This study will test the Pain Relief Patch (PRP), a new device containing LEDs that is to be worn on the skin of the painful area, to see if it is effective in relieving chronic musculoskeletal back pain. It will also test the safety of the patch. The LEDs in the PRP emit a certain kind of light (peak wavelength 453 nm) that stimulates the production of nitric oxide (NO) in the skin. NO has been shown to induce a number of actions that should contribute to pain relief, including relaxation of smooth muscle cells, dilation of blood vessels, increased concentrations of oxygen in the cells and washout of metabolic byproducts and toxins caused by cell injury or death. Participants in one treatment group will be treated 5 times over 2 weeks for 30 minutes with PRP patches in the clinic. Participants in the control arm will be treated for the same length of time with a similar device that contains LEDs that emit another wavelength of light that does not induce production of NO. To prevent the influence of expectations on the results, neither the participants nor the medical staff directly responsible for their treatment will be told with which of the test patches the participants are treated. Other clinic staff will be responsible for all activities that could identify treatment arm, including putting the devices on and removing them, and examining the condition of the participants' skin before and after treatment. To get an accurate measure of how effective the devices are, participants will score their pain several times before the treatment period begins, as well as before and after each treatment. They will also complete several pain questionnaires during the study.