Osteoarthritis and Reactive Arthritis Flashcards
What is reactive arthritis?
sterile inflammation in joints following infection, especially urogenital (e.g. Chlamydia trachomatis) and gastrointestinal (e.g. Salmonella, Shigella, Campylobacter infections) infections
may be the first manifestation of HIV or hepatitis C infection
commonly affects young adults with genetic predisposition and environmental trigger e.g genetic predisposition could be HLA-B27, and environmental trigger could be salmonella infection
- distinct from infection in joints (septic arthritis)
What areas are affected by reactive arthritis?
Joints AND extra-articular areas are affected
e. g Enthesopathy (overlap between reactive arthritis and seronegative spondyloarthropathies)
- Skin inflammation
- Eye inflammation
What are the musculoskeletal symptoms of reactive arthritis?
ARTHRITIS: asymmetrical, oligoarthritis (<5 joints), lower limbs are typically affected
ENTHESITIS:
- Heel pain (Achilles tendonitis)
- Swollen fingers (dactylitis)
- Painful feet (metatarsalgia due to plantar fasciitis)
SPONDYLITIS: predilection for spinal inflammation:
- Sacroiliitis (inflammation of the sacro-iliac joints)
- Spondylitis (inflammation of the spine)
What are some differences between rheumatoid arthritis and reactive arthritis?
reactive:
- asymmetrical
- M>F sex ratio
- 20-40yrs
- oligoarticular
- enthesopathy, spondylitis, urethritis
- no rheumatoid factor
- HLA-B27
rheumatoid:
- symmetrical
- no thoracic and lumbar involvement (no synovial joints)
- F>M
- all ages
- polyarticular
- no enthesopathy, spondylitis or urethritis
- rheumatoid factor
- HLA-DR4
What are the extra-articular features of reactive arthritis?
- Ocular: sterile conjunctivitis
- Genito-urinary: sterile urethritis
- Skin: circinate balanitis AND psoriasis-like rash on hands and feet
How is the diagnosis for reactive arthritis established?
Clinical diagnosis
- Investigations to exclude other causes of arthritis e.g. septic arthritis
Microbiological analysis:
- Microbial cultures – blood, throat, urine, stool, urethral, cervical
- Serology e.g. HIV, hepatitis C
Immunological tests:
- Rheumatoid factor should be negative in reactive arthritis
- (HLA-B27 – not particularly useful in this setting, because 9% of the population are positive)
Synovial fluid examination:
- Especially if only single joint affected
What are some differences between septic arthritis and reactive arthritis?
septic:
- positive synovial fluid culture
- antibiotic therapy
- joint lavage for large joints
reactive:
- sterile synovial fluid culture
- no antibiotic therapy or joint lavage
How is reactive arthritis treated?
- majority of patients, complete resolution occurs within 2-6 months. In the mean time, we want to REDUCE INFLAMMATION and CONTROL PAIN.
Articular:
- NSAIDs
- intra-articular corticosteroid therapy
Extra-articular:
- typically self-limiting, hence symptomatic therapy e.g topical steroids & keratolytic agents in keratoderma
Refractory disease:
- Oral glucocorticoids
- Steroid-sparing agents e.g. sulphasalazine
What is osteoarthritis?
Chronic slowly progressive disorder, primarily due to failure of articular cartilage that typically affecting joints of the hand (especially those involved in pinch grip - DIP, PIP, 1ST CMC), spine and weight-bearing joints (hips and knees and 1ST MTP)
What nodes do you get in osteoarthritis?
HEBERDEN’S NODES: bony, prominent swelling around the distal interphalangeal joints
BOUCHARD’S NODES: bony swellings around the proximal interphalangeal joints
What is osteoarthritis associated with?
- Joint pain: worse with activity, better with rest (loss of articular cartilage -> mechanical failure of joints)
- Joint crepitus: creaking, cracking, grinding sound on moving affected joint
- Joint instability
- Joint enlargement e.g. Heberden’s nodes
- Joint stiffness after immobility (‘gelling’)
- Limitation of motion
What are the radiographic features of osteoarthritis?
- Joint space narrowing
- Subchondral bony sclerosis (underlying bone reacting to damaged articular cartilage)
- Osteophytes (Heberden’s and Bouchard’s nodes)
- Subchondral cysts
Compare the radiographic changes in rheumatoid and osteoarthritis?
rheumatoid:
- joint sparing narrowing
- no subchondrial sclerosis
- no osteophyles
- osteopenia
- bony erosions
osteoarthritis:
- joint sparing narrowing
- subchondrial sclerosis
- osteophyles
- no osteopenia
- no bony erosions
What causes osteoarthritis?
- Excessive loading on the joints
- Abnormal joint components
- very multifactorial condition. There are some rare metabolic and endocrine factors
Describe the structure of articular cartilage?
What causes articular cartilage to break down?
- avascular and an aneural structure
- The collagen is type II.
- large, proteoglycan monomers. The key proteoglycan in articular cartilage is aggrecan. It is HUGE (2-3 million kDa).
The aggrecan contains glycosaminoglycan side chains (e.g. chondroitin sulphate, keratin sulphate) - negatively charged s attracts water keeping the cartilage hydrated.
When this is lost, articular cartilage becomes fragile and begins to break down.
What are proteoglycans?
glycoproteins containing one or more sulphated glycosaminoglycan (GAG) chains
What are the different GAGs?
- repeating polymers of disaccharides
include:
- Chondroitin sulphate (disaccharides are: glucuronic acid and N-acetyl galactosamine)
- Heparan sulphate
- Keratan sulphate (disaccharides are: galactose and N-acetyl glucosamine)
- Dermatan sulphate
- Heparin
- Hyaluronic acid is the only non-sulphated GAG and is major component of synovial fluid
What are some examples of proteoglycans?
- Intracellular: serglycin
- Cell surface associated: betaglycan, syndecan
- Secreted into ECM: aggrecan, decorin, fibromodulin, lumican, biglycan
What are the cartilage changes in osteoarthritis?
- Reduced proteoglycan
- Reduced collagen
- Chondrocyte changes e.g. apoptosis
- CHANGES ARE OFTEN LOCALISED
What are the bone changes in osteoarthritis (once cartilage is damaged)?
Changes in denuded sub-articular bone:
- Proliferation of superficial osteoblasts results in production of sclerotic bone e.g. subchondral sclerosis
- Focal stress on sclerotic bone can result in focal superficial necrosis
What are osteophytes?
New bone formation at the joint margins
Sometimes you can detect osteophytes clinically (‘at the bedside’) and these have names
- at the distal inter-phalangeal joints: ‘Heberden’s nodes’
- at the proximal inter-phalangeal joints: ‘Bouchard’s nodes
How is osteoarthritis managed?
- Education
- Physical therapy – physiotherapy, hydrotherapy (optimizing physical strength of patient)
- Occupational therapy
- Weight loss where appropriate
- Exercise
- Analgesia
> Paracetamol
> Non-steroidal anti-inflammatory agents
> Intra-articular corticosteroid injection - Joint replacement if it comes to it – this has been a MAJOR success
What therapeutic approaches for osteoarthritis are not approved in the UK?
Glucosamine and chondroitin sulphate – commonly taken
- Dietary supplementation commonly taken by patients
- Some studies suggesting improvement in pain (may be a placebo effect)
- NO CLEAR EVIDENCE THAT ORAL INTAKE ALTERS ARTICUALR CARTILAGE COMPOSITION
Intra-articular injections of hyaluronic acid
- Hyaluronic acid to increase lubrication (visco-supplementation)
- Only used in the knee joint and still experimental
- Not recommended by NICE but practiced a lot in private medicine
