Femoral component sagittal alignment and its influence on short-term outcomes in total knee arthroplasty: a systematic review

PURPOSE: Variations in femoral component sagittal alignment may influence clinical outcomes and survival rates following primary total knee arthroplasty (TKA). This study aims to systematically review the influence of femoral component sagittal alignment on short-term outcomes (≥ 6-month follow-up) and potentially characterize an optimal orientation. METHODS: A systematic review was carried out following the PRISMA guidelines to identify studies in PubMed, Cochrane Library, and SPORTDiscus with Full Text databases between January 2010 and April 2025. Eligible studies included adults undergoing primary TKA, quantified sagittal femoral component alignment, and reported at least one of the following outcomes with ≥ 6 months follow-up: patient-reported outcome measures (PROMs), range of motion (ROM), anterior knee pain, or revision/survivorship. Studies not stratifying outcomes by sagittal angle were excluded. After screening 2137 initial results, 10 studies met inclusion and exclusion criteria, with 9 being prospective/retrospective cohort studies and 1 Randomized Control Trial (RCT). Data extraction included study design, demographics, implant type, imaging/measurement method, sagittal alignment definitions, PROMs, ROM, and revision rates. Due to heterogeneity in alignment grouping and outcome reporting, a narrative synthesis was performed rather than a meta-analysis. RESULTS: Ten studies comprising 5,205 TKAs were included, with two robotic-assisted TKA cohorts and eight manual TKA cohorts. Mild flexion of the femoral component was frequently associated with improved short-term outcomes, but results differed by measurement method and outcome definition. Five of eight studies evaluating functional scores and five of six studies evaluating ROM reported improved outcomes with mild flexion compared with neutral or extended alignment. Only two studies explored failure rate, while anterior knee pain was only reported by one study. CONCLUSIONS: Across studies evaluating sagittal alignment in primary TKA, mild flexion of the femoral component was more commonly associated with improved functional outcomes, ROM, implant survival, and pain compared with neutral or extended alignment. However, these associations were inconsistent, and certainty of evidence was generally low or very low for most outcomes, indicating additional RCTs with standardized femoral flexion angle groupings and outcome measurements are needed to further investigate optimal sagittal component positioning.