Age- and sex-based recovery curves to track functional outcomes in older adults with total knee arthroplasty

Abstract

Background: older adults with total knee arthroplasty (TKA) frequently undergo rehabilitation to address limited knee flexion range-of-motion, quadriceps weakness and gait speed limitations. This study aimed to develop age- and sex-specific recovery curves of knee flexion range-of-motion, quadriceps strength and fast gait speed post-TKA.

Methods: a population-based sample of 2,987 patients undergoing primary TKA participated, of whom 2015 (68%) were 65 years of age or older. At 4, 8 and 12 weeks post surgery, knee flexion range-of-motion, quadriceps strength and fast gait speed were quantified. Quantile regression was used to determine the percentiles of the knee and gait measures.

Results: the various knee and gait measures improved nonlinearly over time, with substantial improvements observed in the 1st 8-10 weeks post surgery. Age-specific, sex-specific recovery curves were developed to show the recovery patterns at multiple percentile levels. A web interface was created to facilitate easy computation of the percentile rank for a given outcome value.

Conclusions: we have provided reference percentile values for knee flexion range-of-motion, quadriceps strength and gait speed recovery post-TKA. Such information may assist rehabilitation professionals in interpreting outcomes and quantifying deviations from the expected recovery pattern.

Keywords: older people; outcome measures; quantile regression; recovery curves; replacement; total knee arthroplasty, knee.