Despite evidence that topical non-steroidal anti-inflammatory drugs (NSAIDs) and capsaicin are effective in osteoarthritis (OA), it is still unclear why they work for some people but not others. The investigators are undertaking an individual patient data (IPD) meta-analysis to identify responders according to patient characteristics, however, no studies report the presence of synovial hypertrophy or neuropathic-like pain. These two traits are of interest as they may be used to optimise the treatment effects of the two drugs which work via different mechanisms to reduce pain in OA. The investigators are therefore conducting this pilot n-of-1 trial series. This pilot n-of-1 trial series will investigate whether a person with OA, who has a different balance between inflammatory and neuropathic pain, shows a preference between these mechanistically different treatments. The trial will also be used to offer recommendations on the use of n-of-1 trial series for individualised (precision) medicine in OA.