IMPORTANCE As individuals age, they often face a variety of health challenges. Physical resilience indicates how well a person can cope with and recover from physical challenges, which is crucial for maintaining independence and quality of life in older age.

OBJECTIVE To develop a multivariate phenotype of physical resilience based on individual recovery dynamics before and after a clinical stressor.

DESIGN, SETTING, AND PARTICIPANTS This observational study included 112 individuals aged 60 and older who underwent elective total knee replacement for degenerative joint disease between December 2, 2019, and January 4, 2023. Physical function was assessed before surgery and at 1, 6, and 12 months post-surgery to characterize resilience trajectories.

EXPOSURE Elective total knee replacement surgery for degenerative joint disease.

MAIN OUTCOMES AND MEASURES A multivariate resilience phenotype was derived from physical function trajectories assessed using the Short Physical Performance Battery, the Pittsburgh Fatigability Scale-Physical Subscale, the KOOS Quality of Life, and the SF36-Physical Component Score. This phenotype was validated against surrogate markers (i.e., frailty, self-reported health) and determinants (e.g., the Charlson Comorbidity Index) of recovery potential (aka resilience capacity).

RESULTS The study identified distinct resilience profiles across four measures: 4 profiles for the Short Physical Performance Battery and the KOOS Quality of Life, 3 each for the Pittsburgh Fatigability Scale-Physical Subscale and the SF36-Physical Component Score, showing varied baseline levels and/or change rates over 12 months. By combining and analyzing resilience profiles across measures, two distinct groups emerged: 35.7% classified as non-resilient and 64.3% as resilient. The non-resilient group had a higher prevalence of frailty (35.0% vs. 9.7%, p<0.01), poor or fair self-reported health (45.0% vs. 5.6%, p<0.01), and a moderate/severe comorbidity burden (Charlson Comorbidity Index >2; 27.5% vs. 11.1%, p=0.06).

CONCLUSIONS AND RELEVANCE The distinct recovery trajectories observed after the surgery indicated varying resilience levels that were not fully explained by baseline status. This research underscores the importance of resilience in surgical recovery and could pave the way for better patient care by focusing on individual resilience capacities and shifting the focus from managing health conditions to promoting recovery and overall well-being.

Question Can recovery trajectories of physical function following total knee replacement surgery serve as indicators of resilience to physical stressors?

Findings An observational study of adults aged 60+ undergoing elective total knee replacement surgery found distinct 12-month recovery paths, with 35.7% classified as non-resilient and 64.3% as resilient, independent of pre-surgery health or fitness.

Meaning This finding suggests that resilience is measurable and may require dynamic testing, rather than just relying on baseline health, to assess recovery potential.

The authors have declared no competing interest.

This study was supported by research grant under UH3AG056933 from the National Institute on Aging, National Institutes of Health, United States of America.

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

This study is approved by the Johns Hopkins University School of Medicine Institutional Review Board (IRB00167996)

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

Data Data available: Yes Data types: Deidentified participant data, data dictionary How to access data: The datasets generated and/or analyzed during this study are not publicly available to protect participant confidentiality. However, they can be obtained from the corresponding author upon reasonable request. When available: With publication Supporting Documents Document types: None Additional Information Who can access the data: Researchers whose proposed use of the data has been approved. Types of analyses: Secondary analyses. Mechanisms of data availability: Data will be made available without investigator support upon approval of a proposal and execution of a signed data access agreement.