Summary

Older age is associated with slower but significant improvement in knee function and physical health after surgery, accounting for patients’ gender, BMI, lower range of motion, or preoperative joint alignment.

Abstract

Introduction

Total knee arthroplasty (TKA) often improves pain, function, and overall health in knee osteoarthritis (OA) patients. However, recovery varies among patients, and ageing is often thought to impact outcomes. The effects of age on TKA recovery are still not well understood, and there are concerns about the risks and benefits of surgery for as the average TKA patient is around 70 years old. In this study, we investigated how age influences recovery after TKA.

Methods

In this retrospective study, a total of 1723 patients who received a TKA between 2018-mid 2023 and had 1-year post-operative PROMs data were included. Patients completed the Oxford Knee Score (OKS), Forgotten Joint Score (FJS), VR-12 Mental and Physical Scores pre-operation and 1-year post-operation. Medical Care Satisfaction, Knee Normality Score, and VAS (0-100) were recorded 3 months and 1-year post-operation. Data was analysed using linear regression and adjusted for gender, body mass index (BMI), range of motion (ROM), and joint alignment.

Results

Of the 1723 participants, 50.7% were males, and the mean age was 69.4 years with an average BMI of 30.
Pre-operatively, PROMs were positively associated with age [OKS (β=0.11, p<0.001), FJS (β=0.36, p=<0.001), and VR-12 Mental score (β=0.11, p=0.002)]. However, after adjusting for covariates, only pre-operative FJS remained significant (β=0.32, p=0.003).
At 3 months post-operation, Medical Care Satisfaction (β=-0.25, p=0.04) and Knee Normality Score (β=-0.43, p=0.02) were lower in older patients, while VAS increased with age (β= 0.36, p=0.03). After adjusting for covariates, these associations lost their significance.
At the 1-year follow-up, advancing age was associated with a decline in OKS (β=-0.04, p=0.02), VR-12 Physical Score (β=-0.17, p=<0.001), and Medical Care Satisfaction (β=-0.13, p=0.01). While decline in knee function and overall health were expected, their effect sizes were smaller than predicted. After adjusting for covariates, only OKS (β=-0.12, p=<0.001) and VR-12 Physical Score (β=-0.27, p<0.001) remained significant, whilst FJS (β=-0.40, p=0.03) gained statistical significance.
Improvement in delta PROMs scores from before surgery to one year after surgery was notable. On average, the FJS improved by 48.3 points, OKS by 16.3 points, and the VR-12 Physical Score by 14.6 points. These improvements indicate positive outcomes in joint function and overall physical health following the operations However, longitudinal multivariate analysis revealed an inverse relationship between age and PROMS, hence older patients exhibited lower FJS (β=-0.81, p<0.001), OKS (β=-0.19, p<0.001), and VR-12 Physical Score (β=-0.21, p<0.001) scores in comparison to younger patients.

Conclusion

Older age is associated with slower but significant improvement in knee function and physical health after surgery, accounting for patients’ gender, BMI, lower range of motion, or preoperative joint alignment. Furthermore, older patients had equivalent levels of patient satisfaction, knee normality, VAS scores, and mental health as their younger counterparts. These findings highlight the relationship between age and recovery following TKA, emphasising the need for tailored interventions and rehabilitation to improve outcomes for older patients considering TKA.