Original research| Volume 100, ISSUE 11, P2106-2112, November 2019

Predicting Mobility Limitations in Patients With Total Knee Arthroplasty in the Inpatient Setting



      To develop a prediction model for postoperative day 3 mobility limitations in patients undergoing total knee arthroplasty (TKA).


      Prospective cohort study.


      Inpatients in a tertiary care hospital.


      A sample of patients (N=2300) who underwent primary TKA in 2016-2017.


      Not applicable.

      Main Outcome Measure

      Candidate predictors included demographic variables and preoperative clinical and psychosocial measures. The outcome of interest was mobility limitations on post-TKA day 3, and this was determined a priori by an ordinal mobility outcome hierarchy based on the type of the gait aids prescribed and the level of physiotherapist assistance provided. To develop the model, we fitted a multivariable proportional odds regression model with bootstrap internal validation. We used a model approximation approach to create a simplified model that approximated predictions from the full model with 95% accuracy.


      On post-TKA day 3, 11% of patients required both walkers and therapist assistance to ambulate safely. Our prediction model had a concordance index of 0.72 (95% confidence interval, 0.68-0.75) when evaluating these patients. In the simplified model, predictors of greater mobility limitations included older age, greater walking aid support required preoperatively, less preoperative knee flexion range of movement, low-volume surgeon, contralateral knee pain, higher body mass index, non-Chinese race, and greater self-reported walking limitations preoperatively.


      We have developed a prediction model to identify patients who are at risk for mobility limitations in the inpatient setting. When used preoperatively as part of a shared-decision making process, it can potentially influence rehabilitation strategies and facilitate discharge planning.


      List of abbreviations:

      c-index (concordance index), CI (confidence interval), TKA (total knee arthroplasty)
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