# Preserved Efficacy of Intra-articular Autologous Protein Solution in Patients Aged Over 80 Years With Knee Osteoarthritis: A Comparison With Younger Counterparts

## TL;DR

This study shows that knee injections of autologous protein solution work well in patients over 80 for osteoarthritis, similar to younger patients.

## Contribution

The study provides evidence that APS injections are effective in elderly patients over 80, a group underrepresented in prior research.

## Key findings

- APS injections improved patient-reported outcomes in both elderly and younger patients.
- Elderly patients showed higher initial improvements in daily living and quality of life, but effects lasted shorter.
- KSS scores improved over time in both groups, except for the expectation subscale.

## Abstract

Introduction: With ongoing societal aging, the demand for regenerative medicine has increased. Recently, reports demonstrating the efficacy of knee regenerative therapies have increased, although substantial proportions of these studies involved relatively younger populations. However, in Japan, where our hospital is located, it is common for patients well beyond the WHO-defined elderly age of 65 years to present with a desire for regenerative therapy. This retrospective cohort study investigated the utility of autologous protein solution (APS) knee joint injections by comparing their effects in patients aged 80 years and older and those younger than 80 years.

Methods: From July 2021 to August 2023, we administered single APS injections into the knee joints of patients diagnosed with osteoarthritis. Clinical assessment was conducted at baseline and at one and six months post-injection. Forty-one patients (44 knees) who completed all scheduled assessments were included in this analysis. Subjects were stratified into group E (≥80 years old) or group Y (<80 years old). Clinical evaluations included assessments of joint range of motion, inflammatory biomarkers (C-reactive protein), radiographic Kellgren-Lawrence classification, MRI findings including bone marrow edema, and standardized patient-reported outcome measures (Knee Injury and Osteoarthritis Outcome Score {KOOS} and Knee Society Score {KSS}), with KSS subdomain scores normalized to a 100-point scale.

Results: No distinct intergroup differences were observed for knee range of motion, blood test parameters, or MRI findings. Group E had the highest scores on the KOOS activities of daily living and quality of life subscales at one month post-APS administration; both subscale scores decreased at six months post-administration, whereas these subscale scores consistently increased over time in group Y. Compared with the findings in prior research reporting the minimum clinically important difference after platelet-rich plasma administration, the findings at six months after APS administration were superior for all KOOS subscales, excluding sports, in both groups. Concerning KSS scores, most subscale scores consistently increased throughout the follow-up period in both groups, whereas the expectation subscale score tended to decrease over time, likely reflecting the evolution of expectations after surgery.

Conclusions: Intra-articular APS injections demonstrated clinical efficacy in patients aged 80 years and older. When the analysis was limited to those who continued follow‑up at both one and six months after treatment, a tendency toward a shorter duration of effect was still observed, indicating the need for careful patient selection.