Association of interstage timing and prior surgical response with outcomes following staged bilateral total knee arthroplasty: A retrospective cohort study

Abstract Purpose Staged bilateral total knee arthroplasty (BTKA) is increasingly performed, yet the influence of inter‐stage timing on complications and patient‐reported outcomes (PROs) remains unclear. This study evaluated whether timing between staged BTKA procedures was independently associated with 90‐day complications or failure to achieve the minimal clinically important difference (MCID) in 1‐year PROs after the second surgery. Methods Retrospective study of 2410 patients who underwent staged BTKA at a high‐volume single institution (2014–2024). Timing was assessed using quartiles, a ≤6 versus >6‐week cutoff, and as a continuous variable. The primary outcome was any 90‐day complication after the second procedure, as defined by The Knee Society Guidelines. Secondary outcomes included failure to achieve MCID at 1‐year for the knee injury and osteoarthritis outcome score for joint replacement (KOOS‐JR) and veterans RAND 12‐item survey (VRS‐12) physical (PCS) and mental component scores (MCS). Multivariable regression adjusted for demographics, second‐stage preoperative PROs, and complications after the first stage. Results Median time between stages was 245 days. Timing was not independently associated with 90‐day complications or failure to achieve MCID at 1‐year in adjusted models. Prior complications after the first procedure (odds ratio [OR]: 4.01, 95% confidence interval [CI]: 2.21–7.26; p < 0.001) and ASA III–IV (OR: 1.60, 95% CI: 1.05–2.43; p = 0.028) were associated with increased complication risk. Failure to achieve MCID after the first surgery was strongly associated with subsequent MCID failure following the second surgery (KOOS‐JR: OR: 26.34; VRS‐12 PCS: OR: 31.67; MCS: OR: 8.69; all p < 0.001). Conclusions Inter‐stage timing was not independently associated with complications or failure to achieve MCID at 1‐year after adjustment for patient‐level factors. Prior surgical response and ASA classification demonstrated stronger associations with postoperative outcomes following the second stage than timing alone. These findings support individualised surgical planning and shared decision‐making rather than reliance on fixed interval thresholds. Level of Evidence Level III.