The purpose of this study was to compare the effects of two 6-week splint and exercise regimens for patients with trapeziometacarpal osteoarthritis. Forty participants were enrolled in a randomised, controlled clinical trial. The experimental group received a newly designed thumb strap splint and an abduction exercise regimen, whereas the control group received current clinical practice consisting of a short opponens splint and a pinch exercise regimen. Outcome measures included pain (VAS at rest in cm), strength (tip pinch in kg), and hand function (Sollerman Test of Hand Function scored out of 80), measured by a blinded assessor at Weeks 0, 2, and 6. By Week 6 there was no significant difference in the extent of mean improvement between the groups in: pain, 0.5 cm (95% CI -1.1 to 2.1); strength, 0.1 kg (95% CI -0.8 to 0.9); or hand function, 0.7 points (95% CI -3.6 to 5.0). While both groups improved, neither regimen is superior to the other in patients with trapeziometacarpal osteoarthritis.