Lower Limb Arthritis Flashcards
What is gout?
Inflammatory arthritis, arising from hyperuricemia and deposition of monosodium urate crystals in the joints
What causes hyperuricemia?
- Excess purines (high purine diet, enzymatic defects)
- Increased catabolism of nucleic acids due to high cell turnover (infections, cancer)
- Decreased renal excretion of uric acid
What are risk factors for gout?
- Male
- Old
- Diabetes, Hyperlipidemia, Hypertension
- Hyperuricemia-inducing drugs (thiazide/loop diuretics, ciclosporin, aspirin)
What is the pathophysiology of gouty arthritis?
- Hyperuricemia > precipitation of MSU crystals in bloodstream > deposition in joints and surrounding tissues
- Causes inflammation, releasing IL-1 to recruit neutrophils
- Neutrophils release inflammatory mediators to attract other phagocytes, and attempt to phagocytose crystals
- Phagocytes’ lysosome membranes are damaged by crystals, releasing hydrolytic enzyme content
- Manifests as severe, sudden inflammatory attack, esp. at MTP of big toe
- Over time, recurrent crystal deposition can cause firm yellow nodules (tophi) around joints and ears
S/S of gout?
- Needle-like crystals in joint aspirate
- Sudden, severe inflammatory arthritis attacks (esp. at night)
- Limited ROM due to pain
- Tophi
- Advanced, LT gout can cause joint destruction + hypertrophy (bony sclerosis), leading to overhanging edges in the joint
Treatment of gout?
Uric acid-lowering therapies
Who are uric acid-lowering therapies indicated for?
- > 65 y/o
- CKD
- > 5 gouty attacks / year
- Tophi
What is pseudogout?
Gout-like inflammatory arthritis, arising from deposition of calcium pyrophosphate dihydrate crystals in the joints. aka Chondrocalcinosis
What causes pseudogout?
Idiopathic; associated with trauma, hyperparathyroidism, and haemochromatosis
S/S of pseudogout?
- Usually asymptomatic, or similar to gout
- Under polarised light, joint aspirate reveals strongly birefringent, rhomboid-shaped crystals
How to differentiate between gout and pseudogout?
Joint aspirate crystals
What is septic arthritis?
Suppurative inflammatory arthritis, caused by infectious agent
What usually causes septic arthritis?
- Streps, S. aureus, Pseudomonas, GN rods (e.g. Gonococcus)
- Spread via blood; direct inoculation; spread from adjacent soft tissue infections / osteomyelitis
S/S of septic arthritis?
- Red, hot, swollen joint
- Rapid onset joint pain, worsened with movement
- Purulent fluid in joint aspirate
- Unilateral hip / knee joints affected
Unique S/S of gonococcal septic arthritis?
- Septic emboli
- STD / UTI symptoms, e.g. painful micturition
- GN rods in joint aspirate
Describe treatment of gonococcal septic arthritis.
IV/IM ceftriaxone
Unique S/S of S. agalactiae septic arthritis?
- Gp B Streps in joint aspirate
- Associated with raw fish consumption
What is osteomyelitis?
Bone infection involving cortex, medulla, and periosteum, usually caused by S. aureus
What usually causes osteomyelitis?
- S. aureus
- Spread via blood, direct inoculation, or from adjacent soft tissue infections
How do you detect osteomyelitis?
- MRI
- Tissue culture / Biopsy
How do you treat osteomyelitis?
Targeted, specific antibiotic therapy
What is suppurative osteomyelitis?
Acute / Acute-on-chronic pyogenic osteomyelitis
What is the pathogenesis of suppurative osteomyelitis?
- Infection localised in cortex, forming small abscess
- Abscess enlarges, and grows into sub-periosteal space
- Abscess may escape from bone via sinus tracts
- Abscess may undergo necrosis
What are the possible sequelae of suppurative osteomyelitis?
- Healing and resolution
- Subacute / Chronic suppurative osteomyelitis
- Abscess, necrosis
- Pathological fractures / deformities (proliferative periostitis, involucrum)
- Sinus tract formation in skin and soft tissue
- Secondary amyloidosis
- Malignant transformation to osteosarcoma (bone) / squamous cell carcinoma (sinus tract)
What is proliferative periostitis?
- Extensive new bone formation, especially in children’s jaws (Garre’s sclerosing osteomyelitis)
- Causes irritation, trauma, and dental infection