Acetone is the one in Absorbine and I'd consider it for arthritis, but want to avoid it for the moment.
Salicylic acid is an anti-inflammatory itself and worth consideration; I'd be interested in what forms it's available in as a cosmetics additive.
Wintergreen grows wild and abundantly in my area and harvesting enough to process for oil would be a cinch. Oh geez, if this means I get to learn to steam-distill essential oils... lol! I love having o-chem glassware at my disposal...