Capsaicin from chilli peppers seems to provide pain relief in arthritis sufferers according to placebo controlled clinical trials.It seems able to influence a neuropeptide called ‘substance P’ which is involved in inflammation and pain in the disease. In a double-blind, placebo controlled, randomised trial involving 70 people over 4 weeks RHEUMATOID ARTHRITIS SUFFERERS REPORTED A 57% RELIEF, and OSTEOARTHRITIS SUFFERERS A 33% RELIEF.
The capsaicin was administered in a cream and almost half of patients experienced some burning effect. Although this caused two patients to withdraw from the trial, the overall conclusion was that the treatment was effective and safe.
Ref: http://www.ncbi.nlm.nih.gov/pubmed/1954640