Introduction <p>Post-operative delays in blood oxygen recovery are sometimes observed after total knee arthroplasty (TKA), with obstructive sleep apnoea (OSA) being a contributing factor. This study aimed to examine the prevalence of OSA and its correlation with post-operative oxygen saturation (SpO2) recovery in patients undergoing TKA for knee osteoarthritis (OA).</p> Materials and methods <p>This was an observational case-control study including patients with knee OA who underwent TKA between January 2018 and October 2021. Pre-operative symptoms of OSA were assessed, and the apnoea-hypopnoea index, 3% oxygen desaturation index (ODI), average SpO2 and sleep body positions were measured using sleep testing devices. Knee function was evaluated using the 2011 Knee Society Score and range of motion (ROM).</p> Results <p>A total of 240 patients (41 males and 199 females) with a mean age of 74 years (range 51–93 years) were included in this study. Of the 240 patients, 49 (20.4%) had no OSA, 104 (43.3%) had mild OSA and 87 (36.3%) had moderate to severe OSA. OSA severity increased with a higher body mass index. Diabetes prevalence increased as the severity of OSA increased. OSA severity did not affect pre-operative knee function scores or ROM. However, higher ODI and lower pre-operative SpO2 were associated with increased OSA severity. Additionally, patients with severe OSA exhibited a greater proportion of supine sleep time and delayed post-operative oxygen discontinuation.</p> Conclusions <p>Patients with knee OA scheduled for TKA have a high prevalence of OSA. Increased OSA severity delay oxygen discontinuation after TKA.</p>