Sphaeralcea angustifolia Cavanilles & Don (Malvaceae), known in Mexico as "Vara de San José", is used in Mexican Traditional Medicine as an anti-inflammatory and, more specifically, for treating rheumatism. Anti-inflammatory properties have been demonstrated in different pharmacological models. The therapeutic effectiveness and tolerability of the topical administration of a gel elaborated with a standardized Sphaeralcea angustifolia extract applied to patients with Hand osteoarthritis (HOA) was evaluated. A pharmaceutical formulation in a gel presentation that contained a standardized extract (hydroxycoumarin content) of Sphaeralcea angustifolia was elaborated and later evaluated in a double-blind, randomized study controlled with a similar formulation containing 2% diclofenac. Treatments were administered topically for 4 weeks on the affected hand(s). Clinical evolution was followed weekly by means of the Algofunctional Index (AFI) and the Visual Analog Scale (VAS). A total of 130 participants were included in the study. Among these, 113 were considered in the analysis (55 in the experimental group and 58 in the control group). In both groups, important improvement in the patients' symptomatology was noted. Therapeutic effectiveness was 89% and 91.3% in the two groups, respectively, without a statistically significant difference between the groups. None of the treatments presented any adverse effects. The 4-week topical administration of a gel formulation elaborated with a 1% standardized extract of Sphaeralcea angustifolia showed therapeutic effectiveness and tolerability when administered to patients with HOA, without exhibiting significant differences when compared with the effect observed in patients treated with 2% diclofenac. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.