Restoring the coronal plane alignment of the knee (CPAK) phenotype does not consistently improve patient-reported outcomes after primary total knee arthroplasty: A systematic review

To evaluate restoring knee preoperative coronal plane alignment of the knee (CPAK) phenotype, or joint line obliquity (JLO) and arithmetic hip-knee-ankle angle (aHKA), is associated with superior patient-reported outcome measures (PROMs) after primary total knee arthroplasty (TKA). A systematic review was conducted in accordance with the PRISMA guidelines. PubMed, Scopus, Web of Science and Embase were searched from January 2020 to February 2026. Eligible studies included adults undergoing primary TKA who reported validated PROMs, categorized restoration of CPAK phenotype, JLO or aHKA. Two reviewers independently screened, extracted and checked data. Due to heterogeneity in alignment strategies, definitions of restoration and outcome reporting, results were synthesized narratively. Thirteen studies met the inclusion criteria, comprising 1 randomized controlled trial, 1 prospective registry-based study and 11 retrospective cohorts. Follow-up durations ranged from 1 to 5 years. Across studies, restoring the preoperative CPAK phenotype or its coronal components was not consistently linked with higher PROMs. Most studies found comparable PROMs regardless of CPAK phenotypes, JLO and aHKA restoration. Studies showing superior PROMs in restoration subgroups were limited, with small effect sizes and substantial heterogeneity. Evidence was limited by the retrospective design and the small sample size, particularly for valgus and uncommon phenotypes. The current evidence does not demonstrate a consistent association between the CPAK phenotype, JLO, aHKA restoration and improved PROMs after primary TKA. Level III.