Patient Profiles, Implant Survivorships, and Functional Outcomes of Total Knee Arthroplasty in Patients Aged Less than 50 Years in the Past Two Decades: A Systematic Review and Meta-Analysis

Abstract

Background: Evidence supporting the favorable outcomes of total knee arthroplasty (TKA) in patients over 65 years of age is well established; however, less is known in younger cohorts, particularly in those less than 50 years old. Registries have shown an increasing demand for TKA in the younger population. This review aimed to determine the patient profile, implant survival rates, and functional outcomes of TKA in patients aged < 50 years.

Methods: A literature search in PubMed, EMBASE, and Cochrane was conducted, involving studies on TKA in patients aged < 50 years published from January 1, 2004, and December 31, 2024. Data from 15 studies included 17,705 patients. Data synthesis included study design, country, patient demographics, body mass index, follow-up duration, methodological quality (Methodological Index for Non-Randomized Studies score), surgical indications, and implant types. Meta-analyses assessed implant survivorship and postoperative Knee Society functional score and pre- and postoperative range of motion. Statistical analyses were performed using Review Manager version 5.3.

Results: Primary osteoarthritis was the most common indication for TKA in 11 studies, and aseptic loosening was the leading cause of revision in seven studies. Survivorship rates were 97% for less than five years, 95% for five to 10 years, and 87% for greater than 10 years, with the longest mean follow-up at 17 years. The mean postoperative range of motion was 121.5° (95% confidence interval: 107.6 to 135.4), and the mean postoperative Knee Society functional score was 85.3 (95% confidence interval: 79.1 to 91.5).

Conclusions: The patients profiled in this study have a mean age of 41 years, are more likely to be women, and have high body mass index, with comorbidities such as inflammatory joint conditions and predisposing factors, including corticosteroid use and prior surgeries, which may impact outcomes. There was favorable survivorship and functional outcomes comparable with TKA in other age groups of similar follow-ups. These findings aid in patient counseling, expectation setting, and TKA selection for this age group.

Keywords: functional outcome; implant survivorship; meta-analysis; systematic review; total knee arthroplasty; young.