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Joint Guard

A clinician's decision aid for suspected joint-replacement infection — score the criteria with lab thresholds, then compare the treatment pathways on time and success.

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The clinical picture

Time since surgery

Acute = early / short symptom duration (typically within ~4–6 weeks of surgery or of a hematogenous seed). Chronic = late or long-standing. Timing routes which pathways are surfaced first.

acutechronic

CRP (mg/L)

C-reactive protein, a marker of inflammation. Counts as a minor criterion when above 10 mg/L. One elevated marker alone is suggestive, not definitive.

ESR (mm/hr)

Erythrocyte sedimentation rate, a slower inflammation marker. Counts as a minor criterion above 30 mm/hr.

Elevated synovial WBC / PMN%minor

A raised synovial white-cell count or neutrophil percentage from joint aspiration — a minor criterion.

Sinus tract communicating with the jointmajor

A draining tract connecting skin to the prosthesis. This is a major criterion — it meets the PJI definition on its own.

Two or more positive periprosthetic culturesmajor

The same organism from two or more separate samples. A major criterion — meets the definition on its own.

Likelihood
?
A major criterion (sinus tract or 2+ positive cultures) meets the PJI definition on its own → Criteria met. Otherwise the three minor criteria (CRP↑, ESR↑, synovial↑) accumulate: 3 → Probable, 1–2 → Possible, 0 → Unlikely. Educational — the clinician decides.

INSUFFICIENT DATA

Enter CRP and ESR values to score the minor criteria — gather more before deciding.

Major criterion ? Either a sinus tract or two+ positive cultures. Present = the PJI definition is met.: Not met
Minor criteria ? Count of CRP↑, ESR↑, and synovial↑ (0–3). Three is strongly suggestive.: 0 / 3
Presentation: acute

Suggested next steps

Enter a CRP value (mg/L).
Enter an ESR value (mm/hr).

What would change this

The nearest findings that would raise the concern level — a quick check of what you may be one result away from. It never lowers the level or overrides your judgment.

Enter CRP and ESR to score the minor criteria.

Compare pathways →

Educational decision-support only — not a substitute for clinical judgment. Data stays on this device (autosaved locally); nothing is uploaded.

Integrity checkde-identified fingerprint of the entered criteria

joint-guard.audit

$ level  INSUFFICIENT DATA
$ major  false   minor 0/3
sha256: …
status: computed on-device · no PHI stored

Ask AI

AI can be wrong. Not medical, legal, or financial advice.

Try an example

The clinical picture

Likelihood?A major criterion (sinus tract or 2+ positive cultures) meets the PJI definition on its own → Criteria met. Otherwise the three minor criteria (CRP↑, ESR↑, synovial↑) accumulate: 3 → Probable, 1–2 → Possible, 0 → Unlikely. Educational — the clinician decides.

Integrity checkde-identified fingerprint of the entered criteria

Ask AI

Likelihood
?
A major criterion (sinus tract or 2+ positive cultures) meets the PJI definition on its own → Criteria met. Otherwise the three minor criteria (CRP↑, ESR↑, synovial↑) accumulate: 3 → Probable, 1–2 → Possible, 0 → Unlikely. Educational — the clinician decides.