Preoperative Thrombocytopenia Increases In-Hospital Burden but Not Postoperative Adverse Events After Total Knee Arthroplasty

Background/Objectives: Thrombocytopenia increases bleeding tendency and may complicate perioperative management in total knee arthroplasty (TKA), yet data on both in-hospital burden and post-discharge adverse events are limited. This study evaluated the association between preoperative platelet count and outcomes after primary TKA. Methods: In total, 3474 primary TKAs performed for osteoarthritis at a single institution (2008–2023) were retrospectively reviewed. Patients were classified as Normal, Mild, Moderate, or Severe by preoperative platelet count; the Severe group (N = 6) was excluded from comparative analyses and reported descriptively. Inverse probability of treatment weighting (IPTW) balanced baseline covariates. In-hospital outcomes were red blood cell (RBC) transfusion, intensive care unit (ICU) admission, and length of stay; follow-up outcomes were 30-day readmission, 1-year periprosthetic joint infection (PJI), and 1-year mortality. Results: After IPTW, the RBC transfusion rate rose with lower platelet count (Normal, 14.0%; Mild, 27.0%; Moderate, 32.5%; p < 0.001), and transfusion volume peaked in the Moderate group. ICU admission was more frequent (Moderate, 6.0%; Normal, 0.7%; Mild, 0.4%; p = 0.002), and length of stay increased with severity (p = 0.008). Readmission, 1-year PJI, and mortality were comparable across groups. In multivariable analysis, moderate thrombocytopenia was independently associated with RBC transfusion (adjusted odds ratio [aOR], 3.26; 95% confidence interval [CI], 1.51–6.59; p < 0.001) and ICU admission (aOR, 5.46; 95% CI, 1.37–17.41; p = 0.008), but not PJI or mortality. Conclusions: Preoperative thrombocytopenia—particularly in the mild-to-moderate range evaluated in this study—increased perioperative burden after TKA, with higher RBC transfusion and ICU utilization, but was not associated with a significant increase in major postoperative adverse events during 1-year follow-up. Even if not causally responsible, a low preoperative platelet count is a routinely available marker that may flag patients requiring closer perioperative attention. As the associated burden appears largely limited to the hospitalization period, such attentive in-hospital management may allow these patients to achieve favorable outcomes.