Comparable Survivorship and Patient-Reported Outcomes Following Unicompartmental Knee Arthroplasty in Obese and Non-Obese Patients: An Updated Systematic Review.

Abstract

The influence of obesity on outcomes after unicompartmental knee arthroplasty (UKA) remains controversial. This systematic review evaluated whether obesity affects survivorship, reasons for revision, and patient-reported outcome measures (PROMs) following UKA. The MEDLINE, EMBASE, and CENTRAL search engines were searched from inception to October 15, 2025. Eligible studies reported UKA outcomes stratified by body mass index (BMI) or included cohorts exclusively composed of obese patients (BMI ≥ 30). Survivorship at short- (less than 5-year), mid- (five to less than 10-year), and long-term (≥ 10-year) follow-up was compared across non-obese (BMI less than 30), obese (BMI 30 to less than 40), and morbidly obese (BMI ≥ 40) patient cohorts using meta-analysis. The secondary outcomes included reasons for revision and PROMs. There were 27 studies (27,271 knees) that were included (mean age, 65 years; mean BMI, 30.7). Less than 5-year survivorship for non-obese, obese, and morbidly obese groups was 95.5, 95.3, and 95.8%, respectively (P = 0.943). The five- to less than 10-year survivorship was 95.3, 92.1, and 90.6%, respectively (P = 0.034), with adjusted pairwise comparisons only demonstrating a non-significant trend toward lower survivorship in morbidly obese patients compared to non-obese (90.6 versus 95.3%; adjusted P = 0.065). The ≥ 10-year survivorship was 92.1, 92.9, and 88.7%, respectively (P = 0.460). Across 14,319 knees with documented revision etiology, the most common causes were aseptic loosening (47.0%), pain without loosening (16.2%), and progression of osteoarthritis (15.2%). Morbidly obese patients demonstrated proportionally higher rates of progressive osteoarthritis and technique-related failure. The PROMs improved meaningfully across all BMI categories, though postoperative scores tended to be slightly lower in obese and morbidly obese individuals. Obesity should not be considered an absolute contraindication to UKA. Obese patients achieve substantial functional improvement and demonstrate survivorship comparable to non-obese patients across less than 5-year, five to less than 10-year, and ≥ 10-year follow-up. Revision reasons differed across BMI categories, with morbidly obese patients more often requiring secondary surgery for progression of arthritis, a modifiable risk factor that can inform individualized preoperative counseling and risk mitigation strategies.