We present detailed information about early morbidity after aseptic revision knee replacement from a nationwide study. All aseptic revision knee replacements undertaken between 1st October 2009 and 30th September 2011 were analysed using the Danish National Patient Registry with additional information from the Danish Knee Arthroplasty Registry. The 1218 revisions involving 1165 patients were subdivided into total revisions, large partial revisions, partial revisions and revisions of unicondylar replacements (UKR revisions). The mean age was 65.0 years (27 to 94) and the median length of hospital stay was four days (interquartile range: 3 to 5), with a 90 days re-admission rate of 9.9%, re-operation rate of 3.5% and mortality rate of 0.2%. The age ranges of 51 to 55 years (p = 0.018), 76 to 80 years (p < 0.001) and ≥ 81 years (p < 0.001) were related to an increased risk of re-admission. The age ranges of 76 to 80 years (p = 0.018) and the large partial revision subgroup (p = 0.073) were related to an increased risk of re-operation. The ages from 76 to 80 years (p < 0.001), age ≥ 81 years (p < 0.001) and surgical time > 120 min (p < 0.001) were related to increased length of hospital stay, whereas the use of a tourniquet (p = 0.008) and surgery in a low volume centre (p = 0.013) were related to shorter length of stay. In conclusion, we found a similar incidence of early post-operative morbidity after aseptic knee revisions as has been reported after primary procedures. This suggests that a length of hospital stay ≤ four days and discharge home at that time is safe following aseptic knee revision surgery in Denmark.