Spondyloarthritis, notably ankylosing spondylitis (AS), represents a chronic rheumatic condition typified by persistent back pain and stiffness. It constitutes a substantial portion of diagnoses within rheumatology units and exhibits a higher prevalence among males. Diagnosis relies upon comprehensive clinical evaluation, including patient history, physical examination, and adjunctive radiological assessments, with genetic predisposition, particularly the presence of the HLA-B27 antigen, playing a significant role.

Management strategies encompass a multidisciplinary approach, with physiotherapy emerging as a cornerstone therapeutic modality. Various exercise interventions, particularly those supervised by trained professionals, demonstrate efficacy in improving pain, stiffness, and overall functional capacity. Furthermore, patient education plays a pivotal role in enhancing treatment adherence and optimizing outcomes by aligning patient expectations with therapeutic goals.

The evolving landscape of spondyloarthritis management underscores the necessity of further research into multimodal treatment approaches, particularly in integrating novel interventions such as electrophysical agents. By elucidating the mechanisms of action and exploring their synergistic effects, clinicians can refine treatment protocols and ultimately enhance the quality of care provided to individuals living with spondyloarthritis.

Spondyloarthritis or ankylosing spondylitis (AS) is a type of chronic spondyloarthropathy. According to the Spanish Society of Rheumatology (SER), spondyloarthropathies constitute a heterogeneous family of interrelated rheumatic diseases that share clinical, pathogenic, genetic, radiological, epidemiological and therapeutic response characteristics. From an epidemiological point of view, they are increasingly frequent diseases, accounting for more than 13% of patients diagnosed in rheumatology units. Specifically, international reference studies place AD as the most frequent, with an estimated incidence of 7 new cases per 100,000 inhabitants per year. It is more frequent in men than in women (in a ratio of 3:1) and the age range is between 20 and 30 years. In Extremadura the incidence is no less. According to the National Institute of Statistics (INE), there are currently 24 cases per 1000 people diagnosed with rheumatoid arthritis or AD, and 55 cases per 1000 people diagnosed with arthritis.

In terms of clinical manifestations, early symptoms include back pain and stiffness. Over time, AS can fuse vertebrae and limit movement, causing severe and constant pain. Diagnosis and follow-up of the disease is based on clinical history and physical examination. Radiological tests may also be used to complement the diagnosis. Over the years, the concept of spondyloarthropathy has evolved, and is now defined as a combination of axial spondyloarthritis (SpA), psoriatic arthritis (PsA) and inflammatory bowel disease (IBD).

With regard to the criteria according to the Assessment of Spondyloarthritis International Society (ASAS) and the latest update of the Clinical Practice Guideline for the treatment of SpA and psoriatic arthritis, within SpA the investigators find AD as the most representative pathology of this group, being the one the investigators will focus on in this research project.

The diagnosis of axial SpA requires: a) imaging evidence confirming sacroiliitis and b) at least one sign of SpA or HLA-B27 marker and two of the signs determined according to ASAS (inflammatory low back pain, arthritis, enthesitis, uveitis, dactylitis, psoriasis, Crohn's disease, good response to NSAIDs, family history of SpA, presence of HLA-B27 antigen or presence of increased C-reactive protein). In this regard, in addition to imaging and laboratory tests, the International Society for the Evaluation of SpA classification considers common clinical features as the main diagnostic axis.

Based on the latest SER review, the mechanism by which the disease occurs is still not entirely clear, although there is a genetic predisposition. Among the factors involved, the most important is the presence of the positive HLA-B27 antigen, which is present in the vast majority of patients with AD and less frequently in the rest of the diseases of the SpA group. Taking into account that only 10% of HLA-B27 antigen carriers will present with the disease, it is essential to present clinical signs to support the diagnosis.

According to the best available scientific evidence, physiotherapy is the main effective rehabilitation treatment measure for patients with SpA, and specifically for the most widespread form of the disease such as AD.

Several rehabilitation modalities exist, although, to date, there is limited consensus on a sequenced and standardised protocol. The review analysed 28 studies in which at least one intervention group received physiotherapy treatment. A total of 1926 subjects with AS were analysed, with pain, stiffness, mobility (spine and chest wall) and physical function (disease activity, ABVD and global function) being the main variables studied.

The results reported that doing physiotherapy through therapeutic exercise performed by physiotherapists is better than doing nothing. Within the exercise modalities, supervised exercise by external control or focus is showing better results in regulating pain modulatory mechanisms, also improving pain intensity, range of motion and perceived disability in subjects with spinal pathology.

On the other hand, electrophysical agents have also been routinely applied in subjects with spinal pathology, as they are inexpensive procedures with no reported adverse effects and can be easily accessible to the general population. Among these, transcutaneous electrical stimulation procedures with TENS-type currents stand out. This modality is applied via adhesive electrodes placed on the skin or on the affected nerve in question, as well as those that use medium-frequency interferential currents, showing clinical efficacy in reducing perceived pain. However, there are limited studies that apply these interventions in subjects diagnosed with AD, and as far as the authors of this project are aware, there are no clinical trials that analyse the effects of combining both interventions in a multimodal programme.

On the other hand, there are studies that demonstrate the importance of satisfaction as an influential factor in both the clinical benefits and the quality of the health care provided. If the investigators focus exclusively on the field of physiotherapy, similar benefits have been reported between those who receive an educational briefing and those who receive a standardised physiotherapy treatment without adequate information. Accurate information about the disease in question and about the stages of treatment will therefore ensure that the user's expectations are in line with reality, favouring overall satisfaction and adherence to treatment.

In this context, there has been a growing interest in analysing multimodal physiotherapy programmes in the approach to chronic musculoskeletal pathology.

Inclusion Criteria:

• Adults (men and women) over 18-65 years of age.
• Diagnosed with ankylosing spondylitis by a rheumatologist.

Exclusion Criteria:

• Sample subjects with spinal surgery in the last 12 months were excluded.
• Subjects with mild/moderate cognitive impairment (score ≥24 in the Spanish validated version for general older adults of the Mini-Mental State Examination) (Lobo A, Saz P, Marcos G et al. Revalidation and standardisation .
• Finally, those with pharmacological treatment that could generate vestibular or balance disturbances at the time of assessment and treatment.