6. Osteoarthritis and reactive arthritis

Question 1

What is reactive arthritis?

Answer 1

• Sterile inflammation in joints

* Following infection, especially urogenital (e.g. Chlamydia trachomatis) and GI (e.g. Shigella)

Question 2

What are the important extra-articular manifestations of reactive arthritis?

Answer 2

• Enthesopathy (overlap between ReA and seronegative spondyloarthropathies)
• Skin inflammation e.g. circinate balanitis and psoriasis-like rash on hands and feet
• Eye inflammation e.g. sterile conjuctivitis
• Genti-urinary inflammation e.g. sterile urethritis

Question 3

What serious infections can ReA be the first manifestation of?

Answer 3

HIV or hepatitis C

Question 4

What people does ReA commonly affect?

Answer 4

• Young adults with genetic predisposition and environmental trigger
• e.g. HLA-B27 or salmonella infection

Question 5

When do ReA symptoms appear following infection?

Answer 5

1-4 weeks after infection

Question 6

Are the joints infected in ReA?

Answer 6

No, this is septic arthritis

Question 7

Which MHC molecule is strongly associated with ankylosing spondylitis susceptibility and ReA?

Answer 7

Class I MHC - HLA-B27

Question 8

Describe the musculoskeletal symptoms of ReA (arthritis, enthesitis and spondylitis)

Answer 8

Arthritis
• Asymmetrical
• Oligoarthritis (<5 joints)
• Lower limbs typically affected

Enthesitis
• Heel pain (achilles tendonitis)
• Swollen fingers (dactylitis)
• Painful feet (metatarsalgia due to plantar fasciitis)

Spondylitis
• Spondylitis (inflammation of the spine)
• Sacroiliitis (inflammation of the sacro-iliac joints)

Question 9

How is the diagnosis for ReA established?

Answer 9

Microbiological analysis
• Cultures - blood, throat etc.
• Serology e.g. HIV, hep C

Immunological tests
• Rheumatoid factor should be negative
• HLA-B7 (only 9% are positive though, so not very useful)

Synovial fluid examination
• Especially if only single joint affected
• Fluid culture should be sterile (antibiotic therapy not necessary)

Question 10

How is ReA treated?

Answer 10

• Articular - NSAIDs, intra-articular corticosteroid therapy
• Extra-articular - symptomatic therapy e.g. topical steroids + keratolytic agents
• Refractory (stubborn) disease - oral glucocorticoids, steroid-sparing agents

Question 11

What is osteoarthritis?

Answer 11

• Chronic slowly progressive disorder
• Primarily due to failure of articular cartilage
• Typically affects the joints of the hand, spine and weight-bearing joints (hips and knees)

Question 12

Which joints of the hand does OA affect?

Answer 12

• Distal interphalangeal joints (DIP)
• Proximal interphalangeal joints (PIP)
• First carpometacarpal joint (CMC)

Question 13

Which joint in the feet does OA mainly affect?

Answer 13

First metatarsophalangeal joint

Question 14

Which joints affected in OA are normally spared in RA?

Answer 14

DIP joints

Question 15

What are Heberden’s nodes and Bouchard’s nodes?

Answer 15

• Heberden’s nodes - bony, prominent swelling around the DIP joints
• Bouchard’s nodes - bony swellings around the PIP joints

(both types of osteophytes)

Question 16

How does joint pain in OA change with activity and rest?

Answer 16

• Worse with activity

* Better with rest

Question 17

What is joint crepitus?

Answer 17

Creaking, cracking, grinding sound on moving affected joint

Question 18

How is stability, size and mobility of joints affected in OA?

Answer 18

• Joint instability
• Joint englargement
• Joint stiffness - limitation of motion

Question 19

Describe the radiographic features of osteoarthritis

Answer 19

• Joint space narrowing (loss of cartilage)
• Subchondral bony sclerosis (underlying bone reacting to damaged cartilage)
• Osteophytes
• Subchondral cysts

Question 20

If the defective damage to the articular cartilage in OA reversible?

Answer 20

No

Question 21

Is articular cartilage vascular or neural?

Answer 21

No - it is an avascular and aneural structure

Question 22

What side chains does aggrecan contain and how does it attract water?

Answer 22

• Glycosaminoglycan side chains e.g. chondroitin sulphate, keratin sulphate
• Negative charge attracts water, keeping it hydrated

Question 23

What are proteoglycans?

Answer 23

Glycoproteins containing one or more sulphated glycosaminoglycan (GAG) chains

Question 24

What are glycosaminoglycans (GAGs)?

Answer 24

Repeating polymers of disaccharides

Question 25

What is the only non-sulphated GAG?

Answer 25

Hyaluronic acid

Question 26

Describe the cartilage changes in OA

Answer 26

• Reduced proteoglycan (aggrecan is the major one)
• Reduce collagen (type II)
• Chondrocyte changes e.g. apoptosis

Question 27

Describe the bone changes in OA

Answer 27

• Proliferation of superficial osteoblasts => production of sclerotic bone
• Focal stress on sclerotic bone => focal superficial necrosis

Question 28

What therapeutic approaches to OA are not approved/recommended in the UK?

Answer 28

• Glycosamine and chondroitin sulphate - dietary supplementation (no clear evidence)
• Intra-articular injections of hyaluronic acid - not recommended by NICE but still practised in private medicine

Question 29

What disease modifying osteoarthritis drugs (DMOAD) can be used for OA?

Answer 29

There are none - maybe aggrecanase/cytokine inhibitors in the future?