To investigate the narrow sense heritability for the four osteoarthritis disease definitions, we ran LDscore42 (link), which uses summary statistics at common-frequency variants genome-wide (independent of P value thresholds) and LD estimates between variants while accounting for sample overlap. To calculate the population prevalence in the UK (65 million people), we consulted Arthritis Research UK figures: 8.75 million people have symptomatic osteoarthritis, while 2.46 and 4.11 million people have osteoarthritis of the hip and the knee, respectively. We assumed that 2.46+4.11 million people have osteoarthritis of the hip and/or the knee. We estimated the phenotypic variance explained by the 99previously and newly reported variants that reached genome-wide significance in the meta-analysis between UK Biobank and arcOGEN, as a function of allele frequency (Figure 2; Supplementary Table 17). The phenotypic variance explained by a variant is) ln(OR)2 × 2 × EAF × (1 − EAF), where ln(OR) is the natural logarithm of the OR of the variant in the meta-analysis and EAF is its weighted effect allele frequency across UK Biobank and arcOGEN. Variants associated with hip osteoarthritis tend to have larger effect size estimates and hence explain more of the phenotypic variability (Figure 2; Supplementary Table 17). The hip osteoarthritis dataset is the smallest in both the UK Biobank and arcOGEN cohorts (18% and 59% fewer cases compared to knee osteoarthritis and osteoarthritis at any joint in UK Biobank, respectively).