MSIS Criteria

MSIS Criteria: Major and minor prosthetic joint infection diagnostic features.

Clinical Factors

Assessment Tier

Low

Score 0

Selected features provide limited support for PJI.

Guidelines & Evidence

Clinical Details

Section 1

When to Use

Use during early bedside triage when infection severity or treatment escalation is uncertain.

Support clinician judgement with a structured review of the highest-yield risk factors.

Standardise communication between admitting, ID, ICU, and pharmacy teams.

Section 2

Formula & Logic

Scoring Logic

Sinus tract to prosthesis (+3)

Two positive cultures with same organism (+3)

Elevated synovial WBC/PMN (+2)

Elevated ESR or CRP (+1)

Purulence around prosthesis (+2)

Positive histology / single culture (+1)

Section 3

Next Steps

Clinical Actions

Interpret the result together with source control, microbiology, host factors, and trajectory.

Escalate imaging, cultures, or specialist review when the tool lands in a high-risk tier.

Reassess dynamically if the patient deteriorates or new microbiology becomes available.

Section 4

Pearls/Pitfalls

Important Caveat

This tool supports structured infectious-disease decision making but does not replace clinician judgement or local guideline pathways.

Section 5

Evidence Appraisal

Evidence Base

This OpiCalc infectious-disease entry reflects commonly used guideline criteria and bedside risk features used in contemporary clinical practice.

Last Comprehensive Review: 2026

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