Restricted kinematic alignment in total knee arthroplasty achieves equivalent or superior functional outcomes to mechanical alignment without compromising implant survivorship: A systematic review.

Abstract

This systematic review assesses the viability of restricted kinematic alignment compared to mechanical alignment by assessing clinical outcomes, radiological findings, and patient-reported outcome measures. Median follow-up was 20.3 months. Both RCTs and observational studies are included in this review. A search was carried out according to PRISMA guidelines over PubMed, Embase, Cochrane and Web of Science databases. The following search string, ('restricted kinematic alignment' AND 'mechanical alignment') AND ('total knee arthroplasty' OR 'total knee replacement') was used. Titles, abstracts and keywords were screened against predetermined inclusion and exclusion criteria. Data was extracted by two independent reviewers and conflict was resolved by consensus. A total of 110 papers between 1975 and January 2025 were screened with 11 texts included in the final analysis.Restricted kinematic alignment achieved superior FJS (p = 0.044) and KSS (p = 0.028) at 12 and 24 months respectively compared to mechanical alignment. Radiographic analyses confirmed coronal limb alignment and femoral/tibial component positioning remained within defined safe zones, with no significant increase in outliers. Importantly, complication and revision rates did not differ significantly between groups, indicating no compromise in short-term safety which is defined as follow-up less than five years. This analysis suggests restricted kinematic alignment provides functional advantages whilst adhering to strict 'intraoperative safe zones' with no increase in short-term complications. However, surgical technique remains variable with some studies using robotic assisted surgery and others utilising calipered kinematic adjustments or navigation-assisted resections. Long-term implant durability also remains a crucial unanswered question. Level III.