Background: Balneotherapy is used as a treatment modality for various musculoskeletal disorders. The aim of this study was to evaluate the effectiveness of intermittent balneotherapy in patients with knee osteoarthritis (OA). Methods: Seventy-two patients with knee OA were included in the study. Patients were divided into two groups: group A (48 patients) was given intermittent once weekly treatment for 6 weeks; group B (24 patients) served as a control group. Evaluation was done prior to study entry, at weeks 4 and 6, and 4 weeks following completion of treatment (week 10). Assessment included global pain score (VAS), WOMAC index, Lequesne's functional index, patients' and physician's disease severity score, and NSAID/analgesic consumption. Results: Following balneotherapy, a statistically significant improvement, determined by the reduction in the mean changes of most outcome parameters (VAS, WOMAC, and Lequesne's index), was noted in group A at weeks 4 and 6 and was sustained 4 weeks after cessation of treatment (week 10). Significant improvement in both physician's and patients' disease severity scores, as well as a reduction in analgesic and NSAID consumption, were also noted in group A. No improvement was found in the control group in any of the tested parameters. Conclusions: Intermittent balneotherapy appears to be effective in the treatment of knee OA.