Presurgery osteoarthritis severity over 10 years in 2 Ontario prospective total knee replacement cohorts: a cohort study.

Background: It has been suggested that total knee replacement is being performed in people with less-severe osteoarthritis. We aimed to determine whether there were differences in the presurgery profile, symptoms and disability of 2 cohorts who underwent total knee replacement over a 10-year period.

Methods: Patients aged 18-85 years undergoing primary total knee replacement for osteoarthritis at 1 of 4 sites in Toronto and Strathroy, Ontario, were recruited in a cohort study during 2006-2008 (cohort 1) and 2012-2015 (cohort 2). Patients undergoing unicompartmental or revision arthroplasty were excluded. Demographic and health (body mass index [BMI], comorbidity) variables and osteoarthritis severity, as assessed with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the disability component of the Late-Life Function and Disability Instrument (LLFDI-D), were collected before surgery. We calculated proportions, means and standard deviations with 95% confidence intervals (CIs) for all data. We constructed density plots by tertile score for the WOMAC pain and physical function subscales and the LLFDI-D limitation scale.

Results: There were 494 patients in cohort 1 and 251 patients in cohort 2. There were no differences in age, sex, education, living status, BMI, comorbidity, pain severity or disability between the cohorts based on overlapping 95% CIs and the density plots. More patients in cohort 1 than in cohort 2 were single (176 [35.6%], 95% CI 32.5%-41.1% v. 63 [25.1%], 95% CI 20.3%-31.0%). Patients in cohort 2 reported less limitation in higher-demand activities than did those in cohort 1 (mean score on LLFDI-D 62.3 [95% CI 60.7-63.9] v. 59.2 [95% CI 58.2-60.2]).

Interpretation: The patient profile and reported osteoarthritis severity were similar in 2 cohorts that had total knee replacement over a 10-year period. This suggests that increasing total knee replacement volumes over this period likely were not driven by these factors.