St. John's wort is an herb that may treat your arthritis, sciatica and back pain. According to the National Center for Complementary and Alternative Medicine, St. John's wort, also known as hypericum perforatum, is a shrubby plant bearing clusters of yellow flowers.rnica is an herb that may be beneficial in treating arthritis, sciatica and back pain. The Memorial Sloan-Kettering Cancer Center states that arnica, also known as arnica montana or mountain tobacco, is derived from the flowers and rhizome, or underground stem, of the plant.