We would like to thank Gao et al for their interest in our paper ‘Painful knee but not hand osteoarthritis is an independent predictor of mortality over 23 years follow-up of a population-based cohort of middle-aged women’.

Gao et al highlighted a number of issues related to a discordance between pain and radiographic changes and sensitivity of the pain assessment. Although a single definition of knee osteoarthritis (KOA) remains elusive, the presence of knee pain is the main symptom of knee osteoarthritis(OA)(2-4) and there is still a strong relationship between pain and ROA. (5, 6) Notwithstanding this, a substantial number of patients with radiographic knee osteoarthritis (ROA) are asymptomatic. Although OA is the most common ‘source’ of knee pain in ROA, it is true, as pointed out by Gao et al. that many other diagnoses may be judged to account for a patient’s symptoms including bursitis, tendinopathies and overuse injuries. In this cohort of middle aged to elderly women, we feel that these alternative causes will not be prevalent. We defined pain as the presence of side-specific knee pain in the preceding month, and painful radiographic KOA as knee specific pain and presence of ROA. We have performed additional analyses to further address the queries of Gao at al.