67 patients with de Quervain tenosynovitis were randomized to receive treatment with a corticosteroid injection (CSI) alone or in combination with thumb spica casting (TSC). The effectiveness of each treatment was examined and compared in terms of success rate, pain intensity, and functional outcomes. Within 3 weeks, both groups experienced significant improvements in success rates compared to their respective baseline outcomes, but with CSI + TSC achieving significantly better results when compared to CSI alone over the 6 month follow-up. The same trend was found in pain intensity and functional outcome at 6 months.