Aims. The aim of this study was to describe the pattern of revision indications for unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) and any change to this pattern for UKA patients over the last 20 years, and to investigate potential associations to changes in surgical practice over time. Methods. All primary knee arthroplasty surgeries performed due to primary osteoarthritis and their revisions reported to the Danish Knee Arthroplasty Register from 1997 to 2017 were included. Complex surgeries were excluded. The data was linked to the National Patient Register and the Civil Registration System for comorbidity, mortality, and emigration status. TKAs were propensity score matched 4:1 to UKAs. Revision risks were compared using competing risk Cox proportional hazard regression with a shared γ frailty component. Results. Aseptic loosening (loosening) was the most common revision indication for both UKA (26.7%) and TKA (29.5%). Pain and disease progression accounted for 54.6% of the remaining UKA revisions. Infections and instability accounted for 56.1% of the remaining TKA revision. The incidence of revision due to loosening or pain decreased over the last decade, being the second and third least common indications in 2017. There was a decrease associated with fixation method for pain (hazard ratio (HR) 0.40; 95% confidence interval (CI) 0.17 to 0.94) and loosening (HR 0.29; 95% CI 0.10 to 0.81) for cementless compared to cemented, and units UKA usage for pain (HR 0.67, 95% CI 0.50 to 0.91), and loosening (HR 0.51; 95% CI 0.37 to 0.70) for high usage. Conclusion. The overall revision patterns for UKA and TKA for the last 20 years are comparable to previous published patterns. We found large changes to UKA revision patterns in the last decade, and with the current surgical practice, revision due to pain or loosening are significantly less likely. Cite this article: Bone Jt Open 2023;4(12):923–931

Purpose of the Study. To identify trends in patient satisfaction of their knee arthroplasty, total and unicompartmental, one year post primary knee arthroplasty surgery, with reference to age, gender and primary diagnosis, from 1990 to 2008. Methods & Results. The Trent Arthroplasty Register was established in 1990 to collect prospective data on knee arthroplasty surgery Data has been recorded relating to 48,929 knee arthroplasties in the period 1990-2008. Self-administered questionnaires were mailed to patients 1 year after their surgery. This PROMS data has been analysed to identify trends in 25,521 patients. 62% (24,648) of knee arthroplasties were performed for osteoarthritis and 32% (1,233) for rheumatoid arthritis. 83.6% of osteoarthritic patients (20,244) were satisfied with their knee 1 yr post surgery, 8.5% (2055) unsure and 7.9% dissatisfied. Comparable figures for patients with rheumatoid arthritis were 81.3% (1,028) satisfied, 10.3% (130) unsure and 8.4% dissatisfied. Overall, there was no significant difference in satisfaction rates between different diagnostic groups of patients. In osteoarthritic patients, satisfaction rates have remained the same throughout the last 18 years, in different time periods. The satisfaction rate was 83.2% for the period 1990-1994, 80.9% for 1995-1999, 86.5% for 2000-2004 and 84.1% for 2005-2007. There was no statistically significant difference between the levels of satisfaction for these time periods. The age of the patient did not affect the satisfaction rate. Conclusion. There was no significant difference in satisfaction rates between male and female patients. Overall, this study demonstrates that patient satisfaction with knee arthroplasty surgery has remained high and is irrespective of age, gender and primary diagnosis. A significant minority of patients, however, continue to remain dissatisfied with their knee implants and this figure has remained static over an 18-year period