MSU Crystal-Triggered Neutrophil Influx
Urate crystals precipitate in the joint and recruit neutrophils fast.
- >6.8 mg/dL: Serum urate threshold (saturation point)
- Needle-like: Crystal shape (monosodium urate)
- 2–6 h: Neutrophil influx onset (from first symptom)
- 12–24 h: Peak flare intensity (typical timing)
Crystal deposition
Cooling joints let urate crystallize out of supersaturated synovial fluid.
Innate immune recognition
Resident macrophages sense crystals via NLRP3 and release IL-1β.
Neutrophil recruitment
Chemokines draw circulating neutrophils rapidly into the joint space.
Choosing Colchicine, NSAID, or Glucocorticoid
Drug choice depends heavily on how long symptoms have lasted.
- <36 h: Colchicine window (best efficacy early)
- <48–72 h: NSAID window (broad effective range)
- Any time: Glucocorticoid window (reliable regardless of delay)
- Steroid preferred: Renal-impaired option (avoids NSAID/colchicine risk)
Timing drives efficacy
Colchicine loses potency the longer treatment is delayed.
Comorbidity constraints
Kidney disease often rules out NSAIDs and colchicine dosing.
Steroid flexibility
Glucocorticoids work well even when the flare is late.
Suppressing the Inflammatory Cascade
The chosen drug interrupts crystal-driven inflammatory signaling.
- Indirect: IL-1β blockade (via NLRP3 pathway)
- Reduced: Neutrophil chemotaxis (colchicine mechanism)
- Blocked: Prostaglandin synthesis (NSAID mechanism)
- Suppressed: Gene transcription (glucocorticoid mechanism)
Colchicine mechanism
Colchicine disrupts microtubules, halting neutrophil movement into the joint.
NSAID mechanism
NSAIDs block COX enzymes, cutting prostaglandin-driven pain and swelling.
Glucocorticoid mechanism
Steroids broadly suppress inflammatory gene expression within hours.
Pain and Swelling Resolution Over Time
Pain and swelling decline steadily once treatment takes hold.
- ~50%: Pain reduction (24h) (with early treatment)
- ~24–48 h: Swelling half-life (treated flare)
- 7–14 d: Untreated resolution (natural course)
- 2–5 d: Treated resolution (typical range)
Pain curve
Pain scores fall fastest in the first two treated days.
Swelling lag
Joint swelling resolves slightly slower than reported pain.
Dose-response
Earlier treatment consistently shortens the overall recovery curve.
Flare Resolved vs Delayed-Treatment Course
Early treatment resolves flares far faster than delayed care.
- ~48 h: Treated within 12h (to resolution)
- ~5–7 d: Treated after 48h (to resolution)
- 7–14 d: Untreated flare (natural course)
- ~60%: Recurrence risk (within 1 yr, untreated hyperuricemia)
Fast-track resolution
Prompt treatment shortens flares to roughly two days.
Delayed course
Late treatment still helps but recovery drags on.
Long-term control
Urate-lowering therapy afterward prevents future recurrent flares.