Several studies have demonstrated that matrix metalloproteinases (MMPs) are frequently implicated in the destruction of articular cartilage in arthritis. The control of MMP activity is dependent on the local concentration of tissue inhibitors of metalloproteinases (TIMPs), and the imbalance of the enzyme-to-inhibitor ratios plays an important role in the remodeling of articular tissues. Some cytokines such as interleukin (IL)-1 and tumor necrosis factor (TNF)-alpha which regulate leukocyte activities, promote MMP secretion and, as a consequence, cartilage degradation. The aim of the present study was to investigate whether a natural treatment is effective in reducing cartilage inflammation and degradation by influencing MMP and TIMP serum levels. Eighty patients with osteoarthritis (OA) were enrolled in the trial and were divided into group A (30 patients who did not undergo mud bath therapy), group B (28 patients repeating mud bath therapy more than 5 times and less than 10) and group C (22 patients repeating mud bath therapy more than 10 times). Blood samples were obtained from all the patients for assay of MMP-1, -2, -3, -8 and -9 and TIMP-1 and -2. The parameters were determined by an ELISA technique. Statistical indexes were calculated for each parameter and mean values were compared. The differences between mean values of MMP-3, -8 and -9 were statistically significant between group A and the treated groups (B and C). Analysis of variance established a significant difference (p < 0.05) between groups A and C in mean serum levels of MMP-8, MMP-9 showed a statistically significant difference (p < 0.05) in mean serum concentration between groups A and B. Regression analysis showed a very high R2 between MMP-2 and TIMP-2. One of the most interesting findings in this study was that MMP-3 serum levels were significantly lower in the treated groups, since this enzyme plays an important role in cartilage degradation, suggesting that mud bath therapy contributes to matrix integrity in OA cartilage. In contrast, MMP-8 and -9 were higher in the treated subjects and no correlation with TIMPs was evident. One possible explanation is that these enzymes are required for the efficient degradation and removal of already compromised cartilage matrix and that they operate as part of a matrix turnover and repair process. In conclusion, our data suggest that mud bath therapy alone is not able to influence chondrocyte metabolic activity in the advanced phases of OA. There could be a synergic and sequential association with pharmacologic therapy and/or interventions.