Postoperative Antibiotic Schedule for Knee Replacement
A single preoperative dose of antibiotic is sufficient for knee replacement surgery, with postoperative antibiotics limited to a maximum of 24 hours after surgery. 1
Preoperative Dosing
- Cefazolin 1-2 grams IV should be administered 30-60 minutes before surgical incision to ensure adequate serum and tissue concentrations at the time of incision 1, 2
- For patients weighing ≥120 kg, higher doses of antibiotics are required 1
- For penicillin-allergic patients, clindamycin 900 mg IV as a slow infusion within 60 minutes before incision is the alternative 3
Intraoperative Redosing
- Additional doses should be given intraoperatively only if the procedure exceeds 2-4 hours (typically when duration exceeds two half-lives of the antibiotic) or if significant blood loss occurs (>1.5 L) 1
- For cefazolin, redose with 500 mg to 1 gram during surgery if the procedure is lengthy 2
- For clindamycin, if the procedure exceeds 4 hours, give an additional 600 mg IV dose 3
Postoperative Duration
There is no evidence that prolonging antibiotic prophylaxis after surgery reduces the risk of surgical site infections. 1
- Postoperative antibiotics should be discontinued within 24 hours after surgery 1, 2
- The FDA label for cefazolin allows for 500 mg to 1 gram IV every 6-8 hours for up to 24 hours postoperatively in standard cases 2
- For prosthetic arthroplasty (knee replacement), prophylaxis may be extended to 3-5 days following surgery only in cases where infection would be particularly devastating, though this is not standard practice 2
Key Clinical Considerations
- Single-dose prophylaxis is adequate for the majority of knee replacement procedures 1
- The timing of the preoperative dose is critical—it must be given 30-60 minutes before incision, not earlier, to ensure adequate tissue levels during the period of potential contamination 1
- Extending prophylaxis beyond 24 hours does not provide additional benefit and increases the risk of antibiotic resistance 1
- One retrospective study of 6,489 knee replacements found no change in infection rates when perioperative prophylaxis was decreased from 48 to 24 hours 4
Common Pitfalls to Avoid
- Do not routinely extend antibiotics beyond 24 hours postoperatively—this practice is not evidence-based and promotes resistance 1
- Ensure the preoperative dose is not given too early (>120 minutes before incision) as tissue levels may be inadequate at the time of incision 1
- Do not forget to redose during prolonged procedures, as inadequate intraoperative levels increase infection risk 1