

Aging = Increase cross-linking between collagen

OA = Change in arrangement & size of collagen fibres + progressive loss of proteoglycans

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What are some causes of secondary OA?

Trauma - High-intensity-impact joint-loading**
Injury – ligament injury**
Infection – septic arthritis**
Hereditary – ochronosis
Endocrine – acromegaly, hypothyroidism

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Which parts of the body is affected by primary OA?

Hips & Knee

Distal interphalangeal joints of hands

Many Synovial joints

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What is found in the joints of the hands in primary OA?

Heberdon’s nodes in DIP

Bouchard’s nodes in PIP

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List some synovial joints that are affected in primary OA?

Mainly:
Hip and knee + DIP, PIP in hand

Others:
• carpometacarpal joint of thumb 
• metatarsophalangeal joint of the great toe 
• facet joints of the spine 
• elbows 
• shoudlers

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What causes OA?

Systemic factors that predispose to OA
\+
Local mechanical factors that dictate its distribution and severity 
\+/-
Various genetic abnormalities 
= 
Joint damage

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What are some systemic factors that predispose to OA?

Old  
Female 
Low Bone density 
Hormonal status - e.g. postmenopausal 
Nutrition and metabolic factors

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What are some Local mechanical factors that dictate the distribution and severity of OA?

– Joint deformity/malalignment
– Joint injury
– Muscle weakness
– Obesity

– Occupational factors
– Sports

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What are the 2 types of lower limb misalignment?

Genu valgum = knock knee

Genu varum = bow leg

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How do local mechanical factors affect the progression of OA?

Create uneven loading of the joints = exacerbate damage to joint = increase attempt to heal and worsening pathology

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Compare the prevalence of OA hip in Chinese and White ethnicities?

– 43 / 100,000 in Whites
– 1.3 / 100,000 in Chinese population

OA hip was rare in Hong Kong Chinese age > 50

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What is the EULAR guideline on clinical features of OA?

3 symptoms, 3 signs

– Persistent pain
– Limited morning stiffness
– Reduced function

– Crepitus*
– Restricted ROM
– Bony enlargement

Describe the clinical feature of pain due to OA?

Triphasic pain: increase when starts to walk, decrease after a while, increase again with long walk

What is the range of severity of OA pain?

Increasing severity:

• at rest • at night • need of pain killers • walking distance and walking aids • effect on daily activities, occupation, hobbies

Describe the clinical feature of stiffness due to OA?

Gelling after waking up or prolonged immobility
Effect on daily activities (i.e. cannot put on socks, cut toe nails, squat)
Limited passive ROM in physical exam

What causes crepitus in OA knee?

Grating, crackling or popping sounds and sensations experienced under the skin and joints

due to loss of articular cartilage that creates lots of friction

Describe grade 0 to grade 4 of Articular cartilage damage in OA?

– Grade 0: Normal cartilage

– Grade I: cartilage becomes soft and swells

– Grade II: partial-thickness defect with fibrillation (shredded appearance) or fissures (depressions)

– Grade III: increased amount of damage to the level of subchondral bone

– Grade IV: exposed subchondral bone, “eburnation” ( bone in contact with joint surface = smooth marble-like appearance)

What are the pathoanatomical features of OA?

■ Articular cartilage damage ■ Osteophyte formation ■ Subchondral sclerosis ■ Subcondral cysts

Osteophyte formation causes pain in patients with OA knee and forms due to aberrant growth of damaged bone. True or False?

False Osteophyte formation is attempted repair of loss of cartilage Formed to increase surface area of the bone and relieve pressure from loading of body weight Not a cause of pain in most patients

Explain why subchondral cysts occur in OA?

Loss of cartilage (bare bone) >> high pressure from joint pushes synovial fluid into subchondral area >> form cyst in bone where pressure is lower

What forces act on the hip when walking?

Weight of body part + forces created by muscle contraction 3 times body weight during single-legged stance

What increases the loading force on the knee joint in OA?

Varus malalignment and increased knee adduction movement

What is the loading force on the knee during walking?

3X Body Weight during level ground walking 4X Body Weight with stair walking 60-70% force on the medial side of knee

What increases the forces on the Patellofemoral joint surface in OA?

Increase deep knee bend due to abnormal gait Abnormal patellar height and abnormal tracking movement

What is the magnitude of forces on the patellofemoral joint surface when descending stairs?

2-3X Body Weight while descending stairs

What are the investigative tests for OA?

■ Imaging (common) – Plain radiographs – Magnetic resonance imaging ■ Blood tests (rare) ■ Joint aspiration (rare)

What is the classification used to assess Xray of OA hip or knee?

Kellgren Lawrence Classification

What are the grades in Kellgren Lawrence Classification?

Grade 0 = normal Grade 1 = Doubtful narrowing of joint space and possible osteophtic lipping Grade 2 = Definite osteophyte and possible narrowing of joint space Grade 3 = Moderate multiple osteophytes, definite narrowing of joint space + sclerosis Grade 4 = Large osteophytes, marked narrowing of joint space, severe sclerosis, definite deformity of bone ends

What are the pathological features of MRI in OA?

- Meniscal tear due to trauma and degeneration - Loose bodies (fragments of cartilage or bone that freely float inside the knee joint space) - Bakers cysts (fluid-filled cyst that causes a bulge and a feeling of tightness behind your knee)

What does increase in ESR AND CRP signify when investigating OA?

Normally degenerative OA = normal ESR and normal CRP Severe inflammatory cause = Increased ESR and CRP

What is the normal blood test result for OA?

Normal WBC Normal ESR and CRP Normal bone profiles (ions i.e. calcium, phosphate, alkaline phosphatase)

What is the normal joint fluid aspiration result for degenerative OA?

– Clear – Total cell count <1000/mm3 – Gram smear –ve & culture –ve – Crystals -ve

What is the normal joint fluid aspiration result for gouty OA?

Increased WBC | Increased urate crystals

What are some physical treatments and risk factor modifications for OA?

- Weight loss, walking aid - Muscle strengthening, ROM exercise, Muscle stretching, Aerobic exercises - Knee brace and shoe insoles

What are some pharmacological treatments for OA?

■ Acetaminophen ■ Non-steroidal anti-inflammatory drugs (NSAID) : Non-selective + COX-2-specific inhibitor ■ Topical agents ■ Others – Narcotic analgesics – Anticonvulsants – Antidepressants

What supplements can be taken for OA?

Glucosamine – Substrate for synthesis of proteoglycans

How does Hyaluronate intra-articular injections help OA?

Hyaluronate/ Glycosaminoglycan Injected to act as visco-supplementation: Supplement viscosity of joint fluid for lubrication & cushioning & Pain relief

What are the 4 intra-articular injections for OA?

■ Hyaluronate (common) ■ Steroid (common) ■ Platelet rich plasma (PRP) ■ Stem cells

What surgery can be done for OA?

1) Arthroscopy – Loose bodies, meniscal tear with locking symptoms in the knee >> Arthroscopic “lavage” or “debridement”: washout debris, synovial fluid and remove damaged cartilage or bone 2) Realignment osteotomy >> Redistribute stress to normal part of the joint 3) Joint replacement (for end stage OA)