More clinical research is needed to determine if there are efficacious (effective and low-cost) evidence-based exercise programs for pain reduction and functional improvement in patients with thumb CMC osteoarthritis. The investigators are interested in the effect of FDI strengthening in patients with thumb CMC osteoarthritis. Therefore, the investigators hypothesized that there is no difference in the change of lateral pinch strength at 12 weeks between patients treated with a splint versus patients treated with a splint and FDI strengthening for thumb CMC osteoarthritis. We also tested the same hypothesis for 3-point chuck strength, VAS for pain, and PROMIS Upper Extremity CAT.