Unifying Concepts

Diagnostic Criteria of Periprosthetic Joint Infection (PJI)

Periprosthetic joint infection (PJI) is a serious and potentially devastating complication that can occur after joint replacement surgery, such as hip or knee replacement. It refers to the presence of an infection in or around the artificial joint (prosthesis) that has been implanted during the surgical procedure.

Musculoskeletal Infection Society (MSIS) criteria for diagnosis of prosthetic joint infection

Major Criteria*

  • Communicating sinus tract to joint or prosthesis
  • Isolated organism in two different tissue/fluid cultures

Minor Criteria**

  • Elevated ESR/CRP
  • Elevated synovial leukocyte count
  • Elevated synovial PMN%
  • Purulent material
  • Isolated organism in one tissue/fluid culture
  • >5 neutrophils per hpf in 5 hpf histologic tissue analysis ✕400 magnification

*1 criterion is needed to establish diagnosis of prosthetic joint infection
**4 out of 6 minor criteria are needed to establish diagnosis of prosthetic joint infection.
CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; hpf, high-power field; PMN%, polymorphonuclear neutrophil percentage


New scoring-based definition

Major criteria (at least one of the following)
Two positive cultures of the organism Infected
Sinus tract with evidence of communication to the joint or visualization of the prosthesis
Preoperative diagnosis Minor criteria Score Decision
Elevated CRP or D-Dimcr 2 ≥6 Infected
2–5 Possibly infecteda
0–1 Not infected
Elevated ESR 1
Elevated synovial WBC or LE 3
Positive alpha-defensin 3
Elevated synovial PMN 2
Elevated synovial CRP 1
Intraoperative Inconclusive pre-op score or dry tap Score Decision
Preoperative score ≥6 Infected
4–5 Inconclusiveb
≤3 Not infected
Positive histology 3
Positive purulence 3
Single positive culture 2

a For patients with inconclusive minor criteria, operative criteria can also be used to fulfil the definition for PJI
b Consider further molecular diagnostics such as next-generation sequencing



  1. Patel R. Periprosthetic Joint Infection. N Engl J Med. 2023 Jan 19;388(3):251-262. [Medline]
  2. Tripathi S, Tarabichi S, Parvizi J, Rajgopal A. Current relevance of biomarkers in diagnosis of periprosthetic joint infection: an update. Arthroplasty. 2023 Aug 1;5(1):41. [Medline]


Created Aug 31, 2023.

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