OBJECTIVE:

To compare the benefits of a thermal cure and non-thermal rehabilitation in treatment of knee osteoarthritis (KOA).

METHODS:

Randomized therapeutic trial including patients with knee osteoarthritis (American College of Rheumatology criteria). Patients were randomly divided into two groups. Spa treatment consisted of underwater shower, massage-jet showers, hydromassage, pool rehabilitation and peloid therapy. Non-thermal rehabilitation consisted of analgesic physiotherapy, muscle strengthening and group physical rehabilitation. A blinded evaluation was carried out at day 21 and 12months following treatment. It was based on the visual analogic scale of pain (VAS), which represented the primary endpoint.

RESULTS:

Two hundred and forty patients were included (February-June 2005). The spa treatment and non-thermal rehabilitation groups included 119 and 121 patients respectively. Two hundred and thirty-three patients completed their treatments. Significant improvement of the visual analogic scale of pain was noted in the thermal cure group (61.6±15 at day 0 versus 46.5±22.4 at 12months, P<0.001), but not in the non-thermal group (64.1±15 at day 0 versus 62±29 at 12months, P=0.68). At day 21, comparison of the two groups revealed no significant difference on the VAS (P=0.08). However, at 12months, the thermal cure group was significantly more improved (P=0.000).

CONCLUSION:

In our study, crenobalneotherapy had resulted, at 12months, in more pronounced long-term improvement of the painful symptoms of KOA than had non-thermal rehabilitation.

1.1. Introduction

Osteoarthritis is the most common rheumatic disease. It originates in mechanical and biological phenomena that induce focal alterations of the articular cartilage and subchondral bone remodeling [1]. The knee joint is the most frequent location of osteoarthritis [1]. Its prevalence increases with age [2]. Osteoarthritis entails considerable functional discomfort and impairment because of pain as well as movement limitations that can bring out invalidity or aggravate disability. It represents a major public health problem due to its impact on the quality of life and its substantial socio-economic cost. The objectives of osteoarthritis management are to attenuate pain while improving mobility and the functional capacities of the patient. As non-medical adjuvant treatments, the role of thermal cures is far from clear. Even though the application of thermo-mineral waters or hot springs for therapeutic purposes is a highly ancient and widespread practice in rheumatology, it has up until now been the subject of only a limited number of evaluations and medical publications.

In Tunisia, the history of thermal waters goes back more than two thousand years; during the epoch of the Roman Empire, recourse to hot waters was already current. Tunisian thermal springs are numerous and have traditionally been commercialized as thermal “hammams” and, more recently, as part and parcel of modern medical facilities. The Tunisian office of thermalism estimates that in 2012, 3.3 million spa visitors attended the country's thermal baths [3].

In this paper, we report on the results of a randomized therapeutic trial aiming at comparing the benefits, with regard to knee osteoarthritis symptoms, of a thermal cure and a rehabilitative treatment, both of which were conducted in the same spa center on the southern Tunisian island of Djerba.

1.2. Patients and methods

1.2.1. Inclusion criteria

Patients with knee osteoarthritis (KOA) meeting the diagnostic criteria of the American College of Rheumatology (ACR 1992). In addition, KOA had to be symptomatic, as defined by a visual analog scale (VAS) score higher than 30 and by a Lequesne algofunctional index (AFI) score higher than 5.

1.2.2. Exclusion criteria

Subjects presenting with a loss of autonomy necessitating the assistance of another person or with diminished intellectual capacities, as well as those presenting with contraindications to a thermal cure (infectious pathology, poorly controlled hypertension, decompensated cardiopathy, progressive cancer, progressive inflammatory disease, decompensated psychiatric disorder or age greater than 75 years). Other reasons for exclusion were: patients presenting with an inflammatory outbreak of KOA, having recently (within 30 days) undergone intra articular infiltration or suffering from surgical KOA (IAF > 15, walking distance < 1000 m, limitation of flexion to less than 90°), having a rheumatologic disease likely to interfere with measured indices (symptomatic arthropathy of the ankle or the foot, radicular pain) and finally, using stage 3 analgesics (WHO classification).

The baseline visit (D0) took place at least one week before the cure. Selection of the patients who would referred to the spa center was carried out from among the persons consulting at the rheumatology department of Mongi Slim hospital, a Tunis-based university medical center operating independently from the spa center. At that time, the investigating physicians (5 rheumatologists from Mongi Slim hospital and 1 rheumatologist from the spa center in Djerba) verified the inclusion criteria and asked the patients to sign an informed consent form, in its Arabic or French version according to their choices.

All relevant demographic data and clinical history were collected during the initial visit. Finally, anteroposterior and lateral radiographs of the knees were performed in all the patients.

While balneotherapy has been cited by the OARSI (the Osteoarthritis Research Society International) as a therapeutic means of KOA [10] and is of proven, it has not been included in the recommendations issued by the ACR [11] or the European League Against Rheumatology (EULAR) [12] and [13]. This omission has essentially to do with the difficulty of conducting rigorous clinical trials on therapies not involving drugs. Retrospective and open studies do not methodologically suffice to corroborate the alleged benefits of thermal treatment.

As concerns the analysis grid evaluating the internal validity of non-pharmacological trials (CLEAR grid) [14], Forestier et al., have underlined their frequently mediocre quality from the standpoint of methodology and/or statistical analysis; as a result, it is not easy to validate the observed differences that would appear to favor balneotherapy [6].

Moreover, it is particularly difficult to blind patients in placebo-controlled studies. In our study, a certain degree of patient blindness was achieved because randomization involved groups of patients who had no information on the type of treatment applied to the others, which meant that risk of disappointment bias was reduced [4].

The second difficulty lies in the fact that the benefits of thermal treatment are partially attributed to a “cure effect” brought about by physical repose and a salutary break with the usual environment, while only therapeutic abstention or a home-based medical treatment have been proposed to the control group. Wishing to remedy this difficulty, we have compared the effects of thermal treatments to those of non-thermal physical rehabilitation treatment, with the two types of therapies being delivered at the same center and with the same accommodations being provided for stays of identical duration. In our study, we were indeed able to limit the impact of the “cure effect” with regard to the differences in effectiveness observed in the thermal cure group as opposed to the control group.

Another difficulty is related to the diversified characteristics of the thermal springs (richness in minerals or trace elements, natural radioactivity, heat) and the likewise diversified thermal care protocols. That much said, our protocol was similar to the standard protocols applied in European balneotherapy centers.

A non-comparative method of prolonged observation of a cohort with repeated measurements allows for circumvention or avoidance of the above-mentioned difficulties. In fact, this method is classified in the international literature as a quasi-experimental research design and is applied each time a randomized and blinded method cannot be used given the nature of the treatment to be evaluated, as it is clearly the case with thermal care [15]. Comparative methods with randomization are nevertheless considered as the most conclusive. To our knowledge, our study is the first to have compared thermal to non-thermal physical rehabilitation, both of which had been carried out in the same center.

The interest of some randomized studies may be reduced by a limited number of participants, insufficient critical distancing or recruitment of a sample of non-representative patients. In addition to its prospective nature, our study is distinguished by a consequential scale of participation and the prolonged duration of medical follow-up, which was carried on until 12 months after the end of the cure.

1.6. Conclusion

Our study suggests that a thermal cure has greater effectiveness than non-thermal rehabilitation with regard to the pain component of KOA. On the other hand, the confirmed superiority of physical as opposed to thermal treatment with regard to the function component of KOA suggests the interest of adding, on a track parallel to that of the thermal cure protocol, a rehabilitative program of muscle strength reinforcement that could optimize the results of thermal treatment.

Disclosure of interest

The authors declare that they have no conflicts of interest concerning this article.