A systematic review and meta-analysis of the effect of spa therapy on knee osteoarthritis

Introduction Osteoarthritis (OA) is a frequent chronic condition leading to disability that affects approximately 10% of people over 60 years with a significant impact on the quality of life. Treatment of OA is based on pharmacological and non-pharmacological measures. These include the use of SPA therapy (comprises a broad spectrum of therapeutic modalities including hydrotherapy, balneotherapy, mud-pack therapy, mud-bath therapy, massage and exercise). The biological effects of mud-bath therapy in osteoarthritis are mainly secondary to heat stimulation and to physico-chemical properties and biological composition of waters and peloids. Mud-bath therapy likely exerts its effects modulating several cytokines, chemokines, metalloproteases, adipokines and other important molecules involved in inflammation, cartilage degradation. Our aim was to perform an updated meta-analysis on the effect of spa therapy (in particular mud-bath therapy on knee osteoarthritis, is among the most common and disabling forms of OA with high socio-economic impact. Methods A MEDLINE on PubMed for articles on knee OA and spa therapy published up to march 2019 was performed. Articles were included if trials were comparative, if one or more of the subgroups had knee OA with separate data, and if spa therapy or any hydrotherapy techniques involving mineral water or mineral mud was compared to any other intervention or no treatment. We removed all the articles that were not related to OA and to Spa therapy and all the narrative or systematic reviews, the case reports, the open studies and studies of water exercises performed without mineral water by reading the titles and abstracts. Data were extracted from the full text and then reviewed. We examined Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at the end of each study of intervention in the selected studies and VAS pain between experimental groups vs control groups as primary endpoints. Mean values and standard deviations (SD), or test statistics were recorded for each of the selected study, and effect sizes were computed using the standardised mean difference (SMD) technique. Sample size and effect sizes were processed with the MedCalc software package. Results The flow-chart of articles is described in Fig.1. We found 4 references with low risk of bias (n = 769 patients), 17 with median risk (n = 1105 patients). We excluded articled with high risk of bias. The funnel plot reporting estimation of heterogeneity and publication bias across studies due to short and heterogeneous follow-up timing is reported in Fig. 2. There was a significant improvement in WOMAC in all studies but for 4, thus suggesting that these results seem to confirm the beneficial effect of SPA therapy on WOMAC indices in patients with knee OA (Fig. 3). An analogous improvement of VAS pain has been also observed (Fig. 4). The review also confirms that mud-bath therapy has some beneficial effects on the reduction of the use of analgesics and NSAIDs. Conclusions Spa therapy is an effective remedy in reducing pain and functional limitation compared to minimal or no interventions in patients with knee osteoarthritis. SPA therapy is a non invasive, complication-free, and cost-effective alternative modality for the conservative treatment of knee osteoarthritis. It cannot substitute for conventional therapy but can complement to it. For what concern the different modalities of spa therapy we can’t state the superiority of one of these techniques over another one, because there is a lack of studies that compare these different spa approaches. Indications based on the clinical guidelines of the French National Authority suggest that patients with knee osteoarthritis might gain the benefit of a persistent improvement of pain. In the OARSI guidelines for the nonsurgical management of knee osteoarthritis, balneotherapy was considered appropriate only for the subphenotype multiple-joint OA with co-morbidities.