Fig. 2
From: Does lower educational attainment increase the risk of osteoarthritis surgery? a Swedish twin study
The hazard ratios (HR) per 3 years of education with 95% confidence intervals (CI) for knee and hip OA surgery for male twins born 1951–1980, for matched dizygotic (DZ) and monozygotic (MZ) twins. *Adjusted for body mass index (BMI) at military conscription.**Adjusted for BMI and physical fitness at military conscription. *** Adjusted for BMI, physical fitness at military conscription, birth cohort and place of residence at age 18