Carpometacarpal osteoarthritis (CMC-OA) is a disabling condition, characterized by pain and functional impairment. The aim of the present study is to evaluate the efficacy of a single ultrasoundguided injection of hyaluronic acid (HA) in patients suffering from CMC-OA. Eighteen patients with CMC-OA, grade 2-3 Kellgren and Lawrence score, attending the Orthopaedic Department of the University Hospital of Chieti, were enrolled. They underwent clinical evaluation at baseline and after one month follow-up, evaluating: grading of pain (VAS at rest and during activities), function (Dreiser Index), grip and pinch strengths Jamar dynamometer), as well as NSAIDs consumption. Each patient received a single ultrasound- guided injection of HA into the articular CMC joint. The results were that pain at rest and during activities decreased from 1.8 +/= 1.07 to 0.5 +/= 0.68 (p < 0.001) and from 8.05 +/= 0.94 to 4.15 +/= 1.42 (p < 0.001), respectively. Dreiser Functional Index showed a significant improvement (+11.59 percent; p < 0.004), as well as pulp pinch strength (24.07 percent; p < 0.001). The consumption of NSAIDs was also clearly reduced, from 16 to 7 patients (-45 percent) and from 2.45 +/= 1.98 to 1.15 +/= 1.30 tablets per week (p < 0.02). Mild local side effects, lasting less than 3 hours, were observed only in 2 cases. A single ultrasound guided injection of HA is a safe and effective procedure in CMC-OA, with a significant improvement in terms of pain and function. However, studies with larger samples and longer term follow-up are warranted.