Achilles tendinopathy is a condition characterized by inflammation of the Achilles tendon. Achilles tendinopathies are classified into insertional tendinitis and noninsertional tendinitis. Insertional tendinitis involves the lower part of the tendon, where the tendon inserts at the level of the calcaneus, and can affect even patients who are not particularly athletically active. Noninsertional tendinitis occurs when the fibers in the middle portion of the tendon are affected, affects young and athletic people the most, and has a high incidence (30-50%) in middle-aged individuals.

Considering that there are no strong evidence-based guidelines in the area of treatment of achilles tendinopathy, the aim of this research project is to understand through a multicenter, randomized clinical investigation the impact of treatment with a porcine collagen-based medical device administered in the peri-tendon area in combination with physiotherapy on pain reduction and functional improvement of the investigated tendon.

In view of the morpho-structural changes that characterize Achilles tendinopathy, the use of injectable medical devices such as Collagen Medical Devices might find therapeutic indication. For some years now, in fact, the use of injectable medical devices based on porcine collagen and ancillary substances of natural origin (Collagen Medical Devices GUNA) has been introduced in the treatment of painful and degenerative pathologies of the locomotor system, which allow a more effective and specific placement of collagen in situ with the function of vehiculation and stabilization.

The purpose of this research project is to understand through a multicenter, randomized clinical study investigation the impact of treatment with a porcine Collagen-based Medical Device called MD-Tissue, administered in the peri-tendon area, in combination with physiotherapy on pain reduction and functional improvement of the investigated tendon.

The multicenter, randomized clinical investigation is prospective, and will have a total duration of 8 weeks.

After enrollment, subjects will be randomized and assigned to two experimental groups:

• Group A which, alongside physiotherapy (eccentric strengthening protocol) will receive MD-Tissue Collagen Medical Device.
• Group B which, will implement only physiotherapy (eccentric strengthening protocol).

Variables will be assessed at baseline (T0 time), after 1 week (T1), after 2 weeks (T2), after 3 weeks (T3), at the end of the injection treatment, and 6 weeks after enrollment (T6/FU). A further evaluation will be carried out after 2 weeks and after 8 weeks T8/FU from the start of the investigation study.

After enrollment, subjects in both groups will begin a physiotherapy course (eccentric strengthening protocol), lasting 6 weeks. Each session will consist of stretching exercises of the Achilles tendon.

Inclusion Criteria:

• Male and female subjects aged 18 to 70 years;
• Subjects with tendon pain for not more than 24 weeks;
• Subjects with clinically diagnosed and ultrasonographically confirmed insertional/noninsertional/mystic tendinopathy;
• Subjects with a VISA A score between 50 and 75;
• VAS ≥ 5;
• Subjects able to understand and answer the SF12 questionnaire;
• Subjects able to understand and sign the informed consent.

Exclusion Criteria:

• subjects who have had surgery in the investigated area or lower extremity;
• subjects who have previously undergone physiotherapy.
• subjects with autoimmune diseases;
• subjects with peripheral neuropathy;
• subjects with calcific tendinopathy
• subjects with pain of direct traumatic origin;
• subjects with local/systemic infections;
• subjects with neoplastic diseases;
• subjects with gout;
• subjects on corticosteroid treatment at the time of enrollment;
• subjects who have used corticosteroids or fluoroquinolones in the three months prior to enrollment;
• subjects who have used NSAIDs in the week prior to enrollment;
• subjects who are pregnant and lactating;
• subjects with contraindications to acetaminophen use;
• allergy to porcine collagen.