Characterization of the knee joint phenotype in the Portuguese population

Abstract

Background: Neutral constitutional alignment and neutral joint line obliquity has been the standard alignment strategy for total knee arthroplasty. This one-for-all measure may negatively impact gait pattern and knee biomechanics. Novel alignment strategies surged, considering the variability in phenotypes found across the literature, as different populations may present different phenotype distributions. The Portuguese population has a distinct genetic origin, with no phenotype distribution data. Our objective was to characterise the population’s knee morphology, searching and analysing adjacent joint osteoarthrosis, and calculating the pre-disease coronal alignment. Methods: A retrospective cohort study was conducted. Full-length X-rays performed between 2016-2023 were analysed. Five alignment parameters were measured (LDFA, MPTA, JLCA, TJLA, HKA), and two parameters were calculated (aHKA, JLO). Knees were classified according to the CPAK classification. Results: For the arthritic cohort, CPAK-I (23%) II (20%) were most common, aHKA increases as KL increases (r=0.8352; p<0.001). For the healthy, Type-II (42%) and Type-I (15%) were most common. For paediatric, Type-II (43%) and Type-V (21%) were most common. CPAK Types-VII/VIII/IX were rare. Differences between genders for healthy and arthritic cohorts were statistically significant. The arthritic had higher prevalence of adjacent joint osteoarthritis. Conclusions: The Portuguese population presents a similar knee phenotype comparing with other populations, some differences have been found regarding the Asian continent. The most common phenotype was a neutral alignment if either healthy or paediatric, or a varus alignment if knee OA. Coronal alignment may not have a major impact in the prevalence of ankle and hip osteoarthritis; however, higher prevalence is observed in patients with knee OA.