We present a unique prospective study to estimate the median sustained stage-related improvement in pain and hand function in patients with trapezio-metacarpal joint osteoarthritis after administration of a single corticosteroid injection. Response to the corticosteroid injection was assessed using Disability of Arm Shoulder and Hand (DASH) and Visual Analogue Scale (VAS) pain scores. Self assessment scores revealed a reduction in pain and improvement in hand function. All patients reported a significant improvement in pain and hand function (p </= 0.05), regardless of the disease stage. Additionally, we observed a marked difference in the duration of improvement in hand function between early and late stages of the disease (p = 0.0046). In conclusion, it is possible to predict the period of symptomatic improvement at each of the four radiological stages of the disease. This would allow the treating clinician to judge the outcome of treatment with reasonable accuracy.