Patients assigned to this group will receive a session of manual therapy and therapeutic exercise. The manual therapy (TM) treatment for tendinopathies is mainly focused on soft tissue mobilization and deep transverse friction massage (Cyriax).

The therapeutic exercise session participants will perform 2 exercises for 4 weeks 3 days per week. The first exercise they will perform will be the Short-Foot Exercise holding the position 5 seconds isometrically. The second exercise will be plantar flexion of the ankle with adduction of the foot and inversion with elastic band in its concentric and eccentric phase. Each exercise will be performed in 3 series of 15 repetitions, with 1 minute rest between series, the exercise session will follow the TM and will last approximately 15-20 minutes.

Participants in this group will receive 4 sessions (once a week during their respective treatment session) of percutaneous electrolysis guided by MUSCULO-SKELETAL ECOGRAPHY, by a physiotherapist with extensive clinical experience in this therapeutic approach. The technique will be applied using a specifically developed and medically certified device (EPI Advanced Medicine®, Barcelona, Spain. EPI®). The galvanic current will be applied using acupuncture needles. In the present study, a 0.30*25 mm needle (Agupunt, Barcelona, Spain) will be used, with an intensity of 2 mA for a total of 3-5 seconds and 3-5 impacts on the liquid content (TTP tenosynovitis) and 2 mA for a total of 3 seconds and 2-3 impacts if in the tendon (intrasubstance). The technique shall be applied under ultrasound guidance.

The needle shall be introduced at an angle of 80° in a short-axis cross-section to the skin, with the tip of the needle directed towards the posterior tibial tendon.

Electrolysis is the process by which water (H2O) and sodium chloride (NaCl) molecules, which are present in the biological tissues and body compartments of our organism, are organically broken down into their constituent chemical elements, regrouping to create entirely new substances such as sodium hydroxide (NaOH), hydrogen gas (H2) and chlorine gas (Cl2). This process occurs thanks to the passage of a flow of direct electric current, also known as galvanic current, which is a totally athermal process. The passage of this current allows a local inflammatory response to occur (increase in lymphocytes and macrophages) as well as an increase in vasodilatation, inducing phagocytosis and biological stimulation of tendon repair.

The scale consists of a horizontal line of 11 numbers, at the ends of which are the extreme manifestations of a symptom that allows observers to measure the intensity of pain with maximum reproducibility. On the far left is 0 or the total absence of pain and on the far right is 10 or the maximum pain that can be tolerated. The patient will be asked to select the number where they consider their pain to be.

The FAAM questionnaire consists of 29 items separated into two subscales: the ADL subscale with 21 items and the Sport subscale with 8 items. Each one has a maximum Likert scale score of 5 points ranging from "no difficulty" to "impossible to perform". All scores will be converted to percentages, with a higher percentage indicating a higher level of functionality and lower pathology. At the end of the scale, the functionality percentage will be calculated, ranging from 0% (inability to perform any activity) to 100% (normal functionality level). Finally, patients will rate the condition of their ankle and foot on a 4-point scale that includes "normal," "almost normal," "abnormal," and "severely abnormal." The intention of the study is that the patient recovers 100% of functionality or better the percentage that has been marked prior to the intervention. As in the 4-point scale, the condition of your ankle should be normal.

All participants, both in the control and experimental groups, will be examined before the intervention and at the end of the 4 sessions to evaluate possible changes in the tendon, and all invasive interventions will be performed ultrasonographically. This measurement was just a qualitative control of the diagnosis of tendinopathy.