Understanding the biomechanical “spread” of joint pain: knee pain predicts subsequent shoulder pain and this is mediated by leg weakness. Data from the osteoarthritis initiative

Joint pain is common in older adults; typically multiple joints are involved. A greater number of painful sites is associated with higher levels of pain intensity in affected joints, more functional impairment and poorer quality of life. However, little is known about the pattern of multi-site joint pain development. We aimed to assess whether the number of painful joints increases over time, whether pain in certain joints precedes pain in others, and to assess whether the association is mediated by weakness in a cohort of older adults with painful knee osteoarthritis or at risk of knee osteoarthritis in the NIH Osteoarthritis Initiative (OAI).