BACKGROUND Implant infection is serious; prevention is mandatory, and requires assessment.The present study assessed the incidence of deep surgical-site infection (SSI) at 1 year following total knee arthroplasty (TKA) and adherence to skin preparation, antibiotic prophylaxis,screening and prevention in case of methicillin-resistant S. aureus (MRSA). OBJECTIVE Adherence to prevention measures reduces infection risk secondary to TKA. METHODS A prospective study of the incidence of SSI following primary TKA was run from December 1st 2005 to December 31st 2006 in a continuous series of 364 operations in 359 patients, excluding cases of septic or aseptic revision. Each implant was followed up for 12 months. Adherence to practice was assessed by independent observers. Antibiotic prophylaxis was assessed; skin preparation was scored (out of 10); MRSA was systematically screened for, and preventive measures were assessed in positive cases. Median follow-up was 12 months.Patients with less than 11 months' FU were contacted by telephone. Median age was 72 years(range, 45-92 years). Eighty-seven percent of patients had ASA scores of 2; 14% were diabetic,and 42% obese. Mean surgery time was 70 min (range, 30-164 min). Among the implants, 81.5% were cemented. Eighty-six percent of operations had NNIS scores of 0. Infection risk linked to theater environment and teams was under control. RESULTS Fourteen patients were lost to follow-up and excluded from analysis. The incidence of infection was 1.4% (n = 5/350) (95% CI [0.41-3.22]). Three of the infections were early (</-1 month), and two were polymicrobial. Antibiotic prophylaxis was implemented correctly in 99% of cases, with skin preparation scores of 8.75 in 61% of cases and of 10 in 39%. Among the patients, 2.5% were MRSA-positive, none of whom developed infection. Infection prevention measures were applied in only half of the MRSA-positive cases. No MRSA-positive patients developed SSI. CONCLUSIONS SSI incidence in the present series was low, but certainly underestimated. Assessment found good implementation of infection prevention protocols, with SSI occurring randomly with regard to adherence parameters (antibiotic prophylaxis, skin preparation, MRSA status). CONCLUSIONS Our hypothesis could not be confirmed. The study was mandatory for a health-care institution, and indispensable from a legal standpoint. METHODS Level IV. Prospective prognostic study.