Individual Patient-reported Activity Levels before and after Joint Arthroplasty Are Neither Accurate nor Reproducible

Natalie H. Vaughn, Mitchell F. Dunklebarger, Mark W. Mason

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


BackgroundPatients often are asked to report walking distances before joint arthroplasty and when discussing their results after surgery, but little evidence demonstrates whether patient responses accurately represent their activity.Questions/purposesAre patients accurate in reporting distance walked, when compared with distance measured by an accelerometer, within a 50% margin of error?MethodsPatients undergoing THA or TKA were recruited over a 16-month period. One hundred twenty-one patients were screened and 66 patients (55%) were enrolled. There were no differences in mean age (p = 0.68), proportion of hips versus knees (p = 0.95), or sex (p = 0.16) between screened and enrolled patients. Each patient wore a FitBitTM Zip accelerometer for 1 week and was blinded to its measurements. The patients reported their perceived walking distance in miles daily. Data were collected preoperatively and 6 to 8 weeks postoperatively. Responses were normalized against the accelerometer distances and Wilcoxon one-tailed signed-rank testing was performed to compare the mean patient error with a 50% margin of error, our primary endpoint.ResultsWe found that patients' self-reported walking distances were not accurate. The mean error of reporting was > 50% both preoperatively (p = 0.002) and postoperatively (p < 0.001). The mean magnitude of error was 69% (SD 58%) preoperatively and 93% (SD 86%) postoperatively and increased with time (p = 0.001).ConclusionsPatients' estimates of daily walking distances differed substantially from those patients' walking distances as recorded by an accelerometer, the accuracy of which has been validated in treadmill tests. Providers should exercise caution when interpreting patient-reported activity levels.Level of EvidenceLevel III, diagnostic study.

Original languageEnglish (US)
Pages (from-to)536-544
Number of pages9
JournalClinical orthopaedics and related research
Issue number3
StatePublished - Mar 1 2019

All Science Journal Classification (ASJC) codes

  • Surgery
  • Orthopedics and Sports Medicine


Dive into the research topics of 'Individual Patient-reported Activity Levels before and after Joint Arthroplasty Are Neither Accurate nor Reproducible'. Together they form a unique fingerprint.

Cite this