Osteoarthritis and Reactive Arthritis

Question 1

Reactive arthritis

Answer 1

• sterile inflammation in joints following infection especially urogenital (Chlamydia) and gastrointestinal (Salmonella, Shigella=food poisoning) infections
• may be first manifestation of HIV or Hep C
• commonly presents in young adults with genetic predisposition (HLA-B27) and environmental triggers (salmonella infection)
• symptoms follow 1-4 weeks after infection (could be mild infection)
• distinct from direct infection in joints (septic arthritis)=reactive is an immune reaction to previous infection
• part of seronegative spondyloarthropathies (family of rheumatological disorders)=no rheumatoid factor present

Important extra-articular manifestations include:

• enthesopathy (relates to ligament/tendon attachment to bone)
• skin inflammation
• eye inflammation (uveitis)

Question 2

Musculoskeletal symptoms of reactive arthritis

Answer 2

-no biomedical test as seronegative
ARTHRITIS
-largely asymmetrical oligoarthritis (<5 joints affected)
-lower limbs typically affected
ENTHESITIS= entheses inflammation
-heel pain (achilles tendonitis)
-swollen fingers (dactylitis)=soft on palpation
-painful feet (metatarsalgia due to plantar fascilitis)
SPONDYLITIS=spinal inflammation
-sacroiliitis (sacro-iliac joint inflammation)
-spondylitis (spinal inflammation)

Question 3

Extra-articular features of reactive arthritis

Answer 3

OCULAR
-sterile conjunctivitis
GENITO-URINARY
-sterile urethritis (mainfests as pain during urination)
SKIN
-circinate balanitis
-keratoderma blennorrhagicum

Question 4

Original description of reactive arthritis

Answer 4

Triad of arthritis, urethritis and conjunctivitis following infectious dysentery (Reiter’s syndrome)

Question 5

Reactive arthritis features

Answer 5

• more common in males than females (manifest immune response to infection)
• 20 to 40 years old
• arthritis=asymmetrical, oligoarticular, large joints
• enthesopathy present
• spondylitis present
• urethritis present
• skin involvement in form of keratoderma blennorrhagicum and circinate balanitis
• no rheumatoid factor
• HLA-B27 association

Question 6

Reactive arthritis diagnosis

Answer 6

• primarily clinical diagnosis/presentation

- investigations to exclude other arthritis causes (eg: septic arthritis)

Question 7

Important investigations for reactive arthritis

Answer 7

MICROBIOLOGY
-microbial cultures (blood, throat, urine, stool, urethral, cervical)
-serology (eg: HIV, Hep C)
IMMUNOLOGY
-rheumatoid factor 
-HLA-B27
SYNOVIAL FLUID EXAMINATION
-used especially if only single joint affected to rule out septic arthritis (fluid aspirated from space around joint and tested eg: gram stain)

Question 8

Septic arthritis vs reactive arthritis

Answer 8

• synovial fluid culture positive in septic but negative in reactive
• antibiotic therapy positive in septic but negative in reactive
• joint lavage for septic (for large joints) but not for reactive

Question 9

Reactive arthritis treatment

Answer 9

• Complete resolution occurs within 2-6 months in majority of patients
• no role for antibiotics

Articular:
-NSAIDS
-intra-articular corticosteroid therapy
Extra-articular:
-symptomatic therapy as typically self-limiting (eg: topical steroids and keratolytic agents in keratoderma)
Refractory disease (non-responsive to treatment):
-oral glucocorticoids
-steroid-sparing agents (DMARDs eg: sulfasalazine)

Question 10

Osteoarthritis

Answer 10

• associated with the elderly= ‘wear and tear’ arthritis of old age resulting in bone on bone
• chronic, slowly progressive disorder due to failure of articular cartilage that typically affects joints of the hand (DIP, PMP, CMC=not MCP), the spine and weight-bearing joints
• not inflammatory or autoimmune condition=hard bony overgrowth on palpation

Question 11

Commonly affected joints in osteoarthritis

Answer 11

JOINTS OF THE HAND
-distal interphalangeal joints (DIP)
-proximal interphalangeal joints (PIP)
-first carpometacarpal joint (CMC)=very common and evident on pincer grip
SPINE
WEIGHT-BEARING JOINTS OF LOWER LIMBS
-knees and hips
-first metatarsophalangeal joint

Question 12

Heberden’s nodes

Answer 12

-osteophytes at DIP joints

Question 13

Bouchard’s nodes

Answer 13

-osteophytes at PIP joints

Question 14

Osteoarthritis can be associated with:

Answer 14

JOINT PAIN
-typically worse with activity and better with rest
JOINT CREPITUS
-creaking, cracking grinding sound on moving affected joint
JOINT INSTABILITY
JOINT ENLARGEMENT
eg: Heberden’s nodes
JOINT STIFFNESS AFTER IMMOBILITY
-often described as gelling
-contributed to muscle atrophy surrounding joint
-may be element of morning stiffness but lasts <30 mins
LIMITATION OF MOTION

Question 15

Radiographic features of osteoarthritis

Answer 15

• joint space narrowing to give bone bone appearance
• subchondral bony sclerosis=hardening of bone on subchondral surface (increased area of whitening)
• osteophytes=bony projections associated with cartilage degeneration
• subchondral cysts

Question 16

Radiographic changes: rheumatoid arthritis vs osteoarthritis

Answer 16

• Joint space narrowing indicates articular cartilage loss and occurs in both osteo (primary abnormality) and in rheumatoid (secondary damage due to synovitis)
• osteo has subchondral sclerosis but rheumatoid does not
• osteo has osteophytes but rheumatoid does not
• rheumatoid has osteopenia but osteo does not (juxta-articular osteopenia common early radiographic sign in inflammatory arthritis of any cause=darker area on x-ray)
• rheumatoid has bony erosions but osteo does not (initially at joint margins where synovium in direct contact with bone)

Question 17

Osteoarthritis pathogenesis

Answer 17

-there is a defective and irreversible articular cartilage and damage to underlying bone

Development due to (and/or):

• excessive loading on joints
• abnormal joint components

Question 18

Synovial joint

Answer 18

SYNOVIUM
-1-3 cells deep
-contains type A synoviocytes (phagocytic) and type B synoviocytes (fibroblast like) which produces hyaluronic acid
SYNOVIAL FLUID
-hyaluronic acid-rich viscous fluid
ARTICULAR CARTILAGE
-contains type II collagen and proteoglycan (mainly aggrecan=retainss water to give strength under compression as shock absorber)

Question 19

Properties of articular cartilage

Answer 19

-weight-bearing properties depend on intact collagen scaffold and high aggrecan content

Question 20

ECM proteoglycans

Answer 20

• proteoglycans=glycoproteins containing one or more sulphated GAG (glycosaminoglycan) chains
• GAGs are repeating polymers of disaccharides eg: chondroitin sulphate, heparan sulphate, keratan sulphate, dermatan sulphate and heparin
• aggrecan=major proteoglycan in articular cartilage
• hyaluronic acid=only non-sulphated GAG and important synovial fluid component to maintain synovial fluid viscosity (disaccharides of glucuronic acid and N-acetyl glucosamine)

Proteoglycan examples include:

• INTRACELLULAR (serglycin)
• CELL SURFACE ASSOCIATED (betaglycan)
• SECRETED INTO ECM (aggrecan, decorin etc)

Question 21

Cartilage changes in osteoarthritis

Answer 21

• reduced proteoglycan
• reduced collagen
• chondrocyte changes (eg: apoptosis)

Question 22

Bone changes in osteoarthitis

Answer 22

CHANGES IN SUB-ARTICULAR BONE
NEW BONE
-proliferation of superficial osteoblasts results in sclerotic bone production
-focal stress of sclerotic bone can result in focal superficial necrosis
FORMATION AT JOINT MARGINS (BONE SPURS)
-examination can detect osteophytes clinically
-Heberden’s nodes and Bouchard’s nodes

Question 23

Osteoarthritis management

Answer 23

• education
• physical therapy (physio, hydrotherapy)=prevent muscle atrophy which would lead to joint instability
• occupational therapy
• weight loss where appropriate (reduce load on joint)
• exercise
• analgesia (paracetamol, NSAIDs, intra-articular corticosteroid injections)=symptomatic Tx
• joint replacement