Objectives Chronic widespread pain (CWP) is a common disorder affecting ~10% of the general population and has an estimated heritability of 48-52%. In the first large-scale genome-wide association study (GWAS) meta-analysis, we aimed to identify common genetic variants associated with CWP. Methods We conducted a GWAS meta-analysis in 1,308 female CWP cases and 5,791 controls of European descent, and replicated the effects of the genetic variants with suggestive evidence for association in 1,480 CWP cases and 7,989 controls (P<1×10−5). Subsequently, we studied gene expression levels of the nearest genes in two chronic inflammatory pain mouse models, and examined 92 genetic variants previously described associated with pain. Results The minor C-allele of rs13361160 on chromosome 5p15.2, located upstream of CCT5 and downstream of FAM173B, was found to be associated with a 30% higher risk of CWP (MAF=43%; OR=1.30, 95%CI=1.19-1.42, P=1.2×10−8). Combined with the replication, we observed a slightly attenuated OR of 1.17 (95%CI=1.10-1.24, P=4.7×10−7) with moderate heterogeneity (I2=28.4%). However, in a sensitivity analysis that only allowed studies with joint-specific pain, the combined association was genome-wide significant (OR=1.23, 95%CI=1.14-1.32, P=3.4×10−8, I2=0%). Expression levels of Cct5 and Fam173b in mice with inflammatory pain were higher in the lumbar spinal cord, not in the lumbar dorsal root ganglions, compared to mice without pain. None of the 92 genetic variants previously described were significantly associated with pain (P>7.7×10−4). Conclusions We identified a common genetic variant on chromosome 5p15.2 associated with joint-specific CWP in humans. This work suggests that CCT5 and FAM173B are promising targets in the regulation of pain.

Objective. To establish the natural history of radiographic knee osteoarthritis (OA) over 14 years in a community-based cohort.Methods. We examined women from the Chingford Women's Study, a community-based cohort followed up for more than 14 years. We selected women for whom bilateral radiographs of the knees (with the legs in full extension) were obtained at approximately 5-year intervals. Radiographs were scored for OA in a blinded manner, using Kellgren/Lawrence (K/L) grades. Descriptive statistics and odds ratios (ORs) were used to compare the incidence, worsening, and progression of radiographic knee OA.Results. A complete radiography series was available for 561 of the original 1,003 subjects enrolled in the study. The median age of these subjects at baseline was 53 years (interquartile range 48-58 years). At baseline, 13.7% of the subjects had radiographic knee OA (K/L grade >2) in at least one knee, and the prevalence increased to 47.8% by year 15. The annual cumulative incidence of radiographic knee OA was 2.3% between baseline and year 15. The annual rates of disease progression and worsening between baseline and year 15 were 2.8% and 3.0%, respectively. Subjects with a K/L grade of 1 at baseline were more likely to experience worsening by year 15 compared with subjects with a baseline grade of 0 (OR 4.5, 95% confidence interval 2.7-7.4).Conclusion. This is the longest natural history study of radiographic knee OA to date. The results showed relatively low rates for the incidence and progression of radiographic knee OA; more than half of all subjects had no radiographic evidence of knee OA over a 15-year period of time. Subjects with a baseline K/L grade of 1 were more likely than subjects with other baseline K/L grades to experience worsening of knee OA.

ObjectiveTo assess if a coding variant in the gene encoding transient receptor potential cation channel, subfamily V, member 1 (TRPV1) is associated with genetic risk of painful knee osteoarthritis (OA).MethodsThe Ile585Val TRPV1 variant encoded by rs8065080 was genotyped in 3270 cases of symptomatic knee OA, 1098 cases of asymptomatic knee OA and 3852 controls from seven cohorts from the UK, the USA and Australia. The genetic association between the low-pain genotype Ile–Ile and risk of symptomatic and asymptomatic knee OA was assessed.ResultsThe TRPV1 585 Ile–Ile genotype, reported to be associated with lower thermal pain sensitivity, was associated with a lower risk of symptomatic knee OA in a comparison of symptomatic cases with healthy controls, with an odds ratio (OR) of 0.75 (95% CI 0.64 to 0.88; p=0.00039 by meta-analysis) after adjustment for age, sex and body mass index. No difference was seen between asymptomatic OA cases and controls (OR=1.02, 95% CI 0.82 to 1.27 p=0.86) but the Ile–Ile genotype was associated with lower risk of symptomatic versus asymptomatic knee OA adjusting for covariates and radiographic severity (OR=0.73, 95% CI 0.57 to 0.94 p=0.0136). TRPV1 expression in articular cartilage was increased by inflammatory cytokines (tumour necrosis factor α and interleukin 1). However, there were no differences in TRPV1 expression in healthy and arthritic synovial tissue.ConclusionsA genotype involved in lower peripheral pain sensitivity is significantly associated with a decreased risk of painful knee OA. This indicates a role for the pro-nociceptive gene TRPV1 in genetic susceptibility to symptomatic knee OA, which may also be influenced by a role for this molecule in cartilage function.