Osteoarthritis and Reactive Arthritis Flashcards
Reactive arthritis
- 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)
Musculoskeletal symptoms of reactive arthritis
-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)
Extra-articular features of reactive arthritis
OCULAR -sterile conjunctivitis GENITO-URINARY -sterile urethritis (mainfests as pain during urination) SKIN -circinate balanitis -keratoderma blennorrhagicum
Original description of reactive arthritis
Triad of arthritis, urethritis and conjunctivitis following infectious dysentery (Reiter’s syndrome)
Reactive arthritis features
- 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
Reactive arthritis diagnosis
- primarily clinical diagnosis/presentation
- investigations to exclude other arthritis causes (eg: septic arthritis)
Important investigations for reactive arthritis
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)
Septic arthritis vs reactive arthritis
- 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
Reactive arthritis treatment
- 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)
Osteoarthritis
- 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
Commonly affected joints in osteoarthritis
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
Heberden’s nodes
-osteophytes at DIP joints
Bouchard’s nodes
-osteophytes at PIP joints
Osteoarthritis can be associated with:
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
Radiographic features of osteoarthritis
- 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
Radiographic changes: rheumatoid arthritis vs osteoarthritis
- 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)
Osteoarthritis pathogenesis
-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
Synovial joint
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)
Properties of articular cartilage
-weight-bearing properties depend on intact collagen scaffold and high aggrecan content
ECM proteoglycans
- 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)
Cartilage changes in osteoarthritis
- reduced proteoglycan
- reduced collagen
- chondrocyte changes (eg: apoptosis)
Bone changes in osteoarthitis
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
Osteoarthritis management
- 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
