Sore Joint Rub with powerful Arnica and Black Pepper CO2 Extracts. The Arnica flower is well known for its remarkable muscle and joint soothing qualities and for aiding muscles and joints in recovery from injury. CO2 Black Pepper Oil is a circulatory stimulant. As such, it can help soothe the discomfort associated with poor circulation, general stiffness, sprains, and sciatica. The black pepper fragrance is said to support mental clarity and focus. And, as with all of our Sore Muscle Rub blends, SMR-J has a natural fragrance that is sublime.